[Bf-committers] Proposition: Multilayer EXR support

[Gustav Göransson]

If both direction is allowed I think it could be wise to use the same
direction as other common applications like Nuke, After Effects, Photoshop
etc. which apparently uses the other direction. Or at least provide a "flip
direction" option in the OpenEXR output panel.

/gustav

On Fri, Jan 29, 2010 at 16:25, Fabian Fricke <frigi.f at googlemail.com> wrote:

> I'm just thinking out loud here but it's vaguely the same topic:
> I always wondered why the temp FSA samples are only being stored temporally
> and not in coherence with the rendered frames, thus allowing compositing
> after all frames were already renderd. Maybe as additional layers in the
> same file, or in a folder alongside the frames.
>
> I don't know if there has been any discussion about this when the feature
> was first introduced but I would think it's a desirable option.
>
> 2010/1/29 Ton Roosendaal <ton at blender.org>
>
> > Hi,
> >
> > It's not upside down, it's an accepted & documented option in exr that
> > has issues... both directions are allowed, but when i worked on it
> > there were weird things in the windows version of openexr or so... too
> > long ago to recall. Investige this?
> >
> > -Ton-
> >
> > ------------------------------------------------------------------------
> > Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
> > Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands
> >
> > On 29 Jan, 2010, at 15:34, Jeroen Bakker wrote:
> >
> > >  * Problem statement
> > > Multilayer EXR files are used in 2 places.
> > >
> > > 1. to temporarily store the render buffers to reduce the memory
> > > footprint between the render pass and the composition pass.
> > > 2. to store the final output image as a multilayer exr.
> > >
> > > the problem is that multilayer exr's are stored upside down. For 1
> > > it is
> > > not a problem as the file is temporarily and used by blender renderer.
> > > for 2: the output image makes the file's not easilly usable. You first
> > > have to flip the image, before you can use it.
> > >
> > > * Expectation
> > > the temporarily file must still be stored in the current form (upside
> > > down) for performance reasons.
> > > the output file must not be stored upside down, but still have all
> > > render layers available. (open file with exrdisplay -C
> > > RenderLayer.Combined.R filename.exr to see problem)
> > >
> > > Identifying the problem.
> > > both accesses the same function in openexr_api.cpp and both are
> > > triggered from the pipeline.c (blender renderer), but both have
> > > different requirements:
> > >
> > > * Proposition/alternatives
> > > there are several options how we can solve this:
> > > 1. leave all the same, but just before writing the multilayer exr
> > > output
> > > image, flip all render buffers. The implementation of the multilayer
> > > does not use the imbuf API, so will not effects other file formats and
> > > is easilly doable
> > > 2. update the imbuf api, to support multilayer images. more work, but
> > > more futureproof to possible other (professional, non existing) output
> > > formats
> > > 3. use the exr tiles to save the image upside down (is something in
> > > between solution 1 and 2)
> > >
> > > I would have chosen for option 1 as it is not that much work, and I
> > > don't know what the requirements are for other professional output
> > > formats. Solution 3
> > >
> > > Other issues in this area: the multilayer has is no default image/
> > > layer;
> > > all images are default black in other applications like nuke or
> > > exrdisplay.
> > >
> > > What do you think what is the wise thing to do?
> > > @Brecht, Campbell, is it OKE to patch pipeline as you are
> > > restructuring
> > > the renderer?
> > >
> > > Greetings,
> > > Jeroen Bakker.
> > >
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