The content of this section exists only to describe, in general, the three main components required for three-dimensional modelling and rendering with a Linux-based system.
A graphics library consists of the most basic tools used for manipulating graphical images. Think of all the things needed to build a house: wiring, plumbing, wood, bricks, and such. The graphics library can be thought of as not these items, but rather the tools used create such items. After all, wire, metal tubes, planks, and bricks don't magically appear; rather they are created and formed as entities unto themselves. On a similar note, graphics don't magically appear on the screen -- typically they consist of lower-level graphics primatives (lines, rectangles, and individual pixels, for example).
So the graphics library, then, can be thought of as the low-level graphics primatives used to build more complex objects (spheres, boxes, complex polygons, etc.). Those complex objects are then used to build even more complicated shapes and figures.
The graphics library installed was the freeware implementation of OpenGL called Mesa.
Since the graphics renderer is, ideally, completely hidden from the end-user, we'll deal with that last (besides which, modelling is the next logical step in keeping with my house-building analogy). However, when it comes to the actual installation, a graphics modeller relies on the renderer already being installed.
If the graphics library is akin to the tools used to build the tools used to build a house (!), then graphics modellers can be thought of as the tools used to build the blueprints for the house -- sophisticated blueprints, as modellers let you dictate exactly where the wiring, plumbing, wood panels, bricks, and forth are supposed to go. Furthermore, they let you pick the style of panelling and the colour of the bricks you desire.
The graphics modeller installed was the freeware package called The Mops, which produces RenderMan-compatible files.
In keeping with the house-building analogy, the graphics renderer is then the construction workers. Once you have the blueprints and materials ready to go, you need something to actually build the house so it appears how it was designed. The graphics renderer is given information (i.e., the blueprints in the form of a RenderMan-compatible file, or equivalent) from the modeller to produce the final result.
Just as the graphics modeller needs the graphics renderer before it can be installed, the renderer relies on the graphics library being installed beforehand.
The graphics renderer installed was the Blue Moon Rendering Toolkit which uses RenderMan files.