On Wed, Dec 7, 2016 at 3:46 PM, Marek Olšák <mar...@gmail.com> wrote: > On Wed, Dec 7, 2016 at 6:00 PM, Roland Scheidegger <srol...@vmware.com> wrote: >> Am 07.12.2016 um 17:26 schrieb Marek Olšák: >>> Optimizing the CSO cache isn't exactly on the top of my list, so I >>> can't really do that right now. >>> >>> I think that varying the LOD bias is starting to be common. It's used >>> for smooth LOD transitions when loading textures during rendering. >>> Games with lots of content typically do that. This particular Batman >>> game uses UE3. >> The question of course is if they do it via sampler state or via shader >> lod bias. > > The sampler state. I saw those states. lod_bias was the only changing > variable. > >> I suppose that when these objects were designed noone thought it would >> be useful to really create sampler state with lots of different bias >> values. d3d10 of course would have the same problem (and it has limits >> on how many such objects you can create, 4096 per context) but the >> problem shifted to the app since it would have to create the objects >> explicitly - I would suspect the app there would either quantize the >> value itself, or use shader lod bias instead. > > The shader lod bias isn't a better solution though. Any LOD bias is a > modifier of the varying LOD value. For texture streaming, you want to > clamp the LOD, not shift it, thus min_lod is better. However, min_lod > is integer on ATI DX9 GPUs (not sure about the API), so DX9 games > can't use it for smooth transitions. That may explain why we are > seeing it with Wine. I guess any DX10+ and GL3+ games do use min_lod > instead of lod_bias, which means we probably get a lot of sampler > states there too. > > We could reduce the size of pipe_sampler_state a little. AMD GCN can > represent only 14 bits of lod_bias and 12 bits of min_lod and max_lod.
Looks like 13 bits of lod bias and 12 for min/max lod on G80+ GPUs: https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/nouveau/nv50/nv50_state.c#n559 Even fewer for Adreno A3xx (11 lod bias, 10 min/max lod): https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/freedreno/a3xx/a3xx.xml.h#n3102 but back up to the G80 levels for Adreno A4xx: https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/freedreno/a4xx/a4xx.xml.h#n3923 (I'm a bit surprised that GCN is 14 bits of lod bias, not 13. I guess +16 was important to them?) -ilia _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
