r_draw.c

/* Emacs style mode select   -*- C++ -*-
 *-----------------------------------------------------------------------------
 *
 *
 *  PrBoom: a Doom port merged with LxDoom and LSDLDoom
 *  based on BOOM, a modified and improved DOOM engine
 *  Copyright (C) 1999 by
 *  id Software, Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
 *  Copyright (C) 1999-2000 by
 *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
 *  Copyright 2005, 2006 by
 *  Florian Schulze, Colin Phipps, Neil Stevens, Andrey Budko
 *  Copyright 2023, 2024 by
 *  Frenkel Smeijers
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 *  02111-1307, USA.
 *
 * DESCRIPTION:
 *      Rendering main loop and setup functions,
 *       utility functions (BSP, geometry, trigonometry).
 *      See tables.c, too.
 *
 *-----------------------------------------------------------------------------*/

#include <stdint.h>

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "compiler.h"
#include "d_player.h"
#include "w_wad.h"
#include "r_main.h"
#include "r_things.h"
#include "m_fixed.h"
#include "st_stuff.h"
#include "i_system.h"
#include "g_game.h"
#include "m_random.h"

#include "globdata.h"


// Silhouette, needed for clipping Segs (mainly)
// and sprites representing things.
#define SIL_NONE    0
#define SIL_BOTTOM  1
#define SIL_TOP     2
#define SIL_BOTH    3

typedef struct drawseg_s
{
  const seg_t __far* curline;
  int16_t x1, x2;
  fixed_t scale1, scale2, scalestep;
  int16_t silhouette;                       // 0=none, 1=bottom, 2=top, 3=both
  fixed_t bsilheight;                   // do not clip sprites above this
  fixed_t tsilheight;                   // do not clip sprites below this

  // Pointers to lists for sprite clipping,
  // all three adjusted so [x1] is first value.

  int16_t *sprtopclip, *sprbottomclip;
  int16_t *maskedtexturecol; // dropoff overflow
} drawseg_t;

#define MAXDRAWSEGS   192

static drawseg_t _s_drawsegs[MAXDRAWSEGS];


#define MAXOPENINGS (VIEWWINDOWWIDTH*16)

static int16_t openings[MAXOPENINGS];
static int16_t* lastopening;


static const int8_t viewangletoxTable[2027];

static int8_t viewangletox(int16_t va)
{
#ifdef RANGECHECK
	if (va < 0)
		I_Error("viewangletox: va < 0: %i", va);
	else if (va >= 4096)
		I_Error("viewangletox: va >= 4096: %i", va);
#endif

	if (va < 1046)			//    0 <= va < 1046
		return VIEWWINDOWWIDTH;
	else if (3073 <= va)	// 3073 <= va < 4096
		return 0;
	else					// 1046 <= va < 3073
		return viewangletoxTable[va - 1046];
}


static const angle_t tantoangleTable[2049];
static const angle16_t* tantoangle16Table = ((angle16_t*)&tantoangleTable[0]) + 1;

#define tantoangle(t) tantoangleTable[t]
#define tantoangle16(t) tantoangle16Table[(t)*2]


static const uint16_t finetangentTable_part_3[1024];
static const fixed_t  finetangentTable_part_4[1024];

static int16_t floorclip[VIEWWINDOWWIDTH];
static int16_t ceilingclip[VIEWWINDOWWIDTH];


static int16_t screenheightarray[VIEWWINDOWWIDTH] =
{
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,

	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT,
	VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT, VIEWWINDOWHEIGHT
};

static int16_t negonearray[VIEWWINDOWWIDTH] =
{
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,

	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1
};


//*****************************************
//Globals.
//*****************************************

int16_t numnodes;
const mapnode_t __far* nodes;

fixed_t  viewx, viewy, viewz;

angle_t  viewangle;
static angle16_t viewangle16;

static byte solidcol[VIEWWINDOWWIDTH];

static const seg_t     __far* curline;
static side_t    __far* sidedef;
static const line_t    __far* linedef;
static sector_t  __far* frontsector;
static sector_t  __far* backsector;
static drawseg_t *ds_p;

#if defined FLAT_SPAN
static int16_t floorplane_color;
static int16_t ceilingplane_color;
#else
static visplane_t __far* floorplane;
static visplane_t __far* ceilingplane;
#endif

static angle16_t             rw_angle1;

static angle16_t         rw_normalangle; // angle to line origin
static int16_t         rw_distance;

static int16_t      rw_stopx;

static fixed_t  rw_scale;
static fixed_t  rw_scalestep;

static int32_t      worldtop;
static int32_t      worldbottom;

static boolean didsolidcol; /* True if at least one column was marked solid */

static boolean  maskedtexture;
static int16_t      toptexture;
static int16_t      bottomtexture;
static int16_t      midtexture;

static fixed_t  rw_midtexturemid;
static fixed_t  rw_toptexturemid;
static fixed_t  rw_bottomtexturemid;

const uint8_t __far* fullcolormap;
const uint8_t __far* fixedcolormap;

static int16_t extralight;                           // bumped light from gun blasts


static int16_t   *mfloorclip;   // dropoff overflow
static int16_t   *mceilingclip; // dropoff overflow
static fixed_t spryscale;
static fixed_t sprtopscreen;

static angle16_t  rw_centerangle;
static int16_t  rw_offset;
static int16_t      rw_lightlevel;

static int16_t      *maskedtexturecol; // dropoff overflow

int16_t   __far* textureheight; //needed for texture pegging (and TFE fix - killough)

int16_t       __far* texturetranslation;

fixed_t  viewcos, viewsin;

static fixed_t  topfrac;
static fixed_t  topstep;
static fixed_t  bottomfrac;
static fixed_t  bottomstep;

static fixed_t  pixhigh;
static fixed_t  pixlow;

static fixed_t  pixhighstep;
static fixed_t  pixlowstep;

static int32_t      worldhigh;
static int32_t      worldlow;


uint16_t validcount = 1;         // increment every time a check is made

//*****************************************
// Constants
//*****************************************

static const int16_t CENTERX = VIEWWINDOWWIDTH  / 2;
       const int16_t CENTERY = VIEWWINDOWHEIGHT / 2;

static const fixed_t PROJECTION = (VIEWWINDOWWIDTH / 2L) << FRACBITS;

static const int16_t PSPRITESCALE  = FRACUNIT * VIEWWINDOWWIDTH / SCREENWIDTH_VGA;
static const fixed_t PSPRITEISCALE = FRACUNIT * SCREENWIDTH_VGA / VIEWWINDOWWIDTH; // = FixedReciprocal(PSPRITESCALE)

static const uint16_t PSPRITEYSCALE = FRACUNIT * (VIEWWINDOWHEIGHT * 5 / 4) / SCREENHEIGHT_VGA;
static const fixed_t PSPRITEYISCALE = FRACUNIT * SCREENHEIGHT_VGA / (VIEWWINDOWHEIGHT * 5 / 4); // = FixedReciprocal(PSPRITEYSCALE)

static const angle16_t clipangle = 0x2008; // = xtoviewangleTable[0]


#if defined __WATCOMC__
//
#else
inline
#endif
fixed_t CONSTFUNC FixedMul(fixed_t a, fixed_t b)
{
	uint16_t alw = a;
	 int16_t ahw = a >> FRACBITS;
	uint16_t blw = b;
	 int16_t bhw = b >> FRACBITS;

	if (bhw == 0) {
		uint32_t ll = (uint32_t) alw * blw;
		 int32_t hl = ( int32_t) ahw * blw;
		return (ll >> FRACBITS) + hl;
	} else if (alw == 0) {
		//return ahw * b;
		 int32_t hl = ( int32_t) ahw * blw;
		 int32_t hh = ( int32_t) ahw * bhw;
		return hl + (hh << FRACBITS);
	} else {
		uint32_t ll = (uint32_t) alw * blw;
		 int32_t hl = ( int32_t) ahw * blw;
		return (a * bhw) + (ll >> FRACBITS) + hl;
	}
}


inline static fixed_t CONSTFUNC FixedMul3232(fixed_t a, fixed_t b)
{
	uint16_t alw = a;
	 int16_t ahw = a >> FRACBITS;
	uint16_t blw = b;
	 int16_t bhw = b >> FRACBITS;

	uint32_t ll = (uint32_t) alw * blw;
	 int32_t hl = ( int32_t) ahw * blw;
	return (a * bhw) + (ll >> FRACBITS) + hl;
}


//
// FixedMulAngle
// b should be coming from finesine() or finecosine(), so it's high word is either 0x0000 or 0xffff
//
#if defined __WATCOMC__
//
#else
inline
#endif
fixed_t CONSTFUNC FixedMulAngle(fixed_t a, fixed_t b)
{
	uint16_t alw = a;
	 int16_t ahw = a >> FRACBITS;
	uint16_t blw = b;

	uint32_t ll = (uint32_t) alw * blw;
	 int32_t hl = ( int32_t) ahw * blw;
	fixed_t r = (ll >> FRACBITS) + hl;

	if (b < 0)
		r -= a;

	return r;
}


#if defined __WATCOMC__
//
#else
inline
#endif
fixed_t CONSTFUNC FixedMul3216(fixed_t a, uint16_t blw)
{
	uint16_t alw = a;
	 int16_t ahw = a >> FRACBITS;

	uint32_t ll = (uint32_t) alw * blw;
	 int32_t hl = ( int32_t) ahw * blw;
	return (ll >> FRACBITS) + hl;
}


//
// FixedReciprocalSmall
// Divide FFFFFFFFh by a 16-bit number.
//

#if defined C_ONLY
#define FixedReciprocalSmall(v) (0xffffffffu/(uint16_t)(v))
#define FixedReciprocalBig(v)   (0xffffffffu/(v))
#else
fixed_t  CONSTFUNC FixedReciprocalSmall(uint16_t v);
uint16_t CONSTFUNC FixedReciprocalBig(fixed_t v);
#endif


//Approx fixed point divide of a/b using reciprocal. -> a * (1/b).
#if defined __WATCOMC__
//
#else
inline
#endif
fixed_t CONSTFUNC FixedApproxDiv(fixed_t a, fixed_t b)
{
	if (b <= 0xffffu)
		return FixedMul3232(a, FixedReciprocalSmall(b));
	else
		return FixedMul3216(a, FixedReciprocalBig(b));
}


#if defined __WATCOMC__
//
#else
inline
#endif
fixed_t CONSTFUNC FixedApproxDiv3216(fixed_t a, uint16_t b)
{
	return FixedMul3232(a, FixedReciprocalSmall(b));
}


//
// R_PointOnSide
// Traverse BSP (sub) tree,
//  check point against partition plane.
// Returns side 0 (front) or 1 (back).
//

static PUREFUNC int16_t R_PointOnSide(fixed_t x, fixed_t y, const mapnode_t __far* node)
{
	int16_t ix = x >> FRACBITS;

	if (!node->dx)
		return ix <= node->x ? node->dy > 0 : node->dy < 0;

	int16_t iy = y >> FRACBITS;

	if (!node->dy)
		return iy <= node->y ? node->dx < 0 : node->dx > 0;

	x -= (fixed_t)node->x << FRACBITS;
	y -= (fixed_t)node->y << FRACBITS;

	ix = x >> FRACBITS;
	iy = y >> FRACBITS;

	// Try to quickly decide by looking at sign bits.
	if ((node->dy ^ node->dx ^ ix ^ iy) < 0)
		return (node->dy ^ ix) < 0;  // (left is negative)

	//return FixedMul(y, node->dx) >= FixedMul(x, node->dy);
	return (y >> 8) * node->dx >= (x >> 8) * node->dy;
}

//
// R_PointInSubsector
//

subsector_t __far* R_PointInSubsector(fixed_t x, fixed_t y)
{
    int16_t nodenum = numnodes-1;

    // special case for trivial maps (single subsector, no nodes)
    if (numnodes == 0)
        return _g_subsectors;

    while (!(nodenum & NF_SUBSECTOR))
        nodenum = nodes[nodenum].children[R_PointOnSide(x, y, nodes+nodenum)];
    return &_g_subsectors[(int16_t)(nodenum & ~NF_SUBSECTOR)];
}


#define SLOPERANGE 2048

static CONSTFUNC int16_t SlopeDiv(uint32_t num, uint32_t den)
{
    den = den >> 8;

    if (den == 0)
        return SLOPERANGE;

    const uint16_t ans = (num << 3) / den;//FixedApproxDiv(num << 3, den) >> FRACBITS;

    return (ans <= SLOPERANGE) ? ans : SLOPERANGE;
}


static CONSTFUNC int16_t SlopeDiv16(uint16_t n, uint16_t d)
{
	if (d == 0)
		return SLOPERANGE;

	const uint16_t ans = ((uint32_t)n * SLOPERANGE) / d;

	return (ans <= SLOPERANGE) ? ans : SLOPERANGE;
}


//
// R_PointToAngle
// To get a global angle from cartesian coordinates,
//  the coordinates are flipped until they are in
//  the first octant of the coordinate system, then
//  the y (<=x) is scaled and divided by x to get a
//  tangent (slope) value which is looked up in the
//  tantoangleTable[] table.
//


CONSTFUNC angle_t R_PointToAngle3(fixed_t x, fixed_t y)
{
    if ( (!x) && (!y) )
        return 0;

    if (x>= 0)
    {
        // x >=0
        if (y>= 0)
        {
            // y>= 0

            if (x>y)
            {
                // octant 0
                return tantoangle(SlopeDiv(y,x));
            }
            else
            {
                // octant 1
                return ANG90-1-tantoangle(SlopeDiv(x,y));
            }
        }
        else
        {
            // y<0
            y = -y;

            if (x>y)
            {
                // octant 8
                return -tantoangle(SlopeDiv(y,x));
            }
            else
            {
                // octant 7
                return ANG270+tantoangle(SlopeDiv(x,y));
            }
        }
    }
    else
    {
        // x<0
        x = -x;

        if (y>= 0)
        {
            // y>= 0
            if (x>y)
            {
                // octant 3
                return ANG180-1-tantoangle(SlopeDiv(y,x));
            }
            else
            {
                // octant 2
                return ANG90+ tantoangle(SlopeDiv(x,y));
            }
        }
        else
        {
            // y<0
            y = -y;

            if (x>y)
            {
                // octant 4
                return ANG180+tantoangle(SlopeDiv(y,x));
            }
            else
            {
                // octant 5
                return ANG270-1-tantoangle(SlopeDiv(x,y));
            }
        }
    }
}


#define R_PointToAngle(x,y) R_PointToAngle16((x)>>FRACBITS,(y)>>FRACBITS)


static angle16_t R_PointToAngle16(int16_t x, int16_t y)
{
    x = x - (viewx >> FRACBITS);
    y = y - (viewy >> FRACBITS);

    if (!x && !y)
        return 0;

    if (x >= 0)
    {
        // x >= 0
        if (y >= 0)
        {
            // y >= 0

            if (x > y)
            {
                // octant 0
                return tantoangle16(SlopeDiv16(y, x));
            }
            else
            {
                // octant 1
                return ANG90_16 - 1 - tantoangle16(SlopeDiv16(x, y));
            }
        }
        else
        {
            // y < 0
            y = -y;

            if (x > y)
            {
                // octant 8
                return -tantoangle16(SlopeDiv16(y, x));
            }
            else
            {
                // octant 7
                return ANG270_16 + tantoangle16(SlopeDiv16(x, y));
            }
        }
    }
    else
    {
        // x < 0
        x = -x;

        if (y >= 0)
        {
            // y >= 0
            if (x > y)
            {
                // octant 3
                return ANG180_16 - 1 - tantoangle16(SlopeDiv16(y, x));
            }
            else
            {
                // octant 2
                return ANG90_16 + tantoangle16(SlopeDiv16(x, y));
            }
        }
        else
        {
            // y < 0
            y = -y;

            if (x > y)
            {
                // octant 4
                return ANG180_16 + tantoangle16(SlopeDiv16(y, x));
            }
            else
            {
                // octant 5
                return ANG270_16 - 1 - tantoangle16(SlopeDiv16(x, y));
            }
        }
    }
}


#define SLOPEBITS    11
#define DBITS      (FRACBITS-SLOPEBITS)

static CONSTFUNC int16_t R_PointToDist(fixed_t x, fixed_t y)
{
    if (viewx == x && viewy == y)
        return 0;

    fixed_t dx = D_abs(x - viewx);
    fixed_t dy = D_abs(y - viewy);

    if (dy > dx)
    {
        fixed_t t = dx;
        dx = dy;
        dy = t;
    }

    return dx / finecosineapprox((FixedApproxDiv(dy,dx) >> DBITS) / 2);
}


// Lighting constants.

#define LIGHTSEGSHIFT      4


// Number of diminishing brightness levels.
// There a 0-31, i.e. 32 LUT in the COLORMAP lump.

#define NUMCOLORMAPS 32


const uint8_t __far* R_LoadColorMap(int16_t lightlevel)
{
    if (fixedcolormap)
        return fixedcolormap;
    else
    {
        if (curline)
        {
            if (curline->v1.y == curline->v2.y)
                lightlevel -= 1 << LIGHTSEGSHIFT;
            else if (curline->v1.x == curline->v2.x)
                lightlevel += 1 << LIGHTSEGSHIFT;
        }

        lightlevel += (extralight +_g_gamma) << LIGHTSEGSHIFT;

        int16_t cm = ((256-lightlevel)>>2) - 24;

        if(cm >= NUMCOLORMAPS)
            cm = NUMCOLORMAPS-1;
        else if(cm < 0)
            cm = 0;

        return fullcolormap + cm*256;
    }
}


//
// R_DrawMaskedColumn
// Used for sprites and masked mid textures.
// Masked means: partly transparent, i.e. stored
//  in posts/runs of opaque pixels.
//

typedef void (*R_DrawColumn_f)(const draw_column_vars_t *dcvars);

static void R_DrawMaskedColumn(R_DrawColumn_f colfunc, draw_column_vars_t *dcvars, const column_t __far* column)
{
    const fixed_t basetexturemid = dcvars->texturemid;

    const int16_t fclip_x = mfloorclip[dcvars->x];
    const int16_t cclip_x = mceilingclip[dcvars->x];

    while (column->topdelta != 0xff)
    {
        // calculate unclipped screen coordinates for post
        const int32_t topscreen = sprtopscreen + spryscale*column->topdelta;
        const int32_t bottomscreen = topscreen + spryscale*column->length;

        int16_t yh = (bottomscreen-1)>>FRACBITS;
        int16_t yl = (topscreen+FRACUNIT-1)>>FRACBITS;

        if (yh >= fclip_x)
            yh = fclip_x - 1;

        if (yl <= cclip_x)
            yl = cclip_x + 1;

        // killough 3/2/98, 3/27/98: Failsafe against overflow/crash:
        if (yl <= yh && yh < VIEWWINDOWHEIGHT)
        {
            dcvars->source =  (const byte __far*)column + 3;

            dcvars->texturemid = basetexturemid - (((int32_t)column->topdelta)<<FRACBITS);

            dcvars->yh = yh;
            dcvars->yl = yl;

            // Drawn by either R_DrawColumn or (SHADOW) R_DrawFuzzColumn.
            colfunc (dcvars);
        }

        column = (const column_t __far*)((const byte __far*)column + column->length + 4);
    }

    dcvars->texturemid = basetexturemid;
}


//
// R_InitColormaps
//
void R_InitColormaps(void)
{
	fullcolormap = W_GetLumpByName("COLORMAP"); // Never freed
}


//
// A vissprite_t is a thing that will be drawn during a refresh.
// i.e. a sprite object that is partly visible.
//

typedef struct vissprite_s
{
  int16_t x1, x2;
  fixed_t gx, gy;              // for line side calculation
  fixed_t gz;                   // global bottom for silhouette clipping
  fixed_t startfrac;           // horizontal position of x1
  fixed_t scale;
  fixed_t xiscale;             // negative if flipped
  fixed_t texturemid;
  fixed_t iscale;

  int16_t lump_num;
  int16_t patch_topoffset;

  // for color translation and shadow draw, maxbright frames as well
  const uint8_t __far* colormap;

} vissprite_t;


void R_DrawFuzzColumn (const draw_column_vars_t *dcvars);


//
// R_DrawVisSprite
//  mfloorclip and mceilingclip should also be set.
//
// CPhipps - new wad lump handling, *'s to const*'s
static void R_DrawVisSprite(const vissprite_t *vis)
{
    fixed_t  frac;

    R_DrawColumn_f colfunc = R_DrawColumn;
    draw_column_vars_t dcvars;
    dcvars.colormap = vis->colormap;

    // killough 4/11/98: rearrange and handle translucent sprites
    // mixed with translucent/non-translucenct 2s normals

    if (!dcvars.colormap)   // NULL colormap = shadow draw
        colfunc = R_DrawFuzzColumn;    // killough 3/14/98

    // proff 11/06/98: Changed for high-res
    dcvars.iscale = vis->iscale;
    dcvars.texturemid = vis->texturemid;
    frac = vis->startfrac;

    spryscale = vis->scale;
    sprtopscreen = CENTERY * FRACUNIT - FixedMul(dcvars.texturemid, spryscale);


    const patch_t __far* patch = W_GetLumpByNum(vis->lump_num);

    dcvars.x = vis->x1;

    while (dcvars.x < VIEWWINDOWWIDTH)
    {
        const column_t __far* column = (const column_t __far*) ((const byte __far*)patch + (uint16_t)patch->columnofs[frac >> FRACBITS]);
        R_DrawMaskedColumn(colfunc, &dcvars, column);

        frac += vis->xiscale;

        if(((frac >> FRACBITS) >= patch->width) || frac < 0)
            break;

        dcvars.x++;
    }

    Z_ChangeTagToCache(patch);
}


static void R_GetColumn(const texture_t __far* texture, int16_t texcolumn, int16_t* patch_num, int16_t* x_c)
{
    const uint8_t patchcount = texture->patchcount;
    const uint16_t widthmask = texture->widthmask;

    const int16_t xc = texcolumn & widthmask;

    if (patchcount != 1)
    {
        uint8_t i = 0;

        do
        {
            const texpatch_t __far* patch = &texture->patches[i];

            const int16_t x1 = patch->originx;

            if (xc < x1)
                continue;

            const int16_t x2 = x1 + patch->patch_width;

            if (xc < x2)
            {
                *patch_num = patch->patch_num;
                *x_c = xc - x1;
                return;
            }
        } while (++i < patchcount);

        printf("R_GetColumn: can't find texcolumn\n");
    }

    //patchcount == 1
    //simple texture.
    *patch_num = texture->patches[0].patch_num;
    *x_c = xc;
}


//
// R_RenderMaskedSegRange
//

static void R_RenderMaskedSegRange(const drawseg_t *ds, int16_t x1, int16_t x2)
{
    int16_t      texnum;
    draw_column_vars_t dcvars;

    // Calculate light table.
    // Use different light tables
    //   for horizontal / vertical / diagonal. Diagonal?

    curline = ds->curline;  // OPTIMIZE: get rid of LIGHTSEGSHIFT globally

    frontsector = &_g_sectors[curline->frontsectornum];
    backsector  = &_g_sectors[curline->backsectornum];

    texnum = _g_sides[curline->sidenum].midtexture;
    texnum = texturetranslation[texnum];

    // killough 4/13/98: get correct lightlevel for 2s normal textures
    rw_lightlevel = frontsector->lightlevel;

    maskedtexturecol = ds->maskedtexturecol;

    rw_scalestep = ds->scalestep;
    spryscale    = ds->scale1 + (x1 - ds->x1) * rw_scalestep;
    mfloorclip   = ds->sprbottomclip;
    mceilingclip = ds->sprtopclip;

    // find positioning
    if (_g_lines[curline->linenum].flags & ML_DONTPEGBOTTOM)
    {
        dcvars.texturemid = frontsector->floorheight > backsector->floorheight
                ? frontsector->floorheight : backsector->floorheight;
        dcvars.texturemid = dcvars.texturemid + ((int32_t)textureheight[texnum] << FRACBITS) - viewz;
    }
    else
    {
        dcvars.texturemid =frontsector->ceilingheight<backsector->ceilingheight
                ? frontsector->ceilingheight : backsector->ceilingheight;
        dcvars.texturemid = dcvars.texturemid - viewz;
    }

    dcvars.texturemid += (((int32_t)_g_sides[curline->sidenum].rowoffset) << FRACBITS);

    const texture_t __far* texture = R_GetTexture(texnum);

    dcvars.colormap = R_LoadColorMap(rw_lightlevel);

    // draw the columns
    for (dcvars.x = x1 ; dcvars.x <= x2 ; dcvars.x++, spryscale += rw_scalestep)
    {
        int16_t xc = maskedtexturecol[dcvars.x];

        if (xc != SHRT_MAX) // dropoff overflow
        {
            sprtopscreen = CENTERY * FRACUNIT - FixedMul(dcvars.texturemid, spryscale);

            dcvars.iscale = FixedReciprocal((uint32_t)spryscale);

            // draw the texture
            int16_t patch_num;
            int16_t x_c;
            R_GetColumn(texture, xc, &patch_num, &x_c);
            const patch_t __far* patch = W_GetLumpByNum(patch_num);
            const column_t __far* column = (const column_t __far*) ((const byte __far*)patch + (uint16_t)patch->columnofs[x_c]);

            R_DrawMaskedColumn(R_DrawColumn, &dcvars, column);
            Z_ChangeTagToCache(patch);
            maskedtexturecol[dcvars.x] = SHRT_MAX; // dropoff overflow
        }
    }

    curline = NULL; /* cph 2001/11/18 - must clear curline now we're done with it, so R_LoadColorMap doesn't try using it for other things */
}


static PUREFUNC boolean R_PointOnSegSide(fixed_t x, fixed_t y, const seg_t __far* line)
{
    const fixed_t lx = line->v1.x;
    const fixed_t ly = line->v1.y;
    const fixed_t ldx = line->v2.x - lx;
    const fixed_t ldy = line->v2.y - ly;

    if (!ldx)
        return x <= lx ? ldy > 0 : ldy < 0;

    if (!ldy)
        return y <= ly ? ldx < 0 : ldx > 0;

    x -= lx;
    y -= ly;

    // Try to quickly decide by looking at sign bits.
    if ((ldy ^ ldx ^ x ^ y) < 0)
        return (ldy ^ x) < 0;          // (left is negative)

    return FixedMul3216(y, ldx>>FRACBITS) >= FixedMul3216(x, ldy>>FRACBITS);
}


//
// R_DrawSprite
//

static void R_DrawSprite (const vissprite_t* spr)
{
    int16_t* clipbot = floorclip;
    int16_t* cliptop = ceilingclip;

    fixed_t scale;
    fixed_t lowscale;

    for (int16_t x = spr->x1; x <= spr->x2; x++)
    {
        clipbot[x] = VIEWWINDOWHEIGHT;
        cliptop[x] = -1;
    }


    // Scan drawsegs from end to start for obscuring segs.
    // The first drawseg that has a greater scale is the clip seg.

    // Modified by Lee Killough:
    // (pointer check was originally nonportable
    // and buggy, by going past LEFT end of array):

    const drawseg_t* drawsegs  =_s_drawsegs;

    for (const drawseg_t* ds = ds_p; ds-- > drawsegs; )  // new -- killough
    {
        // determine if the drawseg obscures the sprite
        if (ds->x1 > spr->x2 || ds->x2 < spr->x1 || (!ds->silhouette && !ds->maskedtexturecol))
            continue;      // does not cover sprite

        const int16_t r1 = ds->x1 < spr->x1 ? spr->x1 : ds->x1;
        const int16_t r2 = ds->x2 > spr->x2 ? spr->x2 : ds->x2;

        if (ds->scale1 > ds->scale2)
        {
            lowscale = ds->scale2;
            scale    = ds->scale1;
        }
        else
        {
            lowscale = ds->scale1;
            scale    = ds->scale2;
        }

        if (scale < spr->scale || (lowscale < spr->scale && !R_PointOnSegSide (spr->gx, spr->gy, ds->curline)))
        {
            if (ds->maskedtexturecol)       // masked mid texture?
                R_RenderMaskedSegRange(ds, r1, r2);

            continue;               // seg is behind sprite
        }

        // clip this piece of the sprite
        // killough 3/27/98: optimized and made much shorter

        if (ds->silhouette & SIL_BOTTOM && spr->gz < ds->bsilheight) //bottom sil
        {
            for (int16_t x = r1; x <= r2; x++)
            {
                if (clipbot[x] == VIEWWINDOWHEIGHT)
                    clipbot[x] = ds->sprbottomclip[x];
            }
        }

        fixed_t gzt = spr->gz + (((int32_t)spr->patch_topoffset) << FRACBITS);

        if (ds->silhouette & SIL_TOP && gzt > ds->tsilheight)   // top sil
        {
            for (int16_t x = r1; x <= r2; x++)
            {
                if (cliptop[x] == -1)
                    cliptop[x] = ds->sprtopclip[x];
            }
        }
    }

    // all clipping has been performed, so draw the sprite
    mfloorclip   = clipbot;
    mceilingclip = cliptop;
    R_DrawVisSprite (spr);
}


/*
 * Frame flags:
 * handles maximum brightness (torches, muzzle flare, light sources)
 */

#define FF_FULLBRIGHT   0x8000  /* flag in thing->frame */
#define FF_FRAMEMASK    0x7fff


//
// R_DrawPSprite
//

#define BASEXCENTER (SCREENWIDTH_VGA  / 2)
#define BASEYCENTER (SCREENHEIGHT_VGA / 2L)

static void R_DrawPSprite (pspdef_t *psp, int16_t lightlevel)
{
    int16_t           x1, x2;
    uint32_t hl;
    spritedef_t   __far* sprdef;
    spriteframe_t __far* sprframe;
    vissprite_t   *vis;
    vissprite_t   avis;
    fixed_t       topoffset;

    // decide which patch to use
    sprdef = &sprites[psp->state->sprite];

    sprframe = &sprdef->spriteframes[psp->state->frame & FF_FRAMEMASK];

    const patch_t __far* patch = W_GetLumpByNum(sprframe->lump[0]);
    // calculate edges of the shape
    int16_t tx = psp->sx - BASEXCENTER;

    tx -= patch->leftoffset;
    hl = (uint32_t) tx * PSPRITESCALE;
    x1 = CENTERX + (hl >> FRACBITS);

    tx += patch->width;
    hl = (uint32_t) tx * PSPRITESCALE;
    x2 = CENTERX + (hl >> FRACBITS) - 1;

    // off the side
    if (x2 < 0 || x1 > VIEWWINDOWWIDTH)
    {
        Z_ChangeTagToCache(patch);
        return;
    }

    topoffset = ((int32_t)patch->topoffset) << FRACBITS;
    Z_ChangeTagToCache(patch);

    // store information in a vissprite
    vis = &avis;
    // killough 12/98: fix psprite positioning problem
    vis->texturemid = (BASEYCENTER<<FRACBITS) /* +  FRACUNIT/2 */ -
            (psp->sy-topoffset);
    vis->x1 = x1 < 0 ? 0 : x1;
    vis->x2 = x2 >= VIEWWINDOWWIDTH ? VIEWWINDOWWIDTH - 1 : x2;
    // proff 11/06/98: Added for high-res
    vis->scale = PSPRITEYSCALE;
    vis->iscale = PSPRITEYISCALE;

    vis->xiscale = PSPRITEISCALE;
    vis->startfrac = 0;

    if (vis->x1 > x1)
        vis->startfrac = vis->xiscale*(vis->x1-x1);

    vis->lump_num = sprframe->lump[0];

    if (_g_player.powers[pw_invisibility] > 4*32 || _g_player.powers[pw_invisibility] & 8)
        vis->colormap = NULL;                    // shadow draw
    else if (fixedcolormap)
        vis->colormap = fixedcolormap;           // fixed color
    else if (psp->state->frame & FF_FULLBRIGHT)
        vis->colormap = fullcolormap;            // full bright // killough 3/20/98
    else
        vis->colormap = R_LoadColorMap(lightlevel);  // local light

    R_DrawVisSprite(vis);
}



//
// R_DrawPlayerSprites
//

static void R_DrawPlayerSprites(void)
{

  int16_t i, lightlevel = _g_player.mo->subsector->sector->lightlevel;
  pspdef_t *psp;

  // clip to screen bounds
  mfloorclip   = screenheightarray;
  mceilingclip = negonearray;

  // add all active psprites
  for (i=0, psp=_g_player.psprites; i<NUMPSPRITES; i++,psp++)
    if (psp->state)
      R_DrawPSprite (psp, lightlevel);
}


//
// R_SortVisSprites
//
static int compare (const void* l, const void* r)
{
	const vissprite_t* vl = *(const vissprite_t**)l;
	const vissprite_t* vr = *(const vissprite_t**)r;

	fixed_t diff = vr->scale - vl->scale;
	if (!diff)
		return 0;
	else if (diff < 0)
		return -1;
	else
		return 1;
}

#define MAXVISSPRITES 96
static int8_t num_vissprite;
static vissprite_t vissprites[MAXVISSPRITES];
static vissprite_t* vissprite_ptrs[MAXVISSPRITES];

static void R_SortVisSprites (void)
{
    int8_t i = num_vissprite;

    if (i)
    {
        while (--i >= 0)
            vissprite_ptrs[i] = vissprites + i;

        qsort(vissprite_ptrs, num_vissprite, sizeof (vissprite_t*), compare);
    }
}

//
// R_DrawMasked
//

static void R_DrawMasked(void)
{
    drawseg_t *ds;
    drawseg_t* drawsegs = _s_drawsegs;


    R_SortVisSprites();

    // draw all vissprites back to front
    for (int8_t i = num_vissprite; --i >= 0; )
        R_DrawSprite(vissprite_ptrs[i]);

    // render any remaining masked mid textures

    for (ds=ds_p ; ds-- > drawsegs ; )
        if (ds->maskedtexturecol)
            R_RenderMaskedSegRange(ds, ds->x1, ds->x2);

    R_DrawPlayerSprites ();
}


//
// R_NewVisSprite
//
static vissprite_t *R_NewVisSprite(void)
{
    if (num_vissprite >= MAXVISSPRITES)
    {
#ifdef RANGECHECK
        I_Error("Vissprite overflow.");
#endif
        return NULL;
    }

    return vissprites + num_vissprite++;
}


//
// R_ClearSprites
// Called at frame start.
//

static void R_ClearSprites(void)
{
    num_vissprite = 0;
}


//*******************************************

//
// R_ScaleFromGlobalAngle
// Returns the texture mapping scale
//  for the current line (horizontal span)
//  at the given angle.
// rw_distance must be calculated first.
//

static fixed_t R_ScaleFromGlobalAngle(int16_t x)
{
  int16_t anglea = ANG90_16 + xtoviewangleTable[x];
  int16_t angleb = anglea + viewangle16 - rw_normalangle;

  fixed_t den = rw_distance * finesineapprox(anglea >> ANGLETOFINESHIFT_16);

// proff 11/06/98: Changed for high-res
  fixed_t num = VIEWWINDOWHEIGHT * finesineapprox(angleb >> ANGLETOFINESHIFT_16);

  return den > num>>16 ? (num = FixedApproxDiv(num, den)) > 64*FRACUNIT ?
    64*FRACUNIT : num < 256 ? 256 : num : 64*FRACUNIT;
}


//
// R_ProjectSprite
// Generates a vissprite for a thing if it might be visible.
//

#define MINZ        (FRACUNIT*4)
#define MAXZ        (FRACUNIT*1280)

#define SPR_FLIPPED(s, r) (s->flipmask & (1 << r))

static void R_ProjectSprite (mobj_t __far* thing, int16_t lightlevel)
{
    const fixed_t fx = thing->x;
    const fixed_t fy = thing->y;
    const fixed_t fz = thing->z;

    const fixed_t tr_x = fx - viewx;
    const fixed_t tr_y = fy - viewy;

    fixed_t xc = FixedMulAngle(tr_x, viewcos);
    fixed_t ys = FixedMulAngle(tr_y, viewsin);
    const fixed_t tz = xc - (-ys);

    // thing is behind view plane?
    if (tz < MINZ)
        return;

    //Too far away.
    if(tz > MAXZ)
        return;

    fixed_t yc = FixedMulAngle(tr_y, viewcos);
    fixed_t xs = FixedMulAngle(tr_x, viewsin);
    fixed_t tx = -(yc + (-xs));

    // too far off the side?
    if (D_abs(tx)>(tz<<2))
        return;

    // decide which patch to use for sprite relative to player
    const spritedef_t __far*   sprdef   = &sprites[thing->sprite];
    const spriteframe_t __far* sprframe = &sprdef->spriteframes[thing->frame & FF_FRAMEMASK];

    uint16_t rot = 0;

    if (sprframe->rotate)
    {
        // choose a different rotation based on player view
        angle16_t ang = R_PointToAngle(fx, fy);
        rot = (angle16_t)(ang - (angle16_t)(thing->angle >> FRACBITS) + (angle16_t)(ANG45_16 / 2) * 9) >> 13;
    }

    const boolean flip = (boolean)SPR_FLIPPED(sprframe, rot);
    const patch_t __far* patch = W_GetLumpByNum(sprframe->lump[rot]);

    /* calculate edges of the shape
     * cph 2003/08/1 - fraggle points out that this offset must be flipped
     * if the sprite is flipped; e.g. FreeDoom imp is messed up by this. */
    if (flip)
        tx -= ((int32_t)(patch->width - patch->leftoffset)) << FRACBITS;
    else
        tx -= ((int32_t)patch->leftoffset) << FRACBITS;

    //const fixed_t xscale = FixedDiv(PROJECTION, tz);
    const fixed_t xscale = PROJECTION / (tz >> FRACBITS);

    fixed_t xl = CENTERX * FRACUNIT + FixedMul(tx,xscale);
    const int16_t x1 = (xl >> FRACBITS);

    // off the side?
    if (x1 > VIEWWINDOWWIDTH)
    {
        Z_ChangeTagToCache(patch);
        return;
    }

    fixed_t xr = CENTERX * FRACUNIT + FixedMul(tx + (((int32_t)patch->width) << FRACBITS), xscale) - FRACUNIT;
    const int16_t x2 = (xr >> FRACBITS);

    // off the side?
    if (xr < 0)
    {
        Z_ChangeTagToCache(patch);
        return;
    }

    //Too small.
    if (xr <= (xl + (FRACUNIT >> 2)))
    {
        Z_ChangeTagToCache(patch);
        return;
    }


    // store information in a vissprite
    vissprite_t* vis = R_NewVisSprite ();

    //No more vissprites.
    if(!vis)
    {
        Z_ChangeTagToCache(patch);
        return;
    }

    //vis->scale           = FixedDiv(PROJECTIONY, tz);
    vis->scale           = (VIEWWINDOWHEIGHT * FRACUNIT) / (tz >> FRACBITS);
    vis->iscale          = tz / VIEWWINDOWHEIGHT;
    vis->lump_num        = sprframe->lump[rot];
    vis->patch_topoffset = patch->topoffset;
    vis->gx              = fx;
    vis->gy              = fy;
    vis->gz              = fz;
    vis->texturemid      = (fz + (((int32_t)patch->topoffset) << FRACBITS)) - viewz;
    vis->x1              = x1 < 0 ? 0 : x1;
    vis->x2              = x2 >= VIEWWINDOWWIDTH ? VIEWWINDOWWIDTH - 1 : x2;


    const fixed_t iscale = FixedReciprocal(xscale);

    if (flip)
    {
        vis->startfrac = (((int32_t)patch->width)<<FRACBITS)-1;
        vis->xiscale = -iscale;
    }
    else
    {
        vis->startfrac = 0;
        vis->xiscale = iscale;
    }

    Z_ChangeTagToCache(patch);

    if (vis->x1 > x1)
        vis->startfrac += vis->xiscale*(vis->x1-x1);

    // get light level
    if (thing->flags & MF_SHADOW)
        vis->colormap = NULL;             // shadow draw
    else if (fixedcolormap)
        vis->colormap = fixedcolormap;      // fixed map
    else if (thing->frame & FF_FULLBRIGHT)
        vis->colormap = fullcolormap;     // full bright  // killough 3/20/98
    else
        vis->colormap = R_LoadColorMap(lightlevel); // diminished light
}

//
// R_AddSprites
// During BSP traversal, this adds sprites by sector.
//
// killough 9/18/98: add lightlevel as parameter, fixing underwater lighting
static void R_AddSprites(subsector_t __far* subsec, int16_t lightlevel)
{
  sector_t __far* sec=subsec->sector;
  mobj_t __far* thing;

  // BSP is traversed by subsector.
  // A sector might have been split into several
  //  subsectors during BSP building.
  // Thus we check whether its already added.

  if (sec->validcount == validcount)
    return;

  // Well, now it will be done.
  sec->validcount = validcount;

  // Handle all things in sector.

  for (thing = sec->thinglist; thing; thing = thing->snext)
    R_ProjectSprite(thing, lightlevel);
}


#if defined FLAT_WALL
#define R_DrawSegTextureColumn(x,y,z) R_DrawColumnFlat(x,z)
#else
static void R_DrawColumnInCache(const column_t __far* patch, byte* cache, int16_t originy, int16_t cacheheight)
{
    while (patch->topdelta != 0xff)
    {
        const byte __far* source = (const byte __far*)patch + 3;
        int16_t count = patch->length;
        int16_t position = originy + patch->topdelta;

        if (position < 0)
        {
            count += position;
            position = 0;
        }

        if (position + count > cacheheight)
            count = cacheheight - position;

        if (count > 0)
            _fmemcpy(cache + position, source, count);

        patch = (const column_t __far*)((const byte __far*)patch + patch->length + 4);
    }
}

/*
 * Draw a column of pixels of the specified texture.
 * If the texture is simple (1 patch, full height) then just draw
 * straight from const patch_t*.
*/

#define CACHE_WAYS 4

#define CACHE_MASK (CACHE_WAYS-1)
#define CACHE_STRIDE (128 / CACHE_WAYS)
#define CACHE_KEY_MASK (CACHE_STRIDE-1)

static uint16_t CACHE_ENTRY(int16_t column, int16_t texture)
{
	return column | (texture << 8);
}

static uint16_t CACHE_HASH(int16_t column, int16_t texture)
{
	return ((column >> 1) ^ texture) & CACHE_KEY_MASK;
}

static byte __far columnCache[128*128];
static uint16_t columnCacheEntries[128];

static uint16_t FindColumnCacheItem(int16_t texture, int16_t column)
{
    uint16_t cx = CACHE_ENTRY(column, texture);

    uint16_t key = CACHE_HASH(column, texture);

    uint16_t* cc = &columnCacheEntries[key];

    uint16_t i = key;

    do
    {
        uint16_t cy = *cc;

        if((cy == cx) || (cy == 0))
            return i;

        cc+=CACHE_STRIDE;
        i+=CACHE_STRIDE;

    } while(i < 128);


    //No space. Random eviction.
    return ((M_Random() & CACHE_MASK) * CACHE_STRIDE) + key;
}


static const byte __far* R_ComposeColumn(const int16_t texture, const texture_t __far* tex, int16_t texcolumn, uint16_t iscale)
{
    uint16_t colmask = 0xfffe;

    if (tex->width > 8)
    {
        if (iscale > 4)
            colmask = 0xfff0;
        else if (iscale > 3)
            colmask = 0xfff8;
        else if (iscale > 2)
            colmask = 0xfffc;
    }


    const int16_t xc = (texcolumn & colmask) & tex->widthmask;

    uint16_t cachekey = FindColumnCacheItem(texture, xc);

    byte __far* colcache = &columnCache[cachekey*128];
    uint16_t cacheEntry = columnCacheEntries[cachekey];

    //total++;

    if (cacheEntry != CACHE_ENTRY(xc, texture))
    {
        //misses++;
        byte tmpCache[128];

        uint8_t i = 0;
        uint8_t patchcount = tex->patchcount;

        do
        {
            const texpatch_t __far* patch = &tex->patches[i];

            const int16_t x1 = patch->originx;

            if (xc < x1)
                continue;

            const patch_t __far* realpatch = W_TryGetLumpByNum(patch->patch_num);
            if (realpatch == NULL)
                return NULL;

            const int16_t x2 = x1 + realpatch->width;

            if (xc < x2)
            {
                const column_t __far* patchcol = (const column_t __far*)((const byte __far*)realpatch + (uint16_t)realpatch->columnofs[xc - x1]);

                R_DrawColumnInCache (patchcol, tmpCache, patch->originy, tex->height);
            }
            Z_ChangeTagToCache(realpatch);
        } while(++i < patchcount);

        //Block copy will drop low 2 bits of len.
        _fmemcpy(colcache, tmpCache, (tex->height + 3) & ~3);

        columnCacheEntries[cachekey] = CACHE_ENTRY(xc, texture);
    }

    return colcache;
}

static void R_DrawSegTextureColumn(int16_t texture, int16_t texcolumn, draw_column_vars_t* dcvars)
{
    const texture_t __far* tex = R_GetTexture(texture);

    if (!tex->overlapped)
    {
        int16_t patch_num;
        int16_t x_c;
        R_GetColumn(tex, texcolumn, &patch_num, &x_c);

        const patch_t __far* patch = W_TryGetLumpByNum(patch_num);
        if (patch == NULL)
            R_DrawColumnFlat(texture, dcvars);
        else
        {
            const column_t __far* column = (const column_t __far*) ((const byte __far*)patch + (uint16_t)patch->columnofs[x_c]);

            dcvars->source = (const byte __far*)column + 3;
            R_DrawColumn (dcvars);
            Z_ChangeTagToCache(patch);
        }
    }
    else
    {
        const byte __far* source = R_ComposeColumn(texture, tex, texcolumn, dcvars->iscale >> FRACBITS);
        if (source == NULL)
            R_DrawColumnFlat(texture, dcvars);
        else
        {
            dcvars->source = source;
            R_DrawColumn (dcvars);
        }
    }
}
#endif

//
// R_RenderSegLoop
// Draws zero, one, or two textures (and possibly a masked texture) for walls.
// Can draw or mark the starting pixel of floor and ceiling textures.
// boolean segtextured is true if any of the segs textures might be visible.
// boolean markfloor is false if the back side is the same plane.
// CALLED: CORE LOOPING ROUTINE.
//

#define HEIGHTBITS 12
#define HEIGHTUNIT (1<<HEIGHTBITS)

static void R_RenderSegLoop(int16_t rw_x, boolean segtextured, boolean markfloor, boolean markceiling)
{
    draw_column_vars_t dcvars;
    int16_t  texturecolumn = 0;   // shut up compiler warning

    dcvars.colormap = R_LoadColorMap(rw_lightlevel);

    for ( ; rw_x < rw_stopx ; rw_x++)
    {
        // mark floor / ceiling areas

        int16_t yh = bottomfrac>>HEIGHTBITS;
        int16_t yl = (topfrac+HEIGHTUNIT-1)>>HEIGHTBITS;

        int16_t cc_rwx = ceilingclip[rw_x];
        int16_t fc_rwx = floorclip[rw_x];

        // no space above wall?
        int16_t bottom,top = cc_rwx+1;

        dcvars.x  = rw_x;

        if (yl < top)
            yl = top;

        if (markceiling)
        {
            bottom = yl-1;

            if (bottom >= fc_rwx)
                bottom = fc_rwx-1;

            if (top <= bottom)
            {
#if defined FLAT_SPAN
                dcvars.yl = top;
                dcvars.yh = bottom;
                if (ceilingplane_color == -2)
                    R_DrawSky(&dcvars);
                else
                    R_DrawColumnFlat(ceilingplane_color, &dcvars);
#else
                ceilingplane->top[rw_x] = top;
                ceilingplane->bottom[rw_x] = bottom;
                ceilingplane->modified = true;
#endif
            }
            // SoM: this should be set here
            cc_rwx = bottom;
        }

        bottom = fc_rwx-1;
        if (yh > bottom)
            yh = bottom;

        if (markfloor)
        {

            top  = yh < cc_rwx ? cc_rwx : yh;

            if (++top <= bottom)
            {
#if defined FLAT_SPAN
                dcvars.yl = top;
                dcvars.yh = bottom;
                R_DrawColumnFlat(floorplane_color, &dcvars);
#else
                floorplane->top[rw_x] = top;
                floorplane->bottom[rw_x] = bottom;
                floorplane->modified = true;
#endif
            }
            // SoM: This should be set here to prevent overdraw
            fc_rwx = top;
        }

        // texturecolumn and lighting are independent of wall tiers
        if (segtextured)
        {
            // calculate texture offset
#if !defined FLAT_WALL
			texturecolumn = rw_offset;
			int16_t ang = (angle16_t)(rw_centerangle + xtoviewangleTable[rw_x]) >> ANGLETOFINESHIFT_16;
			if (ang < 1024) {			//    0 <= ang < 1024
				fixed_t tan = finetangentTable_part_4[1023 - ang];
				texturecolumn += (rw_distance * tan) >> FRACBITS;
			} else if (ang < 2048) {	// 1024 <= ang < 2048
				fixed_t tan = finetangentTable_part_3[1023 - (ang - 1024)];
				texturecolumn += (rw_distance * tan) >> FRACBITS;
			} else if (ang < 3072) {	// 2048 <= ang < 3072
				fixed_t tan = finetangentTable_part_3[ang - 2048];
				texturecolumn -= (rw_distance * tan) >> FRACBITS;
			} else {					// 3072 <= ang < 4096
				fixed_t tan = finetangentTable_part_4[ang - 3072];
				texturecolumn -= (rw_distance * tan) >> FRACBITS;
			}
#endif

            dcvars.iscale = FixedReciprocal((uint32_t)rw_scale);
        }

        // draw the wall tiers
        if (midtexture)
        {

            dcvars.yl = yl;     // single sided line
            dcvars.yh = yh;
            dcvars.texturemid = rw_midtexturemid;
            //

            R_DrawSegTextureColumn(midtexture, texturecolumn, &dcvars);

            cc_rwx = VIEWWINDOWHEIGHT;
            fc_rwx = -1;
        }
        else
        {

            // two sided line
            if (toptexture)
            {
                // top wall
                int16_t mid = pixhigh>>HEIGHTBITS;
                pixhigh += pixhighstep;

                if (mid >= fc_rwx)
                    mid = fc_rwx-1;

                if (mid >= yl)
                {
                    dcvars.yl = yl;
                    dcvars.yh = mid;
                    dcvars.texturemid = rw_toptexturemid;

                    R_DrawSegTextureColumn(toptexture, texturecolumn, &dcvars);

                    cc_rwx = mid;
                }
                else
                    cc_rwx = yl-1;
            }
            else  // no top wall
            {

                if (markceiling)
                    cc_rwx = yl-1;
            }

            if (bottomtexture)          // bottom wall
            {
                int16_t mid = (pixlow+HEIGHTUNIT-1)>>HEIGHTBITS;
                pixlow += pixlowstep;

                // no space above wall?
                if (mid <= cc_rwx)
                    mid = cc_rwx+1;

                if (mid <= yh)
                {
                    dcvars.yl = mid;
                    dcvars.yh = yh;
                    dcvars.texturemid = rw_bottomtexturemid;

                    R_DrawSegTextureColumn(bottomtexture, texturecolumn, &dcvars);

                    fc_rwx = mid;
                }
                else
                    fc_rwx = yh+1;
            }
            else        // no bottom wall
            {
                if (markfloor)
                    fc_rwx = yh+1;
            }

            // cph - if we completely blocked further sight through this column,
            // add this info to the solid columns array for r_bsp.c
            if ((markceiling || markfloor) && (fc_rwx <= cc_rwx + 1))
            {
                solidcol[rw_x] = 1;
                didsolidcol = true;
            }

            // save texturecol for backdrawing of masked mid texture
            if (maskedtexture)
                maskedtexturecol[rw_x] = texturecolumn;
        }

        rw_scale += rw_scalestep;
        topfrac += topstep;
        bottomfrac += bottomstep;

        floorclip[rw_x] = fc_rwx;
        ceilingclip[rw_x] = cc_rwx;
    }
}

static boolean R_CheckOpenings(const int16_t start)
{
    int16_t pos = lastopening - openings;
    int16_t need = (rw_stopx - start)*sizeof(int16_t) + pos;

#ifdef RANGECHECK
    if(need > MAXOPENINGS)
        I_Error("Openings overflow. Need = %ld", need);
#endif

    return need <= MAXOPENINGS;
}


static void R_ClearOpeningClippingDetermination(void)
{
	// opening / clipping determination
	for (int8_t i = 0; i < VIEWWINDOWWIDTH; i++)
		floorclip[i] = VIEWWINDOWHEIGHT, ceilingclip[i] = -1;
}


static void R_ClearOpenings(void)
{
	lastopening = openings;
}


/* CPhipps -
 * Mod - returns a % b, guaranteeing 0 <= a < b
 * (notice that the C standard for % does not guarantee this)
 */

inline static int16_t CONSTFUNC Mod(int16_t a, int16_t b)
{
    if(!a)
        return 0;

    if (b & (b-1))
    {
        int16_t r = a % b;
        return ((r<0) ? r+b : r);
    }
    else
        return (a & (b-1));
}


//
// R_StoreWallRange
// A wall segment will be drawn
//  between start and stop pixels (inclusive).
//
static void R_StoreWallRange(const int16_t start, const int16_t stop)
{
    // don't overflow and crash
    if (ds_p == &_s_drawsegs[MAXDRAWSEGS])
    {
#ifdef RANGECHECK
        I_Error("Drawsegs overflow.");
#endif
        return;
    }


    linedata_t __far* linedata = &_g_linedata[curline->linenum];

    // mark the segment as visible for auto map
    linedata->r_flags |= ML_MAPPED;

    sidedef = &_g_sides[curline->sidenum];
    linedef = &_g_lines[curline->linenum];

    // calculate rw_distance for scale calculation
    rw_normalangle = (curline->angle >> FRACBITS) + ANG90_16;

    angle16_t offsetangle = rw_normalangle - rw_angle1;

#if defined _M_I86
    if (abs(offsetangle) > ANG90_16)
        offsetangle = ANG90_16;
#else
    if (D_abs((angle_t)offsetangle << FRACBITS) > ANG90)
        offsetangle = ANG90_16;
#endif

    int16_t hyp = R_PointToDist(curline->v1.x, curline->v1.y);

    rw_distance = (hyp * finecosineapprox(offsetangle >> ANGLETOFINESHIFT_16)) >> FRACBITS;

    int16_t rw_x = ds_p->x1 = start;
    ds_p->x2 = stop;
    ds_p->curline = curline;
    rw_stopx = stop+1;

    //Openings overflow. Nevermind.
    if(!R_CheckOpenings(start))
        return;

    // calculate scale at both ends and step
    ds_p->scale1 = rw_scale = R_ScaleFromGlobalAngle(start);

    if (stop > start)
    {
        ds_p->scale2 = R_ScaleFromGlobalAngle(stop);
        ds_p->scalestep = rw_scalestep = (ds_p->scale2 - rw_scale) / (stop - start);
    }
    else
        ds_p->scale2 = ds_p->scale1;

    // calculate texture boundaries
    //  and decide if floor / ceiling marks are needed

    worldtop = frontsector->ceilingheight - viewz;
    worldbottom = frontsector->floorheight - viewz;

    midtexture = toptexture = bottomtexture = maskedtexture = 0;
    ds_p->maskedtexturecol = NULL;

    boolean markfloor, markceiling;

    if (!backsector)
    {
        // single sided line
        midtexture = texturetranslation[sidedef->midtexture];

        // a single sided line is terminal, so it must mark ends
        markfloor = markceiling = true;

        if (linedef->flags & ML_DONTPEGBOTTOM)
        {         // bottom of texture at bottom
            fixed_t vtop = frontsector->floorheight + ((int32_t)textureheight[sidedef->midtexture] << FRACBITS);
            rw_midtexturemid = vtop - viewz;
        }
        else        // top of texture at top
            rw_midtexturemid = worldtop;

        rw_midtexturemid += ((int32_t)Mod(sidedef->rowoffset, textureheight[midtexture])) << FRACBITS;

        ds_p->silhouette = SIL_BOTH;
        ds_p->sprtopclip = screenheightarray;
        ds_p->sprbottomclip = negonearray;
        ds_p->bsilheight = INT32_MAX;
        ds_p->tsilheight = INT32_MIN;
    }
    else      // two sided line
    {
        ds_p->sprtopclip = ds_p->sprbottomclip = NULL;
        ds_p->silhouette = SIL_NONE;

        if(linedata->r_flags & RF_CLOSED)
        { /* cph - closed 2S line e.g. door */
            // cph - killough's (outdated) comment follows - this deals with both
            // "automap fixes", his and mine
            // killough 1/17/98: this test is required if the fix
            // for the automap bug (r_bsp.c) is used, or else some
            // sprites will be displayed behind closed doors. That
            // fix prevents lines behind closed doors with dropoffs
            // from being displayed on the automap.

            ds_p->silhouette = SIL_BOTH;
            ds_p->sprtopclip = screenheightarray;
            ds_p->sprbottomclip = negonearray;
            ds_p->bsilheight = INT32_MAX;
            ds_p->tsilheight = INT32_MIN;

        }
        else
        { /* not solid - old code */

            if (frontsector->floorheight > backsector->floorheight)
            {
                ds_p->silhouette = SIL_BOTTOM;
                ds_p->bsilheight = frontsector->floorheight;
            }
            else
                if (backsector->floorheight > viewz)
                {
                    ds_p->silhouette = SIL_BOTTOM;
                    ds_p->bsilheight = INT32_MAX;
                }

            if (frontsector->ceilingheight < backsector->ceilingheight)
            {
                ds_p->silhouette |= SIL_TOP;
                ds_p->tsilheight = frontsector->ceilingheight;
            }
            else
                if (backsector->ceilingheight < viewz)
                {
                    ds_p->silhouette |= SIL_TOP;
                    ds_p->tsilheight = INT32_MIN;
                }
        }

        worldhigh = backsector->ceilingheight - viewz;
        worldlow = backsector->floorheight - viewz;

        // hack to allow height changes in outdoor areas
        if (frontsector->ceilingpic == skyflatnum && backsector->ceilingpic == skyflatnum)
            worldtop = worldhigh;

        markfloor = worldlow != worldbottom
                || backsector->floorpic != frontsector->floorpic
                || backsector->lightlevel != frontsector->lightlevel
                ;

        markceiling = worldhigh != worldtop
                || backsector->ceilingpic != frontsector->ceilingpic
                || backsector->lightlevel != frontsector->lightlevel
                ;

        if (backsector->ceilingheight <= frontsector->floorheight || backsector->floorheight >= frontsector->ceilingheight)
            markceiling = markfloor = true;   // closed door

        if (worldhigh < worldtop)   // top texture
        {
            toptexture = texturetranslation[sidedef->toptexture];
            rw_toptexturemid = linedef->flags & ML_DONTPEGTOP ? worldtop :
                                                                        backsector->ceilingheight + ((int32_t)textureheight[sidedef->toptexture] << FRACBITS) - viewz;
            rw_toptexturemid += ((int32_t)Mod(sidedef->rowoffset, textureheight[toptexture])) << FRACBITS;
        }

        if (worldlow > worldbottom) // bottom texture
        {
            bottomtexture = texturetranslation[sidedef->bottomtexture];
            rw_bottomtexturemid = linedef->flags & ML_DONTPEGBOTTOM ? worldtop : worldlow;

            rw_bottomtexturemid += ((int32_t)Mod(sidedef->rowoffset, textureheight[bottomtexture])) << FRACBITS;
        }

        // allocate space for masked texture tables
        if (sidedef->midtexture)    // masked midtexture
        {
            maskedtexture = true;
            ds_p->maskedtexturecol = maskedtexturecol = lastopening - rw_x;
            lastopening += rw_stopx - rw_x;
        }
    }

    // calculate rw_offset (only needed for textured lines)
    boolean segtextured = ((midtexture | toptexture | bottomtexture | maskedtexture) > 0);

    if (segtextured)
    {
        fixed_t rw_offset32 = hyp * -finesineapprox(offsetangle >> ANGLETOFINESHIFT_16);
        rw_offset32 += (((fixed_t)sidedef->textureoffset) << FRACBITS) + curline->offset;
        rw_offset = rw_offset32 >> FRACBITS;

        rw_centerangle = ANG90_16 + viewangle16 - rw_normalangle;

        rw_lightlevel = frontsector->lightlevel;
    }

    // if a floor / ceiling plane is on the wrong side of the view
    // plane, it is definitely invisible and doesn't need to be marked.
    if (frontsector->floorheight >= viewz)       // above view plane
        markfloor = false;
    if (frontsector->ceilingheight <= viewz &&
            frontsector->ceilingpic != skyflatnum)   // below view plane
        markceiling = false;

    // calculate incremental stepping values for texture edges
    worldtop    >>= 4;
    worldbottom >>= 4;

    topstep = -FixedMul(worldtop, rw_scalestep);
    topfrac = ((CENTERY * FRACUNIT) >> 4) - FixedMul(worldtop, rw_scale);

    bottomstep = -FixedMul(worldbottom, rw_scalestep);
    bottomfrac = ((CENTERY * FRACUNIT) >> 4) - FixedMul(worldbottom, rw_scale);

    if (backsector)
    {
        worldhigh >>= 4;
        worldlow  >>= 4;

        if (worldhigh < worldtop)
        {
            pixhigh = ((CENTERY * FRACUNIT) >> 4) - FixedMul(worldhigh, rw_scale);
            pixhighstep = -FixedMul(worldhigh, rw_scalestep);
        }
        if (worldlow > worldbottom)
        {
            pixlow = ((CENTERY * FRACUNIT) >> 4) - FixedMul(worldlow, rw_scale);
            pixlowstep = -FixedMul(worldlow, rw_scalestep);
        }
    }

    // render it
    if (markceiling)
    {
#if defined FLAT_SPAN
        if (ceilingplane_color == -1)
            markceiling = false;
#else
        if (ceilingplane)   // killough 4/11/98: add NULL ptr checks
            ceilingplane = R_CheckPlane (ceilingplane, rw_x, rw_stopx-1);
        else
            markceiling = false;
#endif
    }

    if (markfloor)
    {
#if defined FLAT_SPAN
        if (floorplane_color == -1)
            markfloor = false;
#else
        if (floorplane)     // killough 4/11/98: add NULL ptr checks
            /* cph 2003/04/18  - ceilingplane and floorplane might be the same
       * visplane (e.g. if both skies); R_CheckPlane doesn't know about
       * modifications to the plane that might happen in parallel with the check
       * being made, so we have to override it and split them anyway if that is
       * a possibility, otherwise the floor marking would overwrite the ceiling
       * marking, resulting in HOM. */
            if (markceiling && ceilingplane == floorplane)
                floorplane = R_DupPlane (floorplane, rw_x, rw_stopx-1);
            else
                floorplane = R_CheckPlane (floorplane, rw_x, rw_stopx-1);
        else
            markfloor = false;
#endif
    }

    didsolidcol = false;
    R_RenderSegLoop(rw_x, segtextured, markfloor, markceiling);

    /* cph - if a column was made solid by this wall, we _must_ save full clipping info */
    if (backsector && didsolidcol)
    {
        if (!(ds_p->silhouette & SIL_BOTTOM))
        {
            ds_p->silhouette |= SIL_BOTTOM;
            ds_p->bsilheight = backsector->floorheight;
        }
        if (!(ds_p->silhouette & SIL_TOP))
        {
            ds_p->silhouette |= SIL_TOP;
            ds_p->tsilheight = backsector->ceilingheight;
        }
    }

    // save sprite clipping info
    if ((ds_p->silhouette & SIL_TOP || maskedtexture) && !ds_p->sprtopclip)
    {
        memcpy((byte*)lastopening, (const byte*)(ceilingclip+start), sizeof(int16_t)*(rw_stopx-start));
        ds_p->sprtopclip = lastopening - start;
        lastopening += rw_stopx - start;
    }

    if ((ds_p->silhouette & SIL_BOTTOM || maskedtexture) && !ds_p->sprbottomclip)
    {
        memcpy((byte*)lastopening, (const byte*)(floorclip+start), sizeof(int16_t)*(rw_stopx-start));
        ds_p->sprbottomclip = lastopening - start;
        lastopening += rw_stopx - start;
    }

    if (maskedtexture && !(ds_p->silhouette & SIL_TOP))
    {
        ds_p->silhouette |= SIL_TOP;
        ds_p->tsilheight = INT32_MIN;
    }

    if (maskedtexture && !(ds_p->silhouette & SIL_BOTTOM))
    {
        ds_p->silhouette |= SIL_BOTTOM;
        ds_p->bsilheight = INT32_MAX;
    }

    ds_p++;
}


// killough 1/18/98 -- This function is used to fix the automap bug which
// showed lines behind closed doors simply because the door had a dropoff.
//
// cph - converted to R_RecalcLineFlags. This recalculates all the flags for
// a line, including closure and texture tiling.

static void R_RecalcLineFlags(void)
{
    linedata_t __far* linedata = &_g_linedata[linedef->lineno];

    const side_t __far* side = &_g_sides[curline->sidenum];

    linedata->r_validcount = _g_gametic;

    /* First decide if the line is closed, normal, or invisible */
    if (!(linedef->flags & ML_TWOSIDED)
            || backsector->ceilingheight <= frontsector->floorheight
            || backsector->floorheight >= frontsector->ceilingheight
            || (
                // if door is closed because back is shut:
                backsector->ceilingheight <= backsector->floorheight

                // preserve a kind of transparent door/lift special effect:
                && (backsector->ceilingheight >= frontsector->ceilingheight ||
                    side->toptexture)

                && (backsector->floorheight <= frontsector->floorheight ||
                    side->bottomtexture)

                // properly render skies (consider door "open" if both ceilings are sky):
                && (backsector->ceilingpic != skyflatnum ||
                    frontsector->ceilingpic!= skyflatnum)
                )
            )
        linedata->r_flags = (RF_CLOSED | (linedata->r_flags & ML_MAPPED));
    else
    {
        // Reject empty lines used for triggers
        //  and special events.
        // Identical floor and ceiling on both sides,
        // identical light levels on both sides,
        // and no middle texture.
        // CPhipps - recode for speed, not certain if this is portable though
        if (backsector->ceilingheight != frontsector->ceilingheight
                || backsector->floorheight != frontsector->floorheight
                || side->midtexture
                || backsector->ceilingpic != frontsector->ceilingpic
                || backsector->floorpic != frontsector->floorpic
                || backsector->lightlevel != frontsector->lightlevel)
        {
            linedata->r_flags = (linedata->r_flags & ML_MAPPED); return;
        } else
            linedata->r_flags = (RF_IGNORE | (linedata->r_flags & ML_MAPPED));
    }
}


// CPhipps -
// R_ClipWallSegment
//
// Replaces the old R_Clip*WallSegment functions. It draws bits of walls in those
// columns which aren't solid, and updates the solidcol[] array appropriately

static void R_ClipWallSegment(int16_t first, int16_t last, const boolean solid)
{
    byte *p;
    while (first < last)
    {
        if (solidcol[first])
        {
            if (!(p = memchr(solidcol+first, 0, last-first)))
                return; // All solid

            first = p - solidcol;
        }
        else
        {
            int16_t to;
            if (!(p = memchr(solidcol+first, 1, last-first)))
                to = last;
            else
                to = p - solidcol;

            R_StoreWallRange(first, to-1);

            if (solid)
            {
                memset(solidcol + first, 1, to - first);
            }

            first = to;
        }
    }
}

//
// R_ClearClipSegs
//

//
// R_AddLine
// Clips the given segment
// and adds any visible pieces to the line list.
//

static void R_AddLine(const seg_t __far* line)
{
    curline = line;

    angle16_t angle1 = R_PointToAngle(line->v1.x, line->v1.y);
    angle16_t angle2 = R_PointToAngle(line->v2.x, line->v2.y);

    // Clip to view edges.
    angle16_t span = angle1 - angle2;

    // Back side, i.e. backface culling
    if (span >= ANG180_16)
        return;

    // Global angle needed by segcalc.
    rw_angle1 = angle1;
    angle1 -= viewangle16;
    angle2 -= viewangle16;

    angle16_t tspan = angle1 + clipangle;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;

        // Totally off the left edge?
        if (tspan >= span)
            return;

        angle1 = clipangle;
    }

    tspan = clipangle - angle2;
    if (tspan > 2 * clipangle)
    {
        tspan -= 2 * clipangle;

        // Totally off the left edge?
        if (tspan >= span)
            return;
        angle2 = -clipangle;
    }

    // The seg is in the view range,
    // but not necessarily visible.

    // killough 1/31/98: Here is where "slime trails" can SOMETIMES occur:
    int8_t x1 = viewangletox((angle16_t)(angle1 + ANG90_16) >> ANGLETOFINESHIFT_16);
    int8_t x2 = viewangletox((angle16_t)(angle2 + ANG90_16) >> ANGLETOFINESHIFT_16);

    // Does not cross a pixel?
    if (x1 >= x2)       // killough 1/31/98 -- change == to >= for robustness
        return;

    backsector = line->backsectornum != NO_INDEX ? &_g_sectors[line->backsectornum] : NULL;

    /* cph - roll up linedef properties in flags */
    linedef = &_g_lines[curline->linenum];
    linedata_t __far* linedata = &_g_linedata[linedef->lineno];

    if (linedata->r_validcount != (uint16_t)_g_gametic)
        R_RecalcLineFlags();

    if (!(linedata->r_flags & RF_IGNORE))
    {
        R_ClipWallSegment (x1, x2, linedata->r_flags & RF_CLOSED);
    }
}

//
// R_Subsector
// Determine floor/ceiling planes.
// Add sprites of things in sector.
// Draw one or more line segments.
//

static void R_Subsector(int16_t num)
{
    int16_t         count;
    const seg_t       __far* line;
    subsector_t __far* sub;

    sub = &_g_subsectors[num];
    frontsector = sub->sector;
    count = sub->numlines;
    line = &_g_segs[sub->firstline];

#if defined FLAT_SPAN
    if (frontsector->floorheight < viewz)
        floorplane_color = R_GetPlaneColor(frontsector->floorpic, frontsector->lightlevel);
    else
        floorplane_color = -1;
#else
    if(frontsector->floorheight < viewz)
    {
        floorplane = R_FindPlane(frontsector->floorheight,
                                     frontsector->floorpic,
                                     frontsector->lightlevel                // killough 3/16/98
                                     );
    }
    else
    {
        floorplane = NULL;
    }
#endif


#if defined FLAT_SPAN
    if (frontsector->ceilingpic == skyflatnum) {
        ceilingplane_color = -2;
        R_LoadSkyPatch();
    } else if (frontsector->ceilingheight > viewz)
        ceilingplane_color = R_GetPlaneColor(frontsector->ceilingpic, frontsector->lightlevel);
    else
        ceilingplane_color = -1;
#else
    if(frontsector->ceilingheight > viewz || (frontsector->ceilingpic == skyflatnum))
    {
        ceilingplane = R_FindPlane(frontsector->ceilingheight,     // killough 3/8/98
                                       frontsector->ceilingpic,
                                       frontsector->lightlevel
                                       );
    }
    else
    {
        ceilingplane = NULL;
    }
#endif

    R_AddSprites(sub, frontsector->lightlevel);
    while (count--)
    {
        R_AddLine (line);
        line++;
        curline = NULL; /* cph 2001/11/18 - must clear curline now we're done with it, so R_LoadColorMap doesn't try using it for other things */
    }
}

//
// R_CheckBBox
// Checks BSP node/subtree bounding box.
// Returns true
//  if some part of the bbox might be visible.
//

static const byte checkcoord[12][4] =
{
  {3,0,2,1},
  {3,0,2,0},
  {3,1,2,0},
  {0},
  {2,0,2,1},
  {0,0,0,0},
  {3,1,3,0},
  {0},
  {2,0,3,1},
  {2,1,3,1},
  {2,1,3,0}
};


static boolean R_CheckBBox(const int16_t __far* bspcoord)
{
    // Find the corners of the box
    // that define the edges from current viewpoint.
    int16_t boxpos = (viewx <= ((fixed_t)bspcoord[BOXLEFT]<<FRACBITS) ? 0 : viewx < ((fixed_t)bspcoord[BOXRIGHT]<<FRACBITS) ? 1 : 2) +
            (viewy >= ((fixed_t)bspcoord[BOXTOP]<<FRACBITS) ? 0 : viewy > ((fixed_t)bspcoord[BOXBOTTOM]<<FRACBITS) ? 4 : 8);

    if (boxpos == 5)
        return true;

    const byte* check = checkcoord[boxpos];
    angle16_t angle1 = R_PointToAngle16(bspcoord[check[0]], bspcoord[check[1]]) - viewangle16;
    angle16_t angle2 = R_PointToAngle16(bspcoord[check[2]], bspcoord[check[3]]) - viewangle16;


    // cph - replaced old code, which was unclear and badly commented
    // Much more efficient code now
    if ((int16_t)angle1 < (int16_t)angle2)
    { /* it's "behind" us */
        /* Either angle1 or angle2 is behind us, so it doesn't matter if we
     * change it to the corect sign
     */
        if (ANG180_16 <= angle1 && angle1 < ANG270_16)
            angle1 = INT16_MAX; /* which is ANG180_16 - 1 */
        else
            angle2 = INT16_MIN;
    }

    if ((int16_t)angle2 >=  (int16_t)clipangle) return false; // Both off left edge
    if ((int16_t)angle1 <= -(int16_t)clipangle) return false; // Both off right edge
    if ((int16_t)angle1 >=  (int16_t)clipangle) angle1 =  clipangle; // Clip at left edge
    if ((int16_t)angle2 <= -(int16_t)clipangle) angle2 = -clipangle; // Clip at right edge

    // Find the first clippost
    //  that touches the source post
    //  (adjacent pixels are touching).

    int8_t sx1 = viewangletox((angle16_t)(angle1 + ANG90_16) >> ANGLETOFINESHIFT_16);
    int8_t sx2 = viewangletox((angle16_t)(angle2 + ANG90_16) >> ANGLETOFINESHIFT_16);
    //    const cliprange_t *start;

    // Does not cross a pixel.
    if (sx1 == sx2)
        return false;

    if (!memchr(solidcol+sx1, 0, sx2-sx1)) return false;
    // All columns it covers are already solidly covered


    return true;
}

//Render a BSP subsector if bspnum is a leaf node.
//Return false if bspnum is frame node.





static boolean R_RenderBspSubsector(int16_t bspnum)
{
    // Found a subsector?
    if (bspnum & NF_SUBSECTOR)
    {
        if (bspnum == -1)
            R_Subsector (0);
        else
            R_Subsector (bspnum & (~NF_SUBSECTOR));

        return true;
    }

    return false;
}

// RenderBSPNode
// Renders all subsectors below a given node,
//  traversing subtree recursively.
// Just call with BSP root.

#if defined PROFILING
//Non recursive version.
//constant stack space used and easier to
//performance profile.
#define MAX_BSP_DEPTH 128

static void R_RenderBSPNode(int16_t bspnum)
{
    int16_t stack[MAX_BSP_DEPTH];
    int16_t sp = 0;

    const mapnode_t __far* bsp;
    int16_t side = 0;

    while(true)
    {
        //Front sides.
        while (!R_RenderBspSubsector(bspnum))
        {
            if(sp == MAX_BSP_DEPTH)
                break;

            bsp = &nodes[bspnum];
            side = R_PointOnSide (viewx, viewy, bsp);

            stack[sp++] = bspnum;
            stack[sp++] = side;

            bspnum = bsp->children[side];
        }

        if(sp == 0)
        {
            //back at root node and not visible. All done!
            return;
        }

        //Back sides.
        side = stack[--sp];
        bspnum = stack[--sp];
        bsp = &nodes[bspnum];

        // Possibly divide back space.
        //Walk back up the tree until we find
        //a node that has a visible backspace.
        while(!R_CheckBBox (bsp->bbox[side^1]))
        {
            if(sp == 0)
            {
                //back at root node and not visible. All done!
                return;
            }

            //Back side next.
            side = stack[--sp];
            bspnum = stack[--sp];

            bsp = &nodes[bspnum];
        }

        bspnum = bsp->children[side^1];
    }
}
#else
static void R_RenderBSPNode(int16_t bspnum)
{
	if (R_RenderBspSubsector(bspnum))
		return;

	const mapnode_t __far* bsp = &nodes[bspnum];

//
// decide which side the view point is on
//
	int16_t side = R_PointOnSide(viewx, viewy, bsp);

	R_RenderBSPNode(bsp->children[side]); // recursively divide front space

	if (R_CheckBBox(bsp->bbox[side ^ 1]))	// possibly divide back space
		R_RenderBSPNode(bsp->children[side ^ 1]);
}
#endif


static void R_ClearDrawSegs(void)
{
    ds_p = _s_drawsegs;
}

static void R_ClearClipSegs (void)
{
    memset(solidcol, 0, VIEWWINDOWWIDTH);
}


//
// R_SetupFrame
//

static void R_SetupFrame (player_t *player)
{
    viewx = player->mo->x;
    viewy = player->mo->y;
    viewz = player->viewz;
    viewangle = player->mo->angle;
    viewangle16 = viewangle >> FRACBITS;

    extralight = player->extralight;

    viewsin = finesineapprox(  viewangle16 >> ANGLETOFINESHIFT_16);
    viewcos = finecosineapprox(viewangle16 >> ANGLETOFINESHIFT_16);

    if (player->fixedcolormap)
    {
        fixedcolormap = fullcolormap   // killough 3/20/98: use fullcolormap
                + player->fixedcolormap*256;
    }
    else
        fixedcolormap = NULL;

    validcount++;
}


//
// R_RenderView
//
void R_RenderPlayerView (player_t* player)
{
    R_SetupFrame (player);

    // Clear buffers.
    R_ClearClipSegs ();
    R_ClearDrawSegs ();
    R_ClearOpeningClippingDetermination ();

#if !defined FLAT_SPAN
    R_ClearPlanes ();
#endif

    R_ClearOpenings ();
    R_ClearSprites ();

    // The head node is the last node output.
    R_RenderBSPNode (numnodes-1);

#if defined FLAT_SPAN
    R_FreeSkyPatch ();
#else
    R_DrawPlanes ();
#endif

    R_DrawMasked ();
}


static const int8_t viewangletoxTable[2027] =
{
    59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59, 59,
    58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58,
    57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57,
    56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56,
    55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55,
    54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
    53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53,
    52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52,
    51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51,
    50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50,
    49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,
    48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
    47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
    46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
    45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
    44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44,
    43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43,
    42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
    41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
    40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,
    39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39,
    38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38,
    37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37,
    36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
    35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35,
    34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34,
    33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33,
    32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32,
    31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31,
    30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
    29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
    28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
    27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
    26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
    25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
    20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
    19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19,
    18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18,
    17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
    14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
    13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
    11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
    10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
};


// ArcTan LUT,
//  maps tan(angle) to angle fast. Gotta search.
//
// Effective size is 2049;
// The +1 size is to handle the case when x==y without additional checking.
static const angle_t tantoangleTable[2049] =
{
    0,333772,667544,1001315,1335086,1668857,2002626,2336395,
    2670163,3003929,3337694,3671457,4005219,4338979,4672736,5006492,
    5340245,5673995,6007743,6341488,6675230,7008968,7342704,7676435,
    8010164,8343888,8677609,9011325,9345037,9678744,10012447,10346145,
    10679838,11013526,11347209,11680887,12014558,12348225,12681885,13015539,
    13349187,13682829,14016464,14350092,14683714,15017328,15350936,15684536,
    16018129,16351714,16685291,17018860,17352422,17685974,18019518,18353054,
    18686582,19020100,19353610,19687110,20020600,20354080,20687552,21021014,
    21354466,21687906,22021338,22354758,22688168,23021568,23354956,23688332,
    24021698,24355052,24688396,25021726,25355046,25688352,26021648,26354930,
    26688200,27021456,27354702,27687932,28021150,28354356,28687548,29020724,
    29353888,29687038,30020174,30353296,30686404,31019496,31352574,31685636,
    32018684,32351718,32684734,33017736,33350722,33683692,34016648,34349584,
    34682508,35015412,35348300,35681172,36014028,36346868,36679688,37012492,
    37345276,37678044,38010792,38343524,38676240,39008936,39341612,39674272,
    40006912,40339532,40672132,41004716,41337276,41669820,42002344,42334848,
    42667332,42999796,43332236,43664660,43997060,44329444,44661800,44994140,
    45326456,45658752,45991028,46323280,46655512,46987720,47319908,47652072,
    47984212,48316332,48648428,48980500,49312548,49644576,49976580,50308556,
    50640512,50972444,51304352,51636236,51968096,52299928,52631740,52963524,
    53295284,53627020,53958728,54290412,54622068,54953704,55285308,55616888,
    55948444,56279972,56611472,56942948,57274396,57605816,57937212,58268576,
    58599916,58931228,59262512,59593768,59924992,60256192,60587364,60918508,
    61249620,61580704,61911760,62242788,62573788,62904756,63235692,63566604,
    63897480,64228332,64559148,64889940,65220696,65551424,65882120,66212788,
    66543420,66874024,67204600,67535136,67865648,68196120,68526568,68856984,
    69187360,69517712,69848024,70178304,70508560,70838776,71168960,71499112,
    71829224,72159312,72489360,72819376,73149360,73479304,73809216,74139096,
    74468936,74798744,75128520,75458264,75787968,76117632,76447264,76776864,
    77106424,77435952,77765440,78094888,78424304,78753688,79083032,79412336,
    79741608,80070840,80400032,80729192,81058312,81387392,81716432,82045440,
    82374408,82703336,83032224,83361080,83689896,84018664,84347400,84676096,
    85004760,85333376,85661952,85990488,86318984,86647448,86975864,87304240,
    87632576,87960872,88289128,88617344,88945520,89273648,89601736,89929792,
    90257792,90585760,90913688,91241568,91569408,91897200,92224960,92552672,
    92880336,93207968,93535552,93863088,94190584,94518040,94845448,95172816,
    95500136,95827416,96154648,96481832,96808976,97136080,97463136,97790144,
    98117112,98444032,98770904,99097736,99424520,99751256,100077944,100404592,
    100731192,101057744,101384248,101710712,102037128,102363488,102689808,103016080,
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    501811072,501995008,502178848,502362592,502546240,502729824,502913312,503096704,
    503280000,503463232,503646368,503829408,504012352,504195200,504377984,504560672,
    504743264,504925760,505108192,505290496,505472736,505654912,505836960,506018944,
    506200832,506382624,506564320,506745952,506927488,507108928,507290272,507471552,
    507652736,507833824,508014816,508195744,508376576,508557312,508737952,508918528,
    509099008,509279392,509459680,509639904,509820032,510000064,510180000,510359872,
    510539648,510719328,510898944,511078432,511257856,511437216,511616448,511795616,
    511974688,512153664,512332576,512511392,512690112,512868768,513047296,513225792,
    513404160,513582432,513760640,513938784,514116800,514294752,514472608,514650368,
    514828064,515005664,515183168,515360608,515537952,515715200,515892352,516069440,
    516246432,516423328,516600160,516776896,516953536,517130112,517306592,517482976,
    517659264,517835488,518011616,518187680,518363648,518539520,518715296,518891008,
    519066624,519242144,519417600,519592960,519768256,519943424,520118528,520293568,
    520468480,520643328,520818112,520992800,521167392,521341888,521516320,521690656,
    521864896,522039072,522213152,522387168,522561056,522734912,522908640,523082304,
    523255872,523429376,523602784,523776096,523949312,524122464,524295552,524468512,
    524641440,524814240,524986976,525159616,525332192,525504640,525677056,525849344,
    526021568,526193728,526365792,526537760,526709632,526881440,527053152,527224800,
    527396352,527567840,527739200,527910528,528081728,528252864,528423936,528594880,
    528765760,528936576,529107296,529277920,529448480,529618944,529789344,529959648,
    530129856,530300000,530470048,530640000,530809888,530979712,531149440,531319072,
    531488608,531658080,531827488,531996800,532166016,532335168,532504224,532673184,
    532842080,533010912,533179616,533348288,533516832,533685312,533853728,534022048,
    534190272,534358432,534526496,534694496,534862400,535030240,535197984,535365632,
    535533216,535700704,535868128,536035456,536202720,536369888,536536992,536704000,
    536870912
};


// Tangens LUT.
// Should work with BAM fairly well (12 of 16bit, effectively, by shifting).
static const uint16_t finetangentTable_part_3[1024] =
{
    25,75,125,175,226,276,326,376,
    427,477,527,578,628,678,728,779,
    829,879,929,980,1030,1080,1131,1181,
    1231,1281,1332,1382,1432,1483,1533,1583,
    1633,1684,1734,1784,1835,1885,1935,1986,
    2036,2086,2137,2187,2237,2288,2338,2388,
    2439,2489,2539,2590,2640,2690,2741,2791,
    2841,2892,2942,2992,3043,3093,3144,3194,
    3244,3295,3345,3395,3446,3496,3547,3597,
    3648,3698,3748,3799,3849,3900,3950,4001,
    4051,4101,4152,4202,4253,4303,4354,4404,
    4455,4505,4556,4606,4657,4707,4758,4808,
    4859,4910,4960,5011,5061,5112,5162,5213,
    5264,5314,5365,5415,5466,5517,5567,5618,
    5668,5719,5770,5820,5871,5922,5972,6023,
    6074,6124,6175,6226,6277,6327,6378,6429,
    6480,6530,6581,6632,6683,6733,6784,6835,
    6886,6937,6988,7038,7089,7140,7191,7242,
    7293,7344,7395,7445,7496,7547,7598,7649,
    7700,7751,7802,7853,7904,7955,8006,8057,
    8108,8159,8210,8261,8312,8363,8414,8466,
    8517,8568,8619,8670,8721,8772,8824,8875,
    8926,8977,9028,9080,9131,9182,9233,9285,
    9336,9387,9438,9490,9541,9592,9644,9695,
    9747,9798,9849,9901,9952,10004,10055,10106,
    10158,10209,10261,10312,10364,10415,10467,10519,
    10570,10622,10673,10725,10777,10828,10880,10931,
    10983,11035,11086,11138,11190,11242,11293,11345,
    11397,11449,11501,11552,11604,11656,11708,11760,
    11812,11864,11916,11967,12019,12071,12123,12175,
    12227,12279,12331,12383,12436,12488,12540,12592,
    12644,12696,12748,12800,12853,12905,12957,13009,
    13062,13114,13166,13218,13271,13323,13375,13428,
    13480,13533,13585,13637,13690,13742,13795,13847,
    13900,13952,14005,14057,14110,14163,14215,14268,
    14321,14373,14426,14479,14531,14584,14637,14690,
    14743,14795,14848,14901,14954,15007,15060,15113,
    15166,15219,15272,15325,15378,15431,15484,15537,
    15590,15643,15696,15749,15802,15856,15909,15962,
    16015,16069,16122,16175,16229,16282,16335,16389,
    16442,16496,16549,16603,16656,16710,16763,16817,
    16870,16924,16977,17031,17085,17138,17192,17246,
    17300,17353,17407,17461,17515,17569,17623,17677,
    17731,17784,17838,17892,17946,18001,18055,18109,
    18163,18217,18271,18325,18380,18434,18488,18542,
    18597,18651,18705,18760,18814,18868,18923,18977,
    19032,19086,19141,19195,19250,19305,19359,19414,
    19469,19523,19578,19633,19688,19742,19797,19852,
    19907,19962,20017,20072,20127,20182,20237,20292,
    20347,20402,20457,20513,20568,20623,20678,20734,
    20789,20844,20900,20955,21010,21066,21121,21177,
    21232,21288,21343,21399,21455,21510,21566,21622,
    21678,21733,21789,21845,21901,21957,22013,22069,
    22125,22181,22237,22293,22349,22405,22461,22517,
    22573,22630,22686,22742,22799,22855,22911,22968,
    23024,23081,23137,23194,23250,23307,23364,23420,
    23477,23534,23591,23647,23704,23761,23818,23875,
    23932,23989,24046,24103,24160,24217,24274,24331,
    24389,24446,24503,24560,24618,24675,24732,24790,
    24847,24905,24962,25020,25078,25135,25193,25251,
    25308,25366,25424,25482,25540,25598,25656,25714,
    25772,25830,25888,25946,26004,26062,26120,26179,
    26237,26295,26354,26412,26471,26529,26588,26646,
    26705,26763,26822,26881,26940,26998,27057,27116,
    27175,27234,27293,27352,27411,27470,27529,27588,
    27647,27707,27766,27825,27884,27944,28003,28063,
    28122,28182,28241,28301,28361,28420,28480,28540,
    28600,28660,28719,28779,28839,28899,28959,29020,
    29080,29140,29200,29260,29321,29381,29441,29502,
    29562,29623,29683,29744,29805,29865,29926,29987,
    30048,30108,30169,30230,30291,30352,30413,30474,
    30536,30597,30658,30719,30781,30842,30904,30965,
    31026,31088,31150,31211,31273,31335,31396,31458,
    31520,31582,31644,31706,31768,31830,31892,31955,
    32017,32079,32141,32204,32266,32329,32391,32454,
    32516,32579,32642,32705,32767,32830,32893,32956,
    33019,33082,33145,33208,33272,33335,33398,33461,
    33525,33588,33652,33715,33779,33843,33906,33970,
    34034,34098,34162,34225,34289,34354,34418,34482,
    34546,34610,34675,34739,34803,34868,34932,34997,
    35062,35126,35191,35256,35321,35385,35450,35515,
    35580,35646,35711,35776,35841,35907,35972,36037,
    36103,36168,36234,36300,36365,36431,36497,36563,
    36629,36695,36761,36827,36893,36959,37026,37092,
    37158,37225,37291,37358,37425,37491,37558,37625,
    37692,37759,37826,37893,37960,38027,38094,38161,
    38229,38296,38364,38431,38499,38566,38634,38702,
    38770,38837,38905,38973,39042,39110,39178,39246,
    39314,39383,39451,39520,39588,39657,39726,39794,
    39863,39932,40001,40070,40139,40208,40278,40347,
    40416,40486,40555,40625,40694,40764,40834,40904,
    40973,41043,41113,41184,41254,41324,41394,41465,
    41535,41605,41676,41747,41817,41888,41959,42030,
    42101,42172,42243,42314,42385,42457,42528,42600,
    42671,42743,42814,42886,42958,43030,43102,43174,
    43246,43318,43390,43463,43535,43608,43680,43753,
    43826,43898,43971,44044,44117,44190,44263,44337,
    44410,44483,44557,44630,44704,44778,44851,44925,
    44999,45073,45147,45221,45296,45370,45444,45519,
    45593,45668,45743,45818,45892,45967,46042,46118,
    46193,46268,46343,46419,46494,46570,46646,46721,
    46797,46873,46949,47025,47102,47178,47254,47331,
    47407,47484,47560,47637,47714,47791,47868,47945,
    48022,48100,48177,48255,48332,48410,48488,48565,
    48643,48721,48799,48878,48956,49034,49113,49191,
    49270,49349,49427,49506,49585,49664,49744,49823,
    49902,49982,50061,50141,50221,50300,50380,50460,
    50540,50621,50701,50781,50862,50942,51023,51104,
    51185,51266,51347,51428,51509,51591,51672,51754,
    51835,51917,51999,52081,52163,52245,52327,52410,
    52492,52575,52657,52740,52823,52906,52989,53072,
    53156,53239,53322,53406,53490,53574,53657,53741,
    53826,53910,53994,54079,54163,54248,54333,54417,
    54502,54587,54673,54758,54843,54929,55015,55100,
    55186,55272,55358,55444,55531,55617,55704,55790,
    55877,55964,56051,56138,56225,56312,56400,56487,
    56575,56663,56751,56839,56927,57015,57104,57192,
    57281,57369,57458,57547,57636,57725,57815,57904,
    57994,58083,58173,58263,58353,58443,58534,58624,
    58715,58805,58896,58987,59078,59169,59261,59352,
    59444,59535,59627,59719,59811,59903,59996,60088,
    60181,60273,60366,60459,60552,60646,60739,60833,
    60926,61020,61114,61208,61302,61396,61491,61585,
    61680,61775,61870,61965,62060,62156,62251,62347,
    62443,62539,62635,62731,62828,62924,63021,63118,
    63215,63312,63409,63506,63604,63702,63799,63897,
    63996,64094,64192,64291,64389,64488,64587,64687,
    64786,64885,64985,65085,65185,65285,65385,65485
};

static const fixed_t finetangentTable_part_4[1024] =
{
    65586,65686,65787,65888,65989,66091,66192,66294,
    66396,66498,66600,66702,66804,66907,67010,67113,
    67216,67319,67422,67526,67629,67733,67837,67942,
    68046,68151,68255,68360,68465,68570,68676,68781,
    68887,68993,69099,69205,69312,69418,69525,69632,
    69739,69846,69954,70061,70169,70277,70385,70494,
    70602,70711,70820,70929,71038,71147,71257,71367,
    71477,71587,71697,71808,71918,72029,72140,72252,
    72363,72475,72587,72699,72811,72923,73036,73149,
    73262,73375,73488,73602,73715,73829,73944,74058,
    74172,74287,74402,74517,74633,74748,74864,74980,
    75096,75213,75329,75446,75563,75680,75797,75915,
    76033,76151,76269,76388,76506,76625,76744,76864,
    76983,77103,77223,77343,77463,77584,77705,77826,
    77947,78068,78190,78312,78434,78557,78679,78802,
    78925,79048,79172,79296,79420,79544,79668,79793,
    79918,80043,80168,80294,80420,80546,80672,80799,
    80925,81053,81180,81307,81435,81563,81691,81820,
    81949,82078,82207,82336,82466,82596,82726,82857,
    82987,83118,83250,83381,83513,83645,83777,83910,
    84043,84176,84309,84443,84576,84710,84845,84980,
    85114,85250,85385,85521,85657,85793,85930,86066,
    86204,86341,86479,86616,86755,86893,87032,87171,
    87310,87450,87590,87730,87871,88011,88152,88294,
    88435,88577,88720,88862,89005,89148,89292,89435,
    89579,89724,89868,90013,90158,90304,90450,90596,
    90742,90889,91036,91184,91332,91480,91628,91777,
    91926,92075,92225,92375,92525,92675,92826,92978,
    93129,93281,93434,93586,93739,93892,94046,94200,
    94354,94509,94664,94819,94975,95131,95287,95444,
    95601,95758,95916,96074,96233,96391,96551,96710,
    96870,97030,97191,97352,97513,97675,97837,98000,
    98163,98326,98489,98653,98818,98982,99148,99313,
    99479,99645,99812,99979,100146,100314,100482,100651,
    100820,100990,101159,101330,101500,101671,101843,102015,
    102187,102360,102533,102706,102880,103054,103229,103404,
    103580,103756,103933,104109,104287,104465,104643,104821,
    105000,105180,105360,105540,105721,105902,106084,106266,
    106449,106632,106816,107000,107184,107369,107555,107741,
    107927,108114,108301,108489,108677,108866,109055,109245,
    109435,109626,109817,110008,110200,110393,110586,110780,
    110974,111169,111364,111560,111756,111952,112150,112347,
    112546,112744,112944,113143,113344,113545,113746,113948,
    114151,114354,114557,114761,114966,115171,115377,115583,
    115790,115998,116206,116414,116623,116833,117044,117254,
    117466,117678,117891,118104,118318,118532,118747,118963,
    119179,119396,119613,119831,120050,120269,120489,120709,
    120930,121152,121374,121597,121821,122045,122270,122496,
    122722,122949,123176,123404,123633,123863,124093,124324,
    124555,124787,125020,125254,125488,125723,125959,126195,
    126432,126669,126908,127147,127387,127627,127869,128111,
    128353,128597,128841,129086,129332,129578,129825,130073,
    130322,130571,130821,131072,131324,131576,131830,132084,
    132339,132594,132851,133108,133366,133625,133884,134145,
    134406,134668,134931,135195,135459,135725,135991,136258,
    136526,136795,137065,137335,137607,137879,138152,138426,
    138701,138977,139254,139532,139810,140090,140370,140651,
    140934,141217,141501,141786,142072,142359,142647,142936,
    143226,143517,143808,144101,144395,144690,144986,145282,
    145580,145879,146179,146480,146782,147084,147388,147693,
    148000,148307,148615,148924,149235,149546,149859,150172,
    150487,150803,151120,151438,151757,152077,152399,152722,
    153045,153370,153697,154024,154352,154682,155013,155345,
    155678,156013,156349,156686,157024,157363,157704,158046,
    158389,158734,159079,159427,159775,160125,160476,160828,
    161182,161537,161893,162251,162610,162970,163332,163695,
    164060,164426,164793,165162,165532,165904,166277,166651,
    167027,167405,167784,168164,168546,168930,169315,169701,
    170089,170479,170870,171263,171657,172053,172451,172850,
    173251,173653,174057,174463,174870,175279,175690,176102,
    176516,176932,177349,177769,178190,178612,179037,179463,
    179891,180321,180753,181186,181622,182059,182498,182939,
    183382,183827,184274,184722,185173,185625,186080,186536,
    186995,187455,187918,188382,188849,189318,189789,190261,
    190736,191213,191693,192174,192658,193143,193631,194122,
    194614,195109,195606,196105,196606,197110,197616,198125,
    198636,199149,199664,200182,200703,201226,201751,202279,
    202809,203342,203878,204416,204956,205500,206045,206594,
    207145,207699,208255,208815,209376,209941,210509,211079,
    211652,212228,212807,213389,213973,214561,215151,215745,
    216341,216941,217544,218149,218758,219370,219985,220603,
    221225,221849,222477,223108,223743,224381,225022,225666,
    226314,226966,227621,228279,228941,229606,230275,230948,
    231624,232304,232988,233676,234367,235062,235761,236463,
    237170,237881,238595,239314,240036,240763,241493,242228,
    242967,243711,244458,245210,245966,246727,247492,248261,
    249035,249813,250596,251384,252176,252973,253774,254581,
    255392,256208,257029,257855,258686,259522,260363,261209,
    262060,262917,263779,264646,265519,266397,267280,268169,
    269064,269965,270871,271782,272700,273624,274553,275489,
    276430,277378,278332,279292,280258,281231,282210,283195,
    284188,285186,286192,287204,288223,289249,290282,291322,
    292369,293423,294485,295554,296630,297714,298805,299904,
    301011,302126,303248,304379,305517,306664,307819,308983,
    310154,311335,312524,313721,314928,316143,317368,318601,
    319844,321097,322358,323629,324910,326201,327502,328812,
    330133,331464,332805,334157,335519,336892,338276,339671,
    341078,342495,343924,345364,346816,348280,349756,351244,
    352744,354257,355783,357321,358872,360436,362013,363604,
    365208,366826,368459,370105,371765,373440,375130,376835,
    378555,380290,382040,383807,385589,387387,389202,391034,
    392882,394747,396630,398530,400448,402384,404338,406311,
    408303,410314,412344,414395,416465,418555,420666,422798,
    424951,427125,429321,431540,433781,436045,438332,440643,
    442978,445337,447720,450129,452564,455024,457511,460024,
    462565,465133,467730,470355,473009,475692,478406,481150,
    483925,486732,489571,492443,495348,498287,501261,504269,
    507313,510394,513512,516667,519861,523094,526366,529680,
    533034,536431,539870,543354,546881,550455,554074,557741,
    561456,565221,569035,572901,576818,580789,584815,588896,
    593033,597229,601483,605798,610174,614613,619117,623686,
    628323,633028,637803,642651,647572,652568,657640,662792,
    668024,673338,678737,684223,689797,695462,701219,707072,
    713023,719074,725227,731486,737853,744331,750922,757631,
    764460,771411,778490,785699,793041,800521,808143,815910,
    823827,831898,840127,848520,857081,865817,874730,883829,
    893117,902602,912289,922186,932298,942633,953199,964003,
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