- the tetrakishexahedron (vrml), basically a cube with its faces split into 4 right triangles, though it could also be thought of as a tetrahedron with each face split into 6 equal right triangles
- however, the triangles do not remain perfect right triangles after the first subdivision
- space simulator for the real planets of the solar system
- has paging and CLOD for the planet elevations and textures!
- he describes: "I have multiple-level texture and elevation blocks. The bottom level is 256x128, after that all tiles are 254x254 + a 1 pixel border. I use separate passes for the color and bumpmapping, which are loaded/generated in a background thread. Mapping is cylindrical, and all tiles are optional (you can leave out high-detail tiles at the poles, for instance)."
- "The algorithm is ROAM with a octahedron mesh. The vertex coordinates are generated from the texture coordinates. The first 5 or so levels are precomputed in a 128KB tree. Vertex coords are float, tex coords are integer."
T.
Gerstner. Multiresolution Compression and Visualization of Global Topographic
Data (.pdf)- academic paper describing a ROAM-like tessellation of the globe based on regular geographic coordinates
- oceans are depressed to preserve coastlines
- a global error values allows decimation (compression) of the whole dataset before runtime, the tree structure allows high-resolution insets (their example uses the city of Bonn)
- article describing a simple extension of ROAM to a spherical set of triangles
- Sean chose to use a triangulated cube as his starting point, but it should work as well, or better, to use any polyhedron with more faces
- has notes online describing their terrain engine:
- "The renderer is based on Thatcher Ulrich's adaptive LOD terrain
renderer featured in Gamasutra, with the following changes:
- its wrapped around a sphere
- uses double buffered vertex buffers, and reuses shared vertices when possible
- other extensions, look for "Thatcher" under "Release Notes" for full description
Organic
Vectory has pages about their
Planetary Terrain
Rendering- Based on an icosahedron with recursive subdivision
- Claims to efficiently page so that only a few MB are ever in memory
- The described algorithm is a lot like spherical ROAM, with splitting priorities and neighbor criteria for LODs
- In 2007, they published an SDK of their planetary terrain engine, closed-source but free for non-commercial use.
- a project with screenshots and demo, rendering synthetic planets with both elevation and texture LOD
- A planetary rendering demo (closed source) which shows spherical LOD, bump mapping, noise detail texture, atmospheric glow. Demo datasets of Mars and Earth.
- Apparently last updated in 2003, no current contact for author.
