[Mesa-dev] [PATCH 2/4] gallium: extend resource_resolve to accommodate BlitFramebuffer

Roland Scheidegger sroland at vmware.com
Mon Jul 25 16:49:47 PDT 2011

(Strange thought sent that before - mail client going crazy...)

> Resolving color buffers is pretty well defined (for standard msaa at
> least). I have no idea how that's supposed to be defined for depth
> and stencil values. Frankly I'm not sure what glBlitFramebuffer is
> supposed to do here, maybe it's defined somewhere but even applying
> the term "resolve" to a depth buffer seems very iffy. At the very
> least it needs to be documented in the gallium docs what "resolving"
> a depth/stencil buffer really means.

Hmm actually it must be like ReadPixels. So it is "recommended" that implementations just use the centermost sample, but this is not required. In particular "any function using depth/stencil values" is valid.
Taking this to the extreme, this means just returning 0 is valid (f = 0*sample0 + 0*sample1...) though probably not recommended...
Averaging would be allowed as would be any other crazy stuff. In any case calling this step, whatever it does, "resolve" seems abusive with results possibly quite implementation dependent. I have no idea what nv50 does here though I guess given the loose definition it should certainly fit the requirements.


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