We use  doxygen for source code and API documentation. It is integrated into Trac, just click the Doxygen button in the menu above.

In addition to doxygen there is a separate section of the Wiki for longer, conceptual descriptions and explanations as well as tutorials.

They are ordered and put in a sensible order on wiki:Doc/DevGuideFull, but you can also see the individual pages:

• DevGuide/Fields Fields
• DevGuide/StageRendering Overview
• DevGuide/BaseTypes Base Types
• DevGuide/BaseMath Base Math
• DevGuide/OcclusionCulling Occlusion Culling
• DevGuide/Statistics Statistics
• DevGuide/Geometry Geometry
• DevGuide/ScreenLOD ScreenLOD
• DevGuide/Logging Logging