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A simple question about camera and coordinate system.

See original GitHub issue

Hi, I have a simple question about ROMP. I have been struggling putting people into their correct relative position, but is it really possible using the root-aligned SMPL meshes without predicting their transl? (And if we have camera param K, will it be possible? )

  1. What is the coordinate system of the vertices that are used for rendering? I think we are predicting camera coordinate system points but root-aligned, correct?

  2. Following Q1, before rendering verts onto image, there is a trans added to verts ('cam_trans in') What is it? and what is estimate_translation actually doing? Is this estimating root’s position?

  3. I tried to replace the verts +trans in Q2 with GT mesh, so verts=GT_verts, without any other changes to your code, but the results are not correct, I expect it to be fully matched the person on the image but there are always shifts, and I also can’t use the same FOV otherwise it would be a very small mesh on the image.

Sorry if I understand anything wrong. I think rendering is the final part I didn’t understand in your code. Looking forward you for your answer!


Issue Analytics

  • State:closed
  • Created a year ago
  • Comments:24 (10 by maintainers)

github_iconTop GitHub Comments

ZhengdiYucommented, Apr 21, 2022


@ZhengdiYu , Zhengdi, Please check this function:

Camera coordinate system is defined by the proj_mat in this function. Therefore, if you want to get the predicted translation is GT Camera coordinate system, you just need to provide the right proj_mat, which is commonly called extrinsic & intrinsic camera matrix / camera projection matrix. If you understand estimate_translation, you will know it can transform the 3D translation from our pre-defined camera space to the target one, like GT Camera coordinate system you want here.

Thanks! I will look into this, I do have the camera intrinsic.

sylyt62commented, Apr 28, 2022

Indeed! I got it, thx~

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