Terragen 4 User Guide Part 2: Fundamental Rendering and Shader Concepts
This part of the User Guide explains some of the fundamental concepts used for rendering and by shaders in Terragen 2.
The Displacement page explains displacementLiterally, to change the position of something. In graphics terminology to displace a surface is to modify its geometric (3D) structure using reference data of some kind. For example, a grayscale image might be taken as input, with black areas indicating no displacement of the surface, and white indicating maximum displacement. In Terragen 2 displacement is used to create all terrain by taking heightfield or procedural data as input and using it to displace the normally flat sphere of the planet..
This Global Illumination|document from the Terragen 2 Reference explains global illumination (GI) and how it works in TG.
This page talks about what procedural data is, how TG uses it and how it compares to static data.
This page discusses the two rendering methods TG uses - micropolygon rendering and raytracing.
This page explains the translucency effect available in several shaders.