Avoid re-copying the scene when the scene is tagged for frame change.
For scenes with many objects scrubbing & jumping between first/last
caused noticeably worse performances.
Resolve by:
- Returning false from need_tag_cow_before_update when the recalc flag
is ID_RECALC_FRAME_CHANGE.
- Change deg_graph_tag_parameters_if_needed to consider
ID_RECALC_FRAME_CHANGE a clean flag.
Ref !104801
The depsgraph CoW mechanism is a bit of a misnomer. It creates an
evaluated copy for data-blocks regardless of whether the copy will
actually be written to. The point is to have physical separation between
original and evaluated data. This is in contrast to the commonly used
performance improvement of keeping a user count and copying data
implicitly when it needs to be changed. In Blender code we call this
"implicit sharing" instead. Importantly, the dependency graph has no
idea about the _actual_ CoW behavior in Blender.
Renaming this functionality in the despgraph removes some of the
confusion that comes up when talking about this, and will hopefully
make the depsgraph less confusing to understand initially too. Wording
like "the evaluated copy" (as opposed to the original data-block) has
also become common anyway.
Pull Request: https://projects.blender.org/blender/blender/pulls/118338
This node is needed to ensure evaluation order of scene and modifiers
which might access scene for custom data masks, or for the current
frame.
Move it to own component, so that evaluation of scene does not lead
to changes in the parameters component, hence does not trigger
driver evaluation.
Should be no functional changes.
Ref #117335
