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Julio

overdraw stats?

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Julio    116
I know that when you render objects in the foreground before objects in the background it''s slower than depth sorting them and then rendering. does anybody know of any statistics for this as far as OpenGL (or I guess Direc3D aswell for that matter)? how much does it actually slow down? thanks, Joe HHSDrum@yahoo.com Polarisoft Home Page

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zedzeek    528
i think u got that around the wrong way.
of course this varies per card (old voodoos make no difference) + per scene but for solid polygons u should always try to draw the ones closest to the camera first, this''ll result in a 0-20% speedup.

http://members.xoom.com/myBollux

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Guest Anonymous Poster   
Guest Anonymous Poster
zedzeek is correct. I thought I''d just give the reason for those interested. Assuming you are using a z-buffer to resolve overdraw issues it''s faster to render the closest polygons first, and then draw polygons further away. Because then, chances are that a far away polygon will be obscured and pixels can be discarded if they fail the z-test. If a pixel passes the z-test it also has to be written to the screenbuffer etc... (perhaps lit and stuff too, depending on when lighting occurs).

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