Interactive Media Systems, TU Wien

Terrain Geomorphing in the Vertex Shader

By Daniel Wagner


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.


D. Wagner: "Terrain Geomorphing in the Vertex Shader"; in: "Shaderx2: Shader Programming Tips & Tricks With Directx 9", issued by: Wolfgang Engel; Wordware Publishing, 2003, ISBN: 1556229887.


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