Heya, I have a question about vertex arrays. Say I have a vertex-array containing 1000 vertices and another array which contains indices to the vertices. I know I can draw them using glDrawElements. Now I don't want to use OpenGL's 2D culling but I'd rather use my own culling routine which uses face-normals to determine if a face is visible. This way I dont have to transform vertices which aren't visible in the first place. My question is this: does OpenGL transform all the vertices in the vertex array or only the ones that are actually given in the array with the indices? Because that way I only have to 'rebuild' my array with indices and not the array which contains the vertices. If I have to rebuild both arrays(I dont really want to do that each frame), I also have to map the new indices onto the original ones etc etc. And this way I dont think it will be faster than just transforming all vertices and just do simple 2D face culling. WickedMystic Edited by - WickedMystic on 5/6/00 4:50:15 PM Edited by - WickedMystic on 5/6/00 4:51:33 PM

Use glDrawElements() and you only have to rebuild the indices array.

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GA

Thanks to your posts I was courius to know what glDrawElements() do and how so I searched for it in my Visual C++ help but I really didn''t manage to understand how to use it. I only realised that it is involved with the use of glIndexPointer(), glNormalPointer(), glTexCoordPointer and glVertexPointer is it right ?

Could you possibly please explain me how to use it (may with a code example) ?

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Thanks

Magallo,

check these sites:

http://heron.cc.ukans.edu/ebt-bin/nph-dweb/dynaweb/SGI_Developer/OpenGL_PG/@Generic__BookTocView/7109;cd=7;td=6

and

http://www.itknowledge.com/reference/archive/1571690735/ewtoc.html


WickedMystic