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From Michael Platings, "On nvidia cards mipmap generation for non-power-of-two textures with

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GL_GENERATE_MIPMAP_SGIS is very slow (over half a second for a 720*576
texture). However, glGenerateMipmapEXT() performs well (16ms for the
same texture), so I have modified the attached files to use
Texture::generateMipmap() if glGenerateMipmapEXT is supported, instead
of enabling & disabling GL_GENERATE_MIPMAP_SGIS."

Notes, from Robert Osfield, I've tested the out of the previous path using
GL_GENERATE_MIPMAP_SGIS and non power of two textures on NVidia 7800GT and
Nvidia linux drivers with the image size 720x576 and only get compile times
of 56ms, so the above half second speed looks to be a driver bug.  With
Muchael's changes the cost goes done to less than 5ms, so it's certainly 
an effective change, even given that Michael's poor expereiences with
GL_GENERATE_MIP_SGIS do look to be a driver bug.
This commit is contained in:
Robert Osfield
2008-05-28 11:19:41 +00:00
parent 20f3e74643
commit 8677c4d6d6
4 changed files with 111 additions and 46 deletions
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13
src/osg/TextureCubeMap.cpp
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@@ -344,24 +344,21 @@ void TextureCubeMap::copyTexSubImageCubeMap(State& state, int face, int xoffset,
bool hardwareMipMapOn = false;
if (needHardwareMipMap)
{
const Texture::Extensions* tex_extensions = Texture::getExtensions(contextID,true);
bool generateMipMapSupported = tex_extensions->isGenerateMipMapSupported();
hardwareMipMapOn = _useHardwareMipMapGeneration && generateMipMapSupported;
hardwareMipMapOn = isHardwareMipmapGenerationEnabled(state);
if (!hardwareMipMapOn)
{
// have to swtich off mip mapping
notify(NOTICE)<<"Warning: TextureCubeMap::copyTexImage2D(,,,,) switch of mip mapping as hardware support not available."<<std::endl;
// have to switch off mip mapping
notify(NOTICE)<<"Warning: TextureCubeMap::copyTexImage2D(,,,,) switch off mip mapping as hardware support not available."<<std::endl;
_min_filter = LINEAR;
}
}
if (hardwareMipMapOn) glTexParameteri( target, GL_GENERATE_MIPMAP_SGIS,GL_TRUE);
GenerateMipmapMode mipmapResult = mipmapBeforeTexImage(state, hardwareMipMapOn);
glCopyTexSubImage2D( target , 0, xoffset, yoffset, x, y, width, height);
if (hardwareMipMapOn) glTexParameteri( target, GL_GENERATE_MIPMAP_SGIS,GL_FALSE);
mipmapAfterTexImage(state, mipmapResult);
// inform state that this texture is the current one bound.
state.haveAppliedTextureAttribute(state.getActiveTextureUnit(), this);