ps2tiffs extracts the sampled images from a PostScript document. It is not a PostScript renderer. ps2tiffs is a system where the grazer feeds on the output of a PostScript interpreter whose image operators have been replaced by special data-hijacking functions. This has the benefit of allowing the extraction of images regardless of how they have been encoded, formatted, scaled, or squished by the app which generated the PostScript document. It outputs greyscale, RGB, and CMYK TIFFs.
s3d is an XML schema for 3d scenes, objects, and so forth (intended primarily but not exclusively for computer games). The problem is that often as a games developer you need to work with many 3d editing tools and rendering engines, and there should be an easy and portable way to move objects, levels, etc. around. By having a common intermediate file format, you only need to write one exporter per tool and one importer per graphics engine. Also, you can develop generic tools which are not tied to any particular engine.
Grlib is an implementation of generative grammars and turtle graphics. The grammars (Lindenmayer systems) are used to produce descriptions of three dimensional objects, and the turtle is used to display them (i.e., generate images in several forms, such as bitmap, PostScript, or OpenGL).