This commit is a work forward having less updates during playback, which speeds
things up a lot here. The idea is simple: stop update all copy-on-write
datablocks (which implies full re-evaluation actually) on frame change and
re-use existing evaluated meshes as much as possible.
This brings playback speed to 24 fps on the dino test scene here. Performance
drops down a lot when armature is animated tho, but that's because of need of
tangent space calculation which we can't do much about from just a dependency
graph.
Hopefully this doesn't make copy-on-write too unstable, quick tests here are
surviving fine.
BKE_scene_copy explicitly ignores visibility of "source" collections make all
collections visible. This is also tested by regression tests.
While it seems more logical to simply preserve all possible visibility flags
and overrides, don't feel like submitting to a behavior-changes without talking
to author of those guards first.
This commit fixes cycles material preview.
If object is only listed in collection but not added to any of layers we shouldn't create
placeholder for it, because otherwise we'll leave lots of placeholder ID nodes.
Question: can we make this exception to be more reliable?
Note that some little parts of code have been dissabled because eval_ctx
was not available there. This should be resolved once DerivedMesh is
replaced.
The remapping code was creating plkaceholders for objects coming from legacy
bases, but since those objects were never created by dependency graph (since
they are supposed to be ignored) the copy on write relations creation was
confused.
Now we do some special trickery to clear legacy bases on copy on write.
Those checks are not always helpful, since id remapping doesn't want to
worry about which components to tag for update. Perhaps in the future we
will introduce special flag which would mean "tag everything possible"/
This is the fake ID nature of compositor again. Need to discard such
pointers before freeing datablock even for scenes (before it was done
for objects only).
Previously it was possible to run into situation when armature is constructed prior to
objects which are used for it's constraints. This was causing wrong scene evaluation.
Now we create placeholders for objects used by armature in case they don't have ID node
yet, which ensures we have proper mapping from original to copy-on-write ID pointer.
This shows the bug when IK solver doesn't update reliably when targeted an external
object and when that object is handled by build_object() after the armature.
