TotalCapture: trajectory in original VS trajectory in AMASS

[glisca]

Hi there,

please help me understand which "scale factor" or something else am I missing. Here is my experiment:

1. load the ./amass/TotalCapture/s1/acting1_poses.npz

2. iterate trough the first 250 frames

   • put the SMPL model at the global location and orientation in the configuration specified by the current frame.
   • take the 3D coordinates of SMPL's 1962 vertex (approx. on the left wrist) multiply them with the transformation matrix and save them into into
     • 
     • 
   • collect all into left_wrist_amass_trj

3. load the acting1_BlenderZXY_YmZ.bvh ground truth data from the TotalCapture

   • while loading, convert the values from centimeters into meters

4. iterate trough the first 250 frames

   • save the 3D coordinates of the LeftHand joint into left_wrist_total_trj.

5. plot left_wrist_amass_trj with blue and left_wrist_total_trj with orange in the coordinates systems of the total capture and obtain this plot:
   

The two trajectories describe the first 250 points trough which the left wrist passes relative to the global coordinates system of total capture. They seem to have the same curvature. The orange trajectory (loaded from the *.bvh file) seems to be downscale with respect to the blue trajectory (transformed loaded from amass).

I overlooked the fact that the ground truth from the *.bvh files is in inches. After converting it into centimeters then into meters the plots of the left_wrist_amass_trj and left_wrist_total_trj look more similar, though still don't overlap.

Could you please help me figure out why they don't overlap closely? I think the offset between them is still to big.

Many thanks in advance!

[YujiaoHao]

hi, I'm facing a similar problem to yours. Do you have any updates?
Thank you in advance!

[glisca]

Hi there, unfortunately I have no updates. I had to focus on other topics and this one remained hanging.
Kind regards,

[nghorbani]

lets set up a debugging scenario.
forget about the bvh and only get a smpl in pose_body = 0, trans=0, root_orient=0.
now transform the vertices (or a subset) it to a location you desire using your transformation technique. now pose the smpl body using trans and root orient.
If the two bodies overlap then your transformation code is correct. if not then debug is needed.
Please note that the root joint might not be at zero location. That means in a zero tpose smpl body (i.e. pose_body = 0, trans=0, root_orient=0) if you do bm.Jtr.view(1, -1, 3)[:,0]) then the value is slightly above zero. This would change the center of all transformations.
let me know if you need more help on this.