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Author Topic:   Fractal Planet LOD Terrain
blackrob
New Member
posted December 21, 1999 08:37 AM            
I'm looking for any pointer or ideas anyone has about dynamic LOD Terrain integrated with fractal terrain generation ?

I want a method of generating LOD which can be used with a spherical dynamic heightfield dataset.

The basic idea is to start with a rough sphere as the base LOD and tesselate the tri's (split 1-into-4) based on the distance to the nearest of the 3 triangles vertices...

The heightmap only somes into play when nearing the surface of the planet - then the vertex height is purturbed by a fractal noise value base on the vertex location on the planet sphere.

I do high-level visibility test on each tri before I split it.

Could ROAM be adapted to work with a spherical mesh with dynamic height data ??

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LDA Seumas
unregistered
posted December 22, 1999 02:49 AM           
Check out this web site:
http://www.tanzanite.to/

They seem to have a working spherical LOD renderer that looks pretty cool.

It should be possible to use Binary Triangle Trees for a spherical world, since if you start with a Tetrahedron which is connected to itself by proper neighbor pointers, it should work to split triangles in it just as you would in a flat mesh. Then you'd just need a mapping from 3-space vertex coordinates to your 2D height field, and you should be set. When you split a tri, you would need to position its new middle of hypotenuse point in 3D according to your mapping of height map to sphere, which would be a bit more work than in 2D where you can just directly make every vertex's Y coord the raw value from the height map under it.

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-- Seumas McNally, Lead Programmer, Longbow Digital Arts

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