Exporting motions to bvh

[aplatyps]

Hi Chen Xin, love your work. I'm currently learning about 3D motions (very new to this, might ask silly questions) and came across your paper and GitHub after some research. I generated some motions with your pre-trained model with the HumanML3D dataset. There's 22 joints. If I understood your paper correctly, the motion generated is in MMM format, and you have a list of joint names arranged in a way that's corresponding to the index of the generated motion. I'm currently trying to write a script to export the motions to a .bvh file so it's easier to use. Do you know of any existing methods/tools I can use or if I need to do any transformation on the motion? Many thanks :)

[ChenFengYe]

Welcome to motion generation!
The generated motion is not in MMM format (21 joints). It is AMASS format (22 joints). Please refer to the below.

motion-latent-diffusion/mld/transforms/joints2rots/config.py

Line 71 in 7db8623

AMASS_JOINT_MAP = {

If you want to export .bvh file, we suggest you fit smpl motion parameters (root position+joint rotation).
You can check this part in github page readme. Then, export smpl motion parameters to bvh file. There are many scripts, e.g. https://github.com/KosukeFukazawa/smpl2bvh
You can also find more related tools.

[aplatyps]

Thanks for the pointers, it was very helpful!
I see that you have 3 params in the exported smpl .pkl

motion-latent-diffusion/fit.py

Lines 272 to 274 in d6c5ca7

	param["beta"] = new_opt_betas.detach().cpu().numpy()
	param["pose"] = new_opt_pose.detach().cpu().numpy()
	param["cam"] = new_opt_cam_t.detach().cpu().numpy()

poses is the rotation vectors, I assume the cam is the global translation. Where can I find the smpl scaling?

[ChenFengYe]

I am not sure what in "cam". Maybe zeros?
"pose" should be 72 (3 root global translation + 3*23 local rotation with 23 joints).
No scaling here, maybe "cam" is a kind of scales?