[Bf-cycles] Cycles geometry synchronization

[Brecht Van Lommel]

Most of the time is usually evaluating modifiers, particularly for
subdivision surfaces or particles. Once Blender has evaluated those
things the copying itself isn't that slow from what I've analyzed, and
I'm sure other render engines have similar steps, just under a
different name?

What we could optimize here is doing multithreaded sync(this relies on
the multithreaded depsgraph project), or doing our own subdivision in
Cycles. If it's particularly slow without modifiers that would be
interesting to investigate and see how it could be made faster.

It doesn't have anything to do with how deeply Cycles is integrated
really, just stuff that could be worked on.

On Sat, Jul 13, 2013 at 12:50 AM, Matthew Heimlich
<matt.heimlich at gmail.com> wrote:
> Hey all,
>
> I was thinking about the long sync step when rendering with Cycles and had a
> couple of questions. As far as I can tell, external renderers in other 3D
> packages done require this step. Is this because the other
> renderers/packages directly use the geometry data already in memory directly
> from the 3D package? If so, this makes me wonder if this step is a due to a
> limitation of Cycles not being as deeply integrated with Blender as it could
> be (if I recall it was originally intended to operate as a standalone that
> could work with other packages as well) or if there is a limitation with
> Blender itself in terms of the data it makes available to external programs.
>
> As I understand it, the process now is:
>
> Start rendering process ->
> Copy geometry data from Blender to a Cycles buffer ->
> Build BVH based on this data ->
> Begin intersection tests
>
> With the geometry copy being a very time consuming step, especially for
> complex scenes. Please correct me if I'm wrong anywhere. Just trying to
> continue wrapping my head around the inner workings of Cycles as a whole.
>
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