Previously it could have happened on every request to evaluated scene
or view layer.
This commit also removes expansion of view layer and scene from iterator.
Iterator is not to be used before depsgraph is evaluated.
The depsgraph was always created within a fixed evaluation context. Passing
both risks the depsgraph and evaluation context not matching, and it
complicates the Python API where we'd have to expose both which is not so
easy to understand.
This also removes the global evaluation context in main, which assumed there
to be a single active scene and view layer.
Differential Revision: https://developer.blender.org/D3152
Cycles old behaviour is to hide the duplicator on rendering at all times.
We have since a few months an option in 2.8 to control the duplicator
visibility on its own. However when the duplicator is also duplicated, things
were not working properly.
What we do now is, in addition to the duplicator visibility control, is to not
have the source collection of the duplicator object to ever influence its
visibility when the object is been duplicated.
So if the user wants to reproduce Cycles old behaviour all that is required is
to have different collections, one for the original to-be duplicated objects
that you hide in for the view layer used in the final render. And another
collection with only the first duplicator (which in turn duplicates other
duplicators).
I know this all may sound confusing, so please just give it a try, it's simpler
than it sounds.
The issue was caused by Cycles allocating ID property in a temporary object
which gets overwritten and thrown away every so often.
Now dependency graph will try to reliably check whether ID properties from
a temp object are to be freed.
This allows a duplicator (as known as dupli parent) to be in a visible
collection so its duplicated objects are visible, however while being
invisible for the final render.
An object that is a particle emitter is also considered a duplicator.
Many thanks for the reviewers for the extense feedback.
Reviewers: sergey, campbellbarton
Differential Revision: https://developer.blender.org/D2966
Since we are ditching layers from Blender (2.8) we need a replacement to
control groups visibility. This commit introduces collections as the building
blocks for groups, allowing users to control visibility as well as overrides
for groups.
Features
========
* Groups now have collections
This way you can change the visibility of a collection inside a group, and add
overrides which are part of the group and are prioritized over other overrides.
* Outliner
Groups can inspect their collections, change visibility, and add/remove members.
To change an override of a group collection, you need to select an instance of
the group, and then you can choose "group" in the collection properties editor
to edit this group active collection instead of the view layer one.
* Dupli groups overrides
We can now have multiple instances of the same group with an original "override"
and different overrides depending on the collection the instanced object is part
of.
Technical
=========
* Layers
We use the same api for groups and scene as much as possible.
Reviewers: sergey (depsgraph), mont29 (read/write and user count)
Differential Revision: https://developer.blender.org/D2892
