Stencil Preformance
Author
So I was hacking my way through Lesson 26 and everything is wokring fine except the preformance is horrible. As soon as I disable the stencil buffer, though, it works fine. I double checked everything, I'm running in 32-bit mode with a res of 1280x1024, a depth buffer of 16 and stencil buffer of 8. I've cleared the stencil buffer in both InitGL () and DrawGLScene. I replicated these settings using the demo code, and it runs fine. I've got a 1.7ghz P4 with a GeForce 2.
You need a 24 bits depth buffer. With only 16 bits you'll get stencil buffer emulation in software, hence why it's slow.
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If you're running in a window, that might be it. On a GF2 I owned, whenever the stencil buffer was used in a windowed application, it was incredibly slow. When I switched to fullscreen, it suddenly ran at proper speeds.
I haven't ever had any performance hit using the stencil buffer. I may be wrong, but depending on the application, I think you could do a 1 bit stencil buffer. I only use it for shadows. I use a matrix to flatten the shadows to the plane, then draw the objects normal, the only difference is that I make the plane 0.1 above the original plane, I can't tell the defference and using the stencil buffer, you still draw only where the plane is. For this, I only use a 1 bit stencil buffer because it is only a yes-no whether to draw this pixel or not. I don't count the repeats or anything like that so I don't think anything larger is needed.
Author
Yeah, I'm using it it to do reflections (from Nehe tutorial 26). I originaly had the stencil buffer set to 1, but then I was searching for a fix to my problem from previous threads and in one(forget which) and someone said to increase the stencil buffer to 8. That obviously didn't help, but whatever. Thanks anyway.
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