MacOS X, Linux (i386) and Windows. Freeware. Source code is available.
Do you know the excellent freeware raytracer Persistence of Vision (POV-Ray)? It takes text files that describe three-dimensional scenes and turns them into high-quality images.
The biggest disadvantage of high-quality 3D graphics is that it takes a lot of processing power. Rendering a POV-Ray image can take anywhere from five minutes to several hours.
VOP is intended to read the same files as POV-Ray. However, the focus is on speed instead of image quality. By using completely different techniques to create low-quality images quickly, VOP can give you a quick "vision" of what you will get when you use POV-Ray to render your scene. For example, VOP doesn't even attempt to render nice surface textures: all objects look like they are made of uniformly colored plastic.
For now, VOP only supports the most common of POV-Ray's object types.
Please note that VOP is not created, maintained or endorsed in any way by the POV-Ray Team. It does not share any source code with POV-Ray. The only thing the two programs have in common is that VOP tries to read POV-Ray's file format. Do not bother the POV-Ray Team with questions related to VOP.
The following image has been rendered by VOP:
It took 9 seconds on my PentiumII/300 to display this image - after that, the camera can move around at 28 frames per second (!).
The same scene file produces a much nicer image when run through POV-Ray, but it takes much longer:
This image took 72 seconds to render in POV-Ray. If I want to render an animation with the camera moving about, it would still take 72 seconds for every frame.