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authorRoland Scheidegger <[email protected]>2013-10-18 20:52:26 +0200
committerRoland Scheidegger <[email protected]>2013-10-21 15:42:04 +0200
commit3bdd1074e1e85faa73ba927dee1547d956f6144f (patch)
treedd7e72cb27bcc6bd6184614e2dc3b8898dcab1c3 /src/gallium/drivers/llvmpipe/lp_context.h
parent21a57f9040b1688e6501509c88c79c2d277c8b1e (diff)
gallivm: implement seamless cube filtering
For seamless cube filtering it is necessary to determine new faces and new coords per sample. The logic for this is _seriously_ complex (what needs to happen is very "asymmetric" wrt face, x/y under/overflow), further complicated by the fact that if the 4 samples are in a corner (meaning we only have actually 3 samples, and all 3 are on different faces) then falling off the edge is happening _both_ on x and y axis simultaneously. There was a noticeable performance hit in mesa's cubemap demo when seamless filtering was forced on (just below 10 percent or so in a debug build, when disabling all filtering hacks, otherwise it would probably be a bit more) and when always doing the logic, hence use a branch which it only does it if any of the pixels in a quad (or in two quads) actually hit this. With that there was no measurable performance hit in the cubemap demo (neither in a debug nor release buidl), but this will vary (cubemap demo very rarely hits edges). Might also be different on other cpus, as this forces SoA sampling path which potentially can be quite a bit slower. Note that as for corners, this code gets all the 3 samples which actually exist right, and the 4th texel will simply be the same as one of the others, meaning that filter weights will be a bit wrong. This however should be enough for full OpenGL (but not d3d10) compliance. Reviewed-by: Jose Fonseca <[email protected]> Reviewed-by: Brian Paul <[email protected]>
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