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Sub-division surfaces and tesselation algorithms

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Hello, I''ve been learning alot about sub-division surfaces and how they are the choice method when modeling. I was wondering if it is possible and if so, is there any algorithms that are out that can reverse the effect. In other words, go from a very detailed object and continue going less and less detailed until you reach a rather low polygon primitive looking shape. How fast are these algorithms? Are there dynamic in that they can go from high detail to any low detail using a scaler? If you know the answers to any of these questions or you know where I could find some more information on such topics, please let me know. Thanks alot, Salec

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Yes, these meshes are called progressive meshes.

DirectX supports them. They are a little fiddley to set up but once you have they are great.

I am sure if you serch on that you will find some matches.

D.V.

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How about in OpenGL? I doubt openGL supports them directly, but I''m sure there has to be some algorithms I could run on a vertex array or BSP tree.

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Yes I have come across two different algorithms, both use a weighting technique to determine which vertex is removed.

Unfortunately I do not have the references with me (I am at my *real* job) so I can''t give them to you.

I will look them up when I get home (8 hours time) and post them here.



D.V.

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Sorry, for the delay. Unfortunately I can''t find those links anywhere.

I just recently cleaned all the bumf off my development machine and it appears I was a little to enthusiastic.

D.V.

Carpe Diem

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This area is generally refered to as continuous level of detail (CLOD). Progressive meshes is the first step, yuo also need to mush texture coorindinates and normals.

"3D Game Engine Design" describes the "Garland and Heckbert" method. Each pass you eliminate a small number of vertices and merge the adjacent triangles. The new mesh is placed in a depth sorted list which is used to pick which model to display at run-time.



Magmai Kai Holmlor
- Not For Rent

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