My renderer for learning

All tiny third-part libraries, including filesystem, halton, pcg32, stb_images, tinyformat, tinyobjloader and pugixml, are in the src/ext/ folder.
Except that, Rainbow need embree3, tbb and openvdb.
If you don't know how to add the three libraries, I recommend you use some package manager like vcpkg.

 > vcpkg install embree3 tbb openvdb : x64-windows  
 > vcpkg integrate install 

Now I just test building it on Windows.
Please build as x64 platform like

 > mkdir build
 > cd build
 > cmake -G "Visual Studio 15 2017 Win64" ..

Or use ./setup_builds.bat.

Project Website

Homogeneous Medium(BDPT WIP)

Heterogeneous Medium
Rendered using volumetric pathtracing.