On 2015-06-06, Alan Wolfe wrote:
I am so sorry... meant to send this to myself to investigate later, my
name starts with A and my address book has this as "A" for some
reason.
Please ignore... or feel free to explain hehe.
Not really an audio topic, no. But essentially an OpenGL multisampled
texture is a texture which holds multiple samples per pixel. Such
textures are used as intermediate stages in antialiasing computations.
Essentially the multiple samples per pixel are rendered separately using
whatever rendering algorithm you happen to have chosen, but are
systematically offset from the underlying pixel grid. Eventually the
samples will be averaged together, which is a simple, easily
(embarrasingly) parallelized form of numerical integration, suitable for
the typical GPU's render pipeline.
The basic reason why you have to allocate a separate kind of render
target for multisampling is that the GPU rendering pipeline and/or the
software framework used to program it does not fully hide its internals,
or in here especially latency variance. When you multisample, the
different subpixel results arrive at slightly different times, and
aren't fully coordinated so that they could be averaged on the fly, to
land texel per texel on a normal texture patch. Instead the multiple
samples need to be stored somewhere first, in whatever order the GPU
yields them, and then after an internal synchronized barrier, run a
second time around the pipeline to average them. That calls for extra
memory for the intermediate result; GL_TEXTURE_2D_MULTISAMPLE typed
render targets reserve that extra memory and tell the graphics engine
how to use it, instead of just going with the one pixel per texel
requirement of a normal texture.
https://www.opengl.org/wiki/Multisampling
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Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
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