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mipmapping with FBO's

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Has anyone here seen a huge slow down in FPS when using glGenerateMipmapEXT? I am not happy with the fps drop when I use mipmaps with my FBO's. Anyone else seen this behavior? and if not what are you doing that I am not! :) Thanks

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I'm not sure what I'm doing that you're not doing, but I've never seen this behavior. In fact, my code speeds up when I use glGenerateMipmapEXT (as it should, because mipmapped textures fit into cache better). If I could gander a guess, I'd say you might not be using a square power of two framebuffer.

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void FBO::ShutdownBuffer(void)
{
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

if(mipmapping)
{
for(unsigned int x = 0; x < numColorTextures; x++)
{
glBindTexture(texture_target, colortextures[x]);
glGenerateMipmapEXT(texture_target);
}

glBindTexture(texture_target, depthtexture);
glGenerateMipmapEXT(texture_target);
}
}




thats the rendering code... and the sizes are 1024x1024

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u should see a slowdown, so how much of a slowdown (5-20% i expect is normal) how much are u seeing? is it major eg ~10x if so post your texture type

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well I drop from 40-45 to 0-4 fps...

settings
if I use GL_LINEAR_MIPMAP_LINEAR or GL_NEAREST_MIPMAP_LINEAR no difference.
GL_LINEAR is GL_TEXTURE_MAG_FILTER. So I am unsure what is going on.

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Guest Anonymous Poster
Sounds like a drop to software. Are you sure your card supports the extension? It might be software emulated for some bizarre reason..

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Quote:
Original post by MARS_999
well I drop from 40-45 to 0-4 fps...


ok, thats a hell of a hit...

How about trying it sans mipmaps first, then add colour mipmap generation back, one at a time, then remove and do depth only and finally put them all back and see where your fps bombs out.

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