Missing `_raytracing` CUDA extension prevents Stage 2 training

[karthikaf]

When attempting to run Stage 2 (material learning) training, the code fails with ModuleNotFoundError: No module named '_raytracing'. The _raytracing CUDA extension source files appear to be missing from the repository.

Error Message

Traceback (most recent call last):
  File "/home/user/NeP/nep/ns/pipeline.py", line 49, in __init__
    from nep import raytracing
  File "/home/user/NeP/nep/raytracing/__init__.py", line 1, in <module>
    from .raytracer import RayTracer
  File "/home/user/NeP/nep/raytracing/raytracer.py", line 6, in <module>
    import _raytracing as _backend
ModuleNotFoundError: No module named '_raytracing'

Environment

• OS: Ubuntu Linux
• Python: 3.10
• PyTorch: 2.9.1 (cu128)
• CUDA: 12.0
• Nerfstudio: 0.3.4

Analysis

The nep/raytracing/raytracer.py file imports _raytracing as _backend, which is expected to be a compiled CUDA extension. However, the repository only contains:

- nep/raytracing/init.py
- nep/raytracing/raytracer.py

No .cpp, .cu, or setup.py files for building the extension are included.

I attempted to use ashawkey/raytracing as an alternative, but it's incompatible with PyTorch 2.x due to API changes.

Request

Could you please:

1. Add the missing _raytracing CUDA extension source files to the repository, or
2. Provide installation instructions for the raytracing module, or
3. Indicate which external package provides this module?

Additional Notes

I also encountered a missing nero.utils.draw_utils import in the updated nf.py file. Is the nero package available somewhere?

Thank you for your help!