On Thu, 3 Nov 2011 10:16:06 +0800, Yuanhan Liu <yuanhan....@linux.intel.com> wrote: > On Wed, Nov 02, 2011 at 02:18:46PM -0700, Eric Anholt wrote: > > On Wed, 2 Nov 2011 11:12:07 +0800, Yuanhan Liu > > <yuanhan....@linux.intel.com> wrote: > > > On Tue, Nov 01, 2011 at 05:57:36PM +0800, Yuanhan Liu wrote: > > > > According to bspec, MIPCnt(was set to intelObj->_MaxLevel) was used for > > > > min/mag filter mode determination. For a normal case with no mipmap like > > > > this: > > > > > > > > glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); > > > > glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); > > > > > > > > hardware would always choose mag filter(GL_LINEAR) here since MIPCnt was > > > > set to 0 zero, then would make LOD be zero. Then according the formula: > > > > MagMode = (LOD - Base <= 0) > > > > > > Here are some more comments about this: LOD is a pre-computed value. if > > > preClamp is enabled, then LOD would be: > > > LOD = min(min(MIPCnt, MAX_LOD), LOD); > > > > > > So, if MIPCnt was set to 0, and preClamp was enabled, then the _final_ > > > LOD would be 0, and hardware choose mag filter. > > > > > > Thoughts? > > > > It took me a long time to understand what you were trying to fix here. > > Sorry for that :( > > > The story I've worked out is: > > > > "We can't optimize out uploading the other mipmap levels for > > non-mipmapped filtering modes if the min filter is not the same as the > > mag filter. This is because the min/mag decision is based on the > > computed LOD of the sample, and if we clamp the LOD to BaseLevel by not > > including the other levels, it will always choose the mag filter even if > > minification should have occurred. > > Yes. > > > See page FINISHME: citation of PRM." > > Sorry, what does this mean?
If you're going to make a reference to the spec, if possible please quote the exact section from the public PRM, so the next person to find it has a nice reference to read up on. > Yeah, I saw that. While thinking about this issue, I thought another > patch to fix this issue. It's somehow against with the Bspec: preclamp > should be enabled for OpenGL driver. > > Anyway, here is the patch, and I'd like to know what's your thoughts. I think I liked the previous one more. While I couldn't come up with a testcase for how this one would break, I still think just disabling the minor optimization in this weird case is more obviously correct than this change.
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