Hi, thanks first for the amazing tools. I am currently trying to use grid_sample() to sample colors from a texture image to be the color of vertices from a 3D .obj model (part of a rendering process), and then the color is used to compute loss and gradients are expected to back-propagate to the texture image. However, in the experiment gradients on the texture image are all zero.
To find out the reason, I replace the grid with an “ordered” one, like those generated by affine_grid(), then the gradients are non-zero. Thus, I am wondering if this is because the original grid is defined by the UV coordinates corresponding to each vertice in the 3D model, and thus there is no regularity in it. I would appreciate if anyone could tell me whether there are certain constraints on defining the grid, or if there may be other reasons that make the grad zero.
Many thanks!!