[Bf-cycles] GPU future

Brecht Van Lommel brechtvanlommel at pandora.be
Sun Dec 9 12:37:46 CET 2012


On Sun, Dec 9, 2012 at 11:46 AM, David Bucciarelli <davibu at interfree.it> wrote:
> Il 09/12/2012 05:01, storm ha scritto:
>> But selected hardware (AMD :) )can have limits, and force to use
>> hybrid model, as Luxrender show.
> I'm not aware of any particular AMD hardware limitation. A HD7970 is a
> lot faster than a GTX680 in GPU rendering.

My understanding is that AMD hardware must inline all functions, while
I know NVidia hardware supports actual function calls and dynamically
loaded modules. Inlining everything limits the complexity of the
kernels you can run.

> LuxRender uses hybrid rendering because the hundred of thousands of
> lines of Lux code will never runs on any GPUs. For the same reason, it
> very unlikely to ever see OSL in any GPU renderer.
> If you want 99% of features you have on the CPU, you have to use hybrid
> rendering. If you want to run at full GPUs speed, you have to accept
> many limitations. LuxRender has an hybrid renderer for the first case,
> and now a SLG renderer for the second.

The way I see it is that fundamentally the GPU has few limitations,
but actually implementing all features on them is just too much work.
Implementing something like OSL on the GPU is possible but I don't
have the time for it.

So anyway, for Cycles this means I'll try to keep things running on
the GPU as much as possible, in principle SSS/Hair/Volumetrics are
possible but I'm not making any promises. OSL is unlikely to run on
the GPU anytime soon.


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