viewdirs vs direction in cast_rays

[bring728]

Hi! Thank you for your wonderful work.

I have a question about

zipnerf-pytorch/internal/render.py

Line 146 in 4de3d21

basis_matrix = torch.stack([ortho1, ortho2, directions], dim=-1)

this function. Why do you use the directions vector instead of the normalized vector viewdir? I guess basis_matrix should be a rotation matrix and each column should be a normalized vector. So shouldn't I use viewdir instead of directions?