[Bf-committers] Compositing output while editing

[Lukas Tönne]

After some discussion on IRC i made a quick simple patch to avoid full
composite recalc after each node edit:

http://www.pasteall.org/40351/diff

Without this all potential output nodes are enabled both in preview
and full composite executions. The patch separates this, doing preview
and viewer calculation only on preview runs (i.e. automatic updates
after tweaking nodes) while composite output and file output nodes
only run on full composite executions (pressing F12). It already seems
to improve editing quite a bit, only issue it seems is that the
previous render result and previews are discarded in both cases,
leaving either one un-calculated after updating the other (F12 ->
previews get lost, node edit -> render result gets lost).

Some other possible improvements discussed:

1) Restriced and/or scaled viewer image: Sergey has already been
working on a composite border feature AFAIK, for reducing the amount
of work done in viewer updates

2) Re-use buffers calculated by viewers and composite output
respectively. This will require a working cache system so the buffers
don't get lost each time between updates. I posted a prerequisite
patch a while ago, this should allow the compositor cache to further
reduce executions to outdated parts:
http://lists.blender.org/pipermail/bf-committers/2013-January/039013.html

3) Allow recomposite without requiring full render every time (as
happens on F12). I think the current solution involves making a
"compositing scene" with no mesh data and only a compositing setup
using images, but that's a bit of a workaround it seems. It shouldn't
be hard to make an operator that only executes the compositor without
rendering (the opposite, render without composite, can be done simply
by disabling Compositing in Post Processing panel). There might even
be a feature for this i don't know about, since Sebastian said it
existed in 2.49 ...

On Sat, Mar 9, 2013 at 2:58 PM, Sergey Sharybin <sergey.vfx at gmail.com> wrote:
> Hi,
>
> Noticed that currently compositor output node will be fully recalculated
> every time you're editing compositor node tree. This adds quite enough of
> CPU consumption and only benefit from this is having Render Result image
> up-to-date.
>
> Is it something indeed expected by artists? From what i've noticed during
> Mango and some post-mango artists feedback -- they're usually disconnecting
> compo output node to make compositing faster. But this often leads to
> troubles when you forget to connect node back, send 12hrs shot to the farm
> and.. Well, nothing fun out of this.
>
> So, the question is: is it even helpful to have Render Result updating
> every time you're editing the tree? And if so, what about:
>
> - Making it a compositor option to ignore compo output while editing
> - Making it possible to mute compo output node, which will mean it's
> ignored while editing (but not while rendering)
>
> --
> With best regards, Sergey Sharybin
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