Picogen!

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.

Terragen is a scenery generator, created with the goal of generating photorealistic landscape images and animations.It is already capable of near-photorealistic results for professional landscape visualisation, special effects, art and recreation. Terragen has been used in a variety of commercial applications including film, television and music videos, games and multimedia, books, magazines and print advertisements.

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.

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

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.

World Machine is a proven terrain generation solution for artists, game developers, visual effects studios and other visualization professionals

Bryce is an award winning, fun, feature-packed 3D modeling and animation package designed to allow new users to quickly create and render stunning 3D environments. Bryce combines exceptional power with an innovative interface for incredible ease of use. Add wildlife, people, props and more to your scenes via the DAZ|Studio character plug-in in addition to terrain, water, sky, rocks, clouds, fog, vegetation, and architecture for which Bryce has long been the standard.

NOX Renderer is a rendering software based on unbiased methods.

Nem's Mega 3D Terrain Generator is a relatively new terrain generator that takes a step in a completely different direction. Unlike traditional generators where the user must depend solely on the generators generation abilities, this generator gives its users complete 3D control over what their terrain looks like. Users start off with a flat piece of landscape, then add to it with one, or a combination of many powerful generation options. They then have several tools at their disposal to literally grab the terrain and pull it as they want it. It can be saved as .tgm, .map, .t3d, .rmf, or .vmf »

Adobe Dimension CC (formerly Project Felix) is the 3D design tool made for graphic designers. With extensive integration with Adobe Stock, you can easily composite 2D and 3D assets to build product shots, scene visualizations, and abstract art. You can preview your design as you go, experiment and edit your ideas without having to render a final image to see your work. You can also enlarge the preview window to see details up close. When you’re ready, render your design into a high-quality asset you can save and then open in Adobe Photoshop CC to refine further. »

Octane Render is the world's first GPU based, un-biased, physically based renderer. What does that mean? It uses the video card in your computer to render photorealistic results fast...really fast. This allows the user to create stunning works in a fraction of the time of traditional CPU based renderers.

Geomorph is a height field generator and editor for the Linux operating system.

3Delight is a fast, high quality, RenderMan®-compliant renderer designed to produce photo-realistic images in demanding production environments. The renderer was introduced to the public in the year 2000 after being used for more than a year as the sole renderer in a sister production company. It is now widely used and earning a reputation as a benchmark in rendering technology.

MiniLight is a minimal global illumination renderer. It is primarily an exercise in simplicity. But that makes it a good base and benchmark (in some sense) for development and experimentation. And it just might be the neatest renderer around (on average, about 650 lines). There are translations into several programming languages.