It renders CLOD, with geomorphs, using batched primitives. The downsides include a long preprocessing phase, and some size overhead for the disk file. But otherwise it really rocks. News 28 Jan -- Somebody just clued me in: this work has been extended with some fancy features and integrated with OpenSceneGraph. Cool stuff includes hardware mip-map generation, vertex-morphing using a Cg vertex program, etc.
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Is this during the initial mesh generation, or is there a separate algorithm which does this. It does not matter. For example, you can integrate the chunking into your mesh generation algorithm. You can even do this dynamically, so that lower levels are added dynamically e. You can also generate a high-resolution mesh from artist input or elevation measurement data and aggregate it up into all the LOD chunks at asset finalization time. Or you can mix-and-match.
It really depends on your application. Not necessarily. The tree just stores information about the geometry and how to render it. In this case would each chunk have a collision bounding box to detect the camera or player is nearby?
A very cheap and easy option is to use the distance to the centre point of the chunk and then correct it.
You know that this distance is always an underestimation: if the centre point is at distance Z, this means that half the chunk is closer than that. What we do not know however is the orientation. If we are viewing a chunk of width w edge-on, the closest bit of the chunk will be at distance Z-w. If you can live with this uncertainty you almost always can , you are done. Note that you could also correct for the viewing angle using basic trigonometry. I prefer to calculate the absolute minimum distance from the camera to the chunk to minimize artifacts.
In practice, this means doing a point-square distance test. If you can leverage your physics engine to do this then by all means do so, but you really want to think about it more in terms of "distance query" than "collision". It really depends on the design of your engine.
I would recommend keeping the leaves relatively light-weight though. Depending on your platform, just the call overhead of having a few thousand terrain-chunks perform their own update every frame can seriously impact performance.
Then you can do your GPU memory management in units of "chunks". If you have a good reason to vary the chunk geometry size, by all means go for it.
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News 28 Jan — Somebody just clued me in: As this is also grid there was no reason why not to map it to [-1, 1] coordinates and collapse it into a sphere in the shader. How this should work? It renders CLOD, with geomorphs, using batched primitives. Chunked LOD is traditionally implemented for a flat grid. Each chunk has own data for heightmap. In my opinion, cgunked usefulness is unproven.
CHUNKED LOD PDF