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Asier Murciego
08-20-2000, 05:04 AM
hello!

i'm porting my old software rendering code to openGL, and i have a little question:
¿which is the fastes way to render triangles/polys with opengL?

1.calling glBegin(GL_TRIANGLES) and drawing all the tris

2.using vertex arrays

3.usign interleaved vertex arrays

thx!

Bob
08-20-2000, 06:18 AM
Well, it depends on how you store your data. If you store your data in such a way that you can use vertex arrays, then use it. You don't have to call OpenGL-functions for each vertex/normal/texturecoordinate and so on, so this is a way of gaining speed.

If you store all polygons like a linked list of polygons, or an array of polygons (where each polygonstructure holds three vertices, a normal, color and so on, for example), then the best way to draw might be using glBegin/glEnd pairs.

And interleaved arrays is almost the same as "regular" vertex arrays. Use this if it's suitable.

skw|d
08-22-2000, 08:03 AM
The problem with calling a lot of glFoo() functions is that each function call creates a bit of overhead (the registers and return ip must be pushed on the stack). The solution is to use display lists, one call of the display list will batch execute a set of GL functions.

Sometimes a display list cannot be used, say you have dynamicly changing color values from dynamic lighting. In this case it would be optimal to use arrays.

/skw|d