3D engine with modern graphics
Using $5 Google Cardboard to replicate Hololens
Optical Simulation software
Tools to process and visualize scientific data and images
Virtual X-Ray Imaging Library on GPU
CIRT - CUDA Interactive Ray Tracer
Open Source Solid Modeling CAD
Highly accurate ray-tracing software system for UNIX computers
Gphoton in a simple 3d modeler and ray tracer.
A really simple (following K.I.S.S statement) ray tracing project.
VOpR - a virtual optical rail
A C++ library to easily create GUI-editable objects
Bruno's RAY Tracing Engine