On Mon, Mar 29, 2010 at 4:58 PM, Nicolas Robidoux
<nicolas.robidoux@xxxxxxxxx> wrote:
> Øyvind (and all):
>
> "Long term" development question:
>
> If one was to try to optimize gegl operations which involve resampling
> (image rotation, affine and perspective transformations), do you think
> this should be done on the GPU, or should be done, outside of the GPU,
> by exploiting SSE-type operations? Any other idea?
Note that multiple other ops will eventually also be using the
resampler infrastructure, at least when using C code, among these are
displacement maps, mirrors/kaleidoscope (already exist in git),
ripples/waves ported from GIMP, mapping to and from polar coordinates
and more.
It is likely that such transformations would, at least initially reuse
the texture resampling units found in the GPU and thus probably only
provide "standard" samplers.
> It is not obvious to me that the goal should be to port "everything"
> to the GPU. Is it obvious to you?
To get the benefits offered by the GPU, at least in a scenario where
texture data has to be migrated between the systems, any operations
that does not exist on the GPU will slow down GPU based acceleration,
potentially to the degree where benefits from using the GPU will be
lost.
The approach I think makes sense for GEGL is to allow ops to opt-in to
be able to do GPU processing. With the GSOC GPU branch GPU and CPU
usage of the same GeglBuffer is transparent and tiles are
automatically migrated from RAM to texture memory and back as needed.
> What parts of GEGL are more likely to benefit from having a GPU
> version? Least likely?
Image processing algorithms that are embarassingly parallel will
benefit from having GPU versions. This at least includes compositing,
with good caching in place it might be possible to do fast gpu
recomposition of cached subgraph results from slow/non-gpuable
renderings.
/Øyvind K.
--
«The future is already here. It's just not very evenly distributed»
-- William Gibson
http://pippin.gimp.org/ http://ffii.org/
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