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d000hg

Occlusion algorithms for a chunk-based heightmap

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The only occlusion testing I have so far is to recurse through the quadtree of my scene and see if the bounding boxes of the chunks intersect with the view frustrum. But I feel I should be able to check if a chunk far away is obscured by one nearby. As a first question, should I be rendering the selected chunks from nearest to furthest or vice versa? I assume reducing overdraw is good so draw furthest first? And the main question, what are some algorithms for this, can you suggest links to decent articles, and how tricky are they to implement?

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Guest Anonymous Poster
You could include some sort of static PVS data (which would need to be pregenerated)

This involves, for each chunk, calculating whether each other chunk is ever visible, and storing the result in a bitfield.

At run time you can then draw the chunks that pass the frustum test, and are visible according to the PVS data.

This is obviously only useful if your geometry remains static, but is very low processor demand at run time.

At the other end of the spectrum Yann L uses a variation on Heirarchical Occlusion Maps, an image space technique proposed by Zhang.

He uses a software renderer to produce a depth map of occluders, and then tests the bounding volumes of objects against the depths in the image to see whether the object should be submitted.

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