Geomipmapping or geometrical mipmapping is a real-time block-based
terrain rendering algorithm developed by
W.H. de Boer in 2000 that aims to reduce
CPU processing time which is a common bottleneck in
level of detail approaches to terrain rendering.
Prior to geomipmapping, techniques such as
quadtree rendering were used to divide the terrain into square tiles created by binary division with quadratically diminishing size. The subdivision step is typically performed on the CPU which creates a bottleneck as geometry commands are buffered to the
GPU
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...
. Unlike quadtrees which send 1x1 polygon units to the GPU, to reduce the CPU processing time geomipmapping divides the terrain into grid-based tiles which are themselves regularly subdivided. Typically, a fixed number of
vertex buffer objects (VBOs) are stored on the GPU at different grid resolutions, such as 10x10 and 20x20, and then placed at major terrain regions selectively chosen by the CPU. A vertex shader is then used to reposition the vertices for a given VBO, all on the GPU. Overall, this results in a major reduction in CPU processing, and reduced CPU-to-GPU bandwidth as the GPU then performs most of the work.
Geoclipmaps and
GPU raycasting are two other modern alternatives to geomipmapping for interactive rendering of terrain.
See also
*
ROAM
Real-time optimally adapting mesh (ROAM) is a continuous level of detail algorithm that optimizes terrain meshes. On modern computers, sometimes it is more effective to send a small amount of unneeded polygons to the GPU, rather than burden the C ...
References
* de Boer, W.H., ''Fast Terrain Rendering using Geometrical Mipmapping'', in flipCode featured articles, October 2000. Available at https://www.flipcode.com/archives/article_geomipmaps.pdf
Computer graphics algorithms
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