blender/cycles

MoonRay is an open-source, award-winning, state-of-the-art production path tracing renderer, initially developed at DreamWorks and an active member project of the Academy Software Foundation.

Real-time GPU path tracing with an OpenUSD Hydra render delegate

c-ray is a small, simple path tracer written in C

This hardware-agnostic rendering plug-in for Blender uses accurate ray-tracing technology to produce images and animations of your scenes, and provides real-time interactive rendering and continuous adjustment of effects.

Embeddable physically based renderer

Simple Open-source Ray Tracer

LuxCore source repository

Path tracing renderer and utilities for three.js built on top of three-mesh-bvh.

The Persistence of Vision Raytracer (POV-Ray)