Terrain Geomorphing in the Vertex Shader

Terrain rendering has heretofore been computed by a CPU and rendered by a combination of CPU and GPU. It is possible to implement a fast terrain renderer which works optimally with current 3D hardware. This is done by using geo-mipmapping which splits the terrain into a set of smaller meshes called patches. Each patch is triangulated view-dependently into one single triangle strip. Special care is taken to avoid gaps and t-vertices between neighboring patches. An arbitrary number of textures can be applied to the terrain which are combined using multiple alpha-blended rendering passes. Since the terrain’s triangulation changes over time, vertex normals cannot be used for lighting. Instead a pre-calculated lightmap is used. In order to reduce popping when a patch switches between two tessellation levels geo-morphing is implemented. As will be pointed out later, this splitting of the terrain into small patches allows some very helpful optimizations.