How can I get a camera pose for the input image?

[AlbertHuyb]

Thanks for the nice work!

I want to get the camera pose for the input image. After I read some of the code, I noticed that you utilized the following code in provider.py to render image exactly at the input camera pose (here):

        if not self.training:
            if is_face or can_pose:
                mvp = projection @ torch.inverse(poses.cpu()).to(self.device)
            else:
                mvp = torch.inverse(poses.cpu()).to(self.device)
                mvp[0, 2, 3] = 0.
                TO_WORLD = np.eye(
                    4,
                    dtype=np.float32,
                )
                TO_WORLD[2,2] = -1
                TO_WORLD[1,1] = -1
                TO_WORLD = mvp.new_tensor(TO_WORLD)
                mvp = TO_WORLD @ mvp

I wonder why these code lines work, because the resulting mvp matrix does not consider the projection matrix. And I don't understand why we should set mvp[0, 2, 3] to zero.

Moreover, I'd like to know how could I compute a camera pose pose_gt such that the corresponding mvp matrix could computed by

mvp = projection @ torch.inverse(pose_gt).to(self.device)

Looking forward to your response. Thanks!