In the middle of building the rendering and composition stack for Intel's Project Alloy, I elected to take a brief vacation from working on a 11.11ms VR render budget to build this project, a toy Monte Carlo unidirectional path tracer. It features a multi-threaded render loop, tent-filtered jittered sampling scheme, and a variety of geometric primitives. Bugs are highly likely in this code!
Various projects were studied during the development of this, notably Benedikt Bitterli's Tungsten, Fabrizio Duroni's SCLT, and PBRTv3. Other educational sources are listed in the header of main.cpp.