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uberflyx

Clip Planes for frustum culling

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Hey all, I know there are plenty frustum culling tutorials out there that all involve 'custom' planes that you have to check all your geometry against to cull, but surely the built in clip planes would work? There must be a reason why there are 6 max... and built in to the gfx card so that means they must be hardware accelerated too! But would using these be faster (as in performance wise) than implemnting your own? Obvoiusly its a heck of a lot faster to implement! Thanks

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The user clip planes are for EXTRA culling, such as making the card not render things below water, etc. Frustum culling and clipping is already occuring without setting those, but it's happening per polygon.

The software based frustum culling with custom created planes that you're worried about has a different purpose. It is intended to remove large amounts of geometry at once. Using a QuadTree and testing the corners of each level against the frustum you can eliminate 1/4 of the world, in one quick test. Moving down the levels that passed the culling check, you may be able to remove another 3/4 of the remaining geometry in another couple quick tests. You may then opt to do a quick check of an object's bounding box/sphere vs. the frustum can eliminate the entire mesh, possibly saving several expensive shader and texture changes.

Let the hardware deal with culling triangles, and have your software deal with culling entire regions of the game world, and full meshes.

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Ok I get it. I was just hoping I cold let the hardware cull all those triangles as opposed to the software having to do it...

Oh well! Back to work then.

Thanks

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