NOX Renderer!

LuxRender is a physically based and unbiased rendering engine. Based on state of the art algorithms, LuxRender simulates the flow of light according to physical equations, thus producing realistic images of photographic quality.

The Persistence of Vision Raytracer is a high-quality, totally free tool for creating stunning three-dimensional graphics. It is available in official versions for Windows, Mac OS/Mac OS X and i86 Linux. The source code is available for those wanting to do their own ports.

Clara.io is a full-featured cloud-based 3D modeling, animation and rendering software tool that runs in your web browser.

PhotoRealistic RenderMan, or PRMan for short, is a proprietary photorealistic RenderMan-compliant renderer.

KeyShot is an interactive raytracing and global illumination program developed by Luxion for both PC and Mac that breaks down the complexity of creating photographic images from 3D models.

Powerful, feature-rich and fast standalone raytracing renderer.

A free Terrain Synthesizer and RendererPicogen is an outdoor ray tracing system, a free Terrain Synthesizer and Renderer targeting large-scale terrain with realistic day/night-illumination and detailed plant populations.

appleseed is a modern, open source, physically-based rendering engine designed to produce photorealistic images, animations and visual effects. It provides individuals and small studios with an efficient, reliable suite of tools built on robust foundations and open technologies.

fryrender is the physically-based light simulator developed by RandomControl. It is a photo-realistic render engine where all the elements involved in the generation of the final image (materials, lights and cameras) are based on physically accurate models.

Tungsten is a physically based renderer I originally wrote in early 2014 for the Image Synthesis Rendering Competition at ETH, where it won 1st place with the image pictured above. It is intended for offline rendering in graphics research and is still in development, at least whenever I find the time. It lives on Github.

Sunflow is an open source rendering system for photo-realistic image synthesis. It is written in Java and built around a flexible ray tracing core and an extensible object-oriented design. It was created as a framework for experimenting with global illumination algorithms and new surface shading models.Current Features:

Indigo Renderer is an unbiased, physically based and photorealistic renderer which simulates the physics of light to achieve near-perfect image realism. With an advanced physical camera model, a super-realistic materials system and the ability to simulate complex lighting situations through Metropolis Light Transport, Indigo Renderer is capable of producing the highest levels of realism demanded by architectural and product visualization.

Pixie is an open source RenderMan renderer for generating photorealistic images. You can compile Pixie on Windows (using Visual Studio 2005), Linux and on OSX (using XCode or unix style configure script).