Old behavior: tagging ID with DEG_TAG_COPY_ON_WRITE will do copy-on-write
(as requested), but will also flush changes to all operations with depends
on it. This means, for example, tagging object for copy-on-write will force
its modifier stack to be evaluated.
This was needed in the earlier days of copy-on-write when things were not
well defined and when lots of areas were not doing proper tagging.
New behavior: tagging ID with DEG_TAG_COPY_ON_WRITE will only ensure copy
of the dadatblock is up to date, without flushing updates to any dependencies.
This means following things:
- We can update parts of ID without invoking heavy computation of other
parts of same ID. For example, tagging object for COPY_ON_WRITE update
on mode change will not force modifiers stack to update.
- If some dependent datablock is dependent on pointers which are invalidated
by copy-on-write (like, evaluated mesh referencing custom data layers from
original mesh), this will either require explicit tag or explicit relation
in the dependency graph.
Currently can not find a faulty case since tagging of mesh happens with
either 0 (which means, everything) or with GEOMETRY, which also forces
all dependent modifier stacks to be re-evaluated.
This fixes missing PBVH when going into sculpt mode (sculpt mode toggle
was tagging object for COPY_ON_WRITE update, which was forcing modifier
stack to be updated, which was freeing PBVH.
Some other operations might also become faster with this change.
Shading is supposed to be dealing with draw manager batch cached
thingamajigs, but was causing full object update.
This was causing both flickering in sculpt mode (PBVH was removed,
why it was SOMETIMES restored before draw is a mystery), and was
also causing things to be really slow.
This way we guarantee that animation component on the datablock will
totally wait for action to be fully evaluated before attempting to
evaluate f-curves.
Fixes T55642: Inconsistent result on animated DoF file
To find all effectors in the scene, we need to loop over all objects.
Doing this during depsgraph evaluation caused crashes because not all
objects are guaranteed to be evaluated yet.
To fix this, we now cache the relations as part of the dependency graph
build. As a bonus this also makes evaluation faster for big scenes,
since looping over all objects for each particle system is slow.
Fixes T55156.
Transform evaluation does depend on that matrix, but relation was never
in dependency graph. It was not even in the old dependency graph, which
makes me wonder how this thing worked reliably to begin with.
Should fix flickering issue in the render farm.
Transform evaluation doesn't not depend on objects which are being duplicated,
so should not be any regressions here.
The whole relation should probably be gone as it's kind of rooting back to
legacy times, but that would need more clear research and investigation and
regression testing.
Note this is now separate from H key hiding, and meant for more persistent
ways to define which objects are relevant to the viewport or render.
This avoids some cases where you'd have to create collection specifically
to hide objects for viewport/render.
Currently done for mesh batch cache update, and for base flags sync.
Those components do not need anything from original object, and hence
can skip CoW tag and have faster update after them used.
Completely ignore animation for legacy zero update tag.
If one needs animation to be evaluated, tag with proper update tag, stop relying
on direct assignment of adt->>recalc with zero update tag for DEG.
This commit might cause missing updates when needed, those needs to be looked
into once they happen.
This makes evaluated objects to point to a non-evaluated collection,
which is already really bad. What is even more worse, objects in those
collections are not evaluated either.
Proper solution would be to implement visibility flag for nodes, which
will be set to 0 for transform/geometry components, but which will be
1 for copy-on-write components.
This way we will guarantee consistency of dependency graph.
For now this change is good enough and unlocks production.
Fixes T55375: Crash when changing visibility of instanced collection
Fixes T55357: Particle geometry crash
