[Bf-committers] Multiview branch feedback

[Brecht Van Lommel]

Hi,

Thanks for the feedback. Dalai might have a different opinion but here
is my take on this design.

On Wed, Jun 12, 2013 at 4:22 AM, Adriano Oliveira
<adriano.ufrb at gmail.com> wrote:
> In my humble opinion, the problems are related to the fact that the very
> implementations that allow stereo preview in 3d viewport are leading to
> lack of control in Image Editor and Composite. To be more specific:

The current workflow is to composite the left view and right view
using the same node setup. Being able to run compositing for stereo
renders without needing special nodes is very valuable I think. It
makes it easy to switch stereo on, and switch it back off as well
without having to fiddle with nodes. Of course there may be more
advanced scenarios where you want special nodes to somehow use both
left and right views in a single node setup, but I don't see why you
would make that a requirement.

Can you be more specific about why you think it has to work this way,
like specific node operations that you need to be able to do that are
not possible now?

> *What I am not sure of and proposals:*
>
> -          The same approach that allows previewing stereoscopy in 3d
> viewport is not as useful in Image Editor (render outcome) and Composite. I
> think it is better that Image Editor only shows stereo images as long as
> they have been composed in Composite as such.

Why is this better? Isn't it useful to be able to enable stereo, press
render, and get a stereo image immediately?

> -          For that reason, I would remove the “3-D” option in “Select
> View”. Better: In Image Editor I would remove this new “Select View”, for
> it leads to confusion when dealing with Composite outputs. Even though it
> may seams repetitive, it is more correct and informative to add the views
> ids in the old “Select Pass”, by adding suffixes: Composite.Left;
> Composite.Right; Z.Left; Z.Right… These suffixes should be added whenever
> the user activates L or R views in Render Views.

I'm not sure why this is more correct, I don't see why representing
these as passes instead of views helps? The only reason OpenEXR stores
them this way is to keep the file format compatible, but for user
interfaces it makes sense to represent things more organized and not
at this low level. We could have done the same for RenderLayers and
RenderPasses, putting them all together in one big list. They full
names in OpenEXR files are RenderLayer.Z.Left, etc. But this does not
make for a better UI in my opinion.

> -          In consequence, stereo automated previews shoud not be a UI or
> Blender Window general option in Preferences, but an option only related to
> a single 3d Viewport, in the very Viewport.

I can see how it would be useful to have control over this at the
viewport level. But even if we have that a default stereo viewing
method in the user preferences seems like a good idea to me? It
depends on the monitor and operating system configuration so it
belongs in user preferences I think.

> -          In Composite, Render Layers nodes are lacking a switch for
> choosing Left or Right, like Image nodes already have. Both should offer
> Left and Right switches, and…

I think there were some plans to allow you to use a specific view in
the Render Layer instead of automatically left/right but I'm not sure
what the status of that is. You would get the options Auto / Left /
Right and then you can choose which view to use. If it's there for
images I guess it will be there soon for Render Layer nodes too.

> -          Render Layers and Image nodes should NOT offer a “3-D”
> switchfor it is not useful in Composite and leads to confusion. 3-D is
> not a
> channel within Render Layer or Image, it’s just a fast composition option
> of two layers, based on generic parameters.

Not sure why this is a problem. These settings in the header are just
a way to specify what you want to view. So why not specify there that
you want to view Left, Right or 3D? Is it because it might confusing
users into thinking this data will be saved in files? I can see that,
maybe the UI should be designed to make that more clear. The option to
view 3D should be there somewhere though.

> -          It is more logical to get stereo outcome composing Left and
> Right in a new “Stereo Node”, that would offer: 02 inputs (channels from
> toggled L / R Render Layers or Image nodes), 01 selector with presented
> stereo modes (side by side, over under…); 01 input numerical parameter for
> convergence correction; 01 composed stereo image output.

I don't agree with this, I think that's a file format and display
feature. Right now we only support saving stereo OpenEXR images, and
views do not need to be composited together for that. If we support
for example PNS or JPS in the future we can composite together the
images appropriate for those file formats and write all the proper
metadata along with it. Even now we could have an option to save
images anaglyph or side by side in regular file formats.

If this stereo compositing happens in the compositing nodes then the
result is no longer file format and stereo viewing method agnostic and
it becomes complicated for the user to ensure that the compositing
setup matches the file format. If you want to view the render result
on the different monitor you might need to change the compositing
nodes setup. Even worse, you wouldn't be able to view the result on
your monitor in one way but save it in another.


Overall, I think the way it's designed to work in Blender makes a lot
of sense. The whole pipeline really understands stereo, from the 3D
viewport to rendering and compositing. That's different than some
other applications where you have to deal with plugins and manually
split and merge render passes, composite stereo images, etc, and I
think we can make things more user friendly because it's natively
supported.

Think about how nice it is if you can just take existing files, enable
stereo, press render and see the result in 3D. And then being able to
easily turn it off when you want to work on shading and lighting, or
switch file formats quickly, etc.

Brecht.