A standalone C++ 17 implementation of the sky radiance models described in the papers "A Wide Spectral Range Sky Radiance Model" and "A Fitted Radiance and Attenuation Model for Realistic Atmospheres". It contains the model library together with a simple example renderer and a GUI frontend to illustrate how to use it.
SmallUPBP is a small physically based renderer that implements the unified points, beams and paths algorithm described in the paper "Unifying points, beams, and paths in volumetric light transport simulation".
