The ambient, diffuse and specular colors ([r, g, b], 0 to 1) of the
window's light (OpenFrames' defaults: 0.2 gray, white, none). The
window's light is used while no frame of the scene has a light source
(set_light_source_enabled).
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.