DTU's coordinate system convention

[raynehe]

Hi, thanks for the wonferful work!

I'm using a NeRF synthetic dataset, which follows OpenGL coordinate system convention (x-axis to the right, y-axis upward, and z-axis backward along the camera’s focal axis). When I apply the dataset to VolSDF directly, the computed ray_dir is incorrect.

I think the problem is in the rotation matrix, DTU/BlendedMVs might follow a different convention. But I couldn't find anything about the coordinate system convention of DTU dataset, do you know about this?

I also mention this in #12 .

Thank you very much!