[Bf-cycles] Progressive Animation Rendering

[Brecht Van Lommel]

Hi Greg,

On Wed, Jul 31, 2013 at 7:48 PM, Greg Zaal <gregzzmail at gmail.com> wrote:
> I'd like to know if there's any interest in this sort of thing, and if
> so,(1) if someone could help me with it by coding the image merging bit to
> combine all the different seeds so that an external program is not required.
> And (2), after starting the Progressive Render, it's impossible to stop it
> without actually killing the process, is there a way around this? I've had
> to use Campbell's method from the Cell Fracture addon just to refresh the UI
> and display progress..

For (1) you could run another blender instance in the background and
create a compositing node setup with python to merge images.

The other option is to simplify things and not do any merging at all
and just start again each time, just running render animation. This
would give you a 50% render time increase if you double the samples
each time (which to me seems somewhat more useful than adding a fixed
number of samples).

Regarding (2), I think you would need to change the code so that your
script is not the main loop but is listening to callbacks/events and
acts on those. You would invoke the render operator (invoke not
execute so it runs as a job that the user can cancel), and then wait
for the render to be finished or cancelled. There is a render_post
handler but launching a new render from that might be a problem as
it's still running the render then, so some trickery might be needed
with e.g. an operator listening to a timer that starts the next render
a bit later.

> Or perhaps there's a better way with more solid integration with the
> rendering process?
> Since it's on the Todo list, I assume it's eventually meant to be a part of
> blender itself and not simply an addon.

Integrating this natively will of course give a better UI and
integration. It needs changes in both Blender and Cycles, and is
closely related to implementing pause/resume rendering too, since
progressive animation render is like pausing a render for each frame
and then resuming it later.

I'd like to add this but it's a matter of time/priorities, I guess
users will be happy with an addon for now, unless a developer here has
time to work on a native implementation.

Brecht.