DepthPass firstly:is it beneficial?
VSync is OFF for sure.
I've tested my prog on GFFX,FPS is significantly bigger,so the perfomance is as smooth as silk.
Supposedly,my ATi drivers can't deal with the situation properly,whereas NV has good-optimized early z-cull mechanizm.NV rules!
I've tested my prog on GFFX,FPS is significantly bigger,so the perfomance is as smooth as silk.
Supposedly,my ATi drivers can't deal with the situation properly,whereas NV has good-optimized early z-cull mechanizm.NV rules!
I wouldnt count on that, the GFFX is a pretty poor card when it comes to fragment shaders, as such the early z-cull might well be giving it a speed boost, where as the 9700 Mobility (which, to add to the confusion is based on the PC 9800 cards...) probably has superious shader performance and thus isnt the bottle neck in its rendering pipeline.
to help you find that bottleneck:
http://www.ati.com/developer/gdc/GDC2005_OpenGL_Performance.pdf
http://www.ati.com/developer/gdc/GDC2005_OpenGL_Performance.pdf
fwiw from memory with my shader heavy game using no half values (on my gffx) i only see ~5 % performance increase by laying down a depth pass first. so dont expect a lot with normal games
i remember an interview with carmack and he said he does a depth pass first (like you describe) in the doom3 engine.......if he does it, its gotta be good :P
Quote:Original post by Anonymous Poster
i remember an interview with carmack and he said he does a depth pass first (like you describe) in the doom3 engine.......if he does it, its gotta be good :P
No, it's not good. It's good in his specific case. Not in general. If you do a depth-pass first while you're not fillrate limited, you're going to loose performance, due to the additional transformations and bandwidth for rendering the depth-pass geometry.
Y.
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