Fix is a bit ugly, but cannot think of another solution for now, at
least this **should** not break anything else.
And now I go find myself a very remote, high and lonely mountain, climb
to its top, roar "I hate proxies!" a few times, and relax hearing the echos...
This also renames some flags/variables to be more generic for updating
purposes. The call used here was previously only used for updating
paint data, but as it was reused here, flags and variables were renamed
to accomodate more clearly to the new usages.
This is annoying especially for exporters who do use mesh name, since it
broke any relation with actual Mesh naming in original Blend file.
Unfortunately, we cannot avoid the extra .xxx digits. ;)
This makes the node menus aware of the Cycles/Eevee distinction, and
only show the relevant nodes for the current engine. Names have also
been changed to accomodate for the new output node system.
This makes Eevee consistent with Cycles, by having a single output node,
and multiple shader nodes that connect to it.
Note that node systems for Eevee saved before this will be missing the
output node, and thus will show an invalid material. This is easily
resolved by connecting the shader output to a new output node.
< Dependency graph Copy-on-Write >
--------------------------------
\ ^__^
\ (oo)\_______
(__)\ )\/\
||----w |
|| ||
This is an initial commit of Copy-on-write support added to dependency graph.
Main priority for now: get playback (Alt-A) and all operators (selection,
transform etc) to work with the new concept of clear separation between
evaluated data coming from dependency graph and original data coming from
.blend file (and stored in bmain).
= How does this work? =
The idea is to support Copy-on-Write on the ID level. This means, we duplicate
the whole ID before we cann it's evaluaiton function. This is currently done
in the following way:
- At the depsgraph construction time we create "shallow" copy of the ID
datablock, just so we know it's pointer in memory and can use for function
bindings.
- At the evaluaiton time, the copy of ID get's "expanded" (needs a better
name internally, so it does not conflict with expanding datablocks during
library linking), which means the content of the datablock is being
copied over and all IDs are getting remapped to the copied ones.
Currently we do the whole copy, in the future we will support some tricks
here to prevent duplicating geometry arrays (verts, edges, loops, faces
and polys) when we don't need that.
- Evaluation functions are operating on copied datablocks and never touching
original datablock.
- There are some cases when we need to know non-ID pointers for function
bindings. This mainly applies to scene collections and armatures. The
idea of dealing with this is to "expand" copy-on-write datablock at
the dependency graph build time. This might introduce some slowdown to the
dependency graph construction time, but allows us to have minimal changes
in the code and avoid any hash look-up from evaluation function (one of
the ideas to avoid using pointers as function bindings is to pass name
of layer or a bone to the evaluation function and look up actual data based
on that name).
Currently there is a special function in depsgraph which does such a
synchronization, in the future we might want to make it more generic.
At some point we need to synchronize copy-on-write version of datablock with
the original version. This happens, i.e., when we change active object or
change selection. We don't want any actual evaluation of update flush happening
for such thins, so now we have a special update tag:
DEG_id_tag_update((id, DEG_TAG_COPY_ON_WRITE)
- For the render engines we now have special call for the dependency graph to
give evaluated datablock for the given original one. This isn't fully ideal
but allows to have Cycles viewport render.
This is definitely a subject for further investigation / improvement.
This call will tag copy-on-write component tagged for update without causing
updates to be flushed to any other objects, causing chain reaction of updates.
This tag is handy when selection in the scene changes.
This basically summarizes ideas underneath this commit. The code should be
reasonably documented.
Here is a demo of dependency graph with all copy-on-write stuff in it:
https://developer.blender.org/F635468
= What to expect to (not) work? =
- Only meshes are properly-ish aware of copy-on-write currently, Non-mesh
geometry will probably crash or will not work at all.
- Armatures will need similar depsgraph built-time expansion of the copied
datablock.
- There are some extra tags / relations added, to keep things demo-able but
which are slowing things down for evaluation.
- Edit mode works for until click selection is used (due to the selection
code using EditDerivedMesh created ad-hoc).
- Lots of tools will lack tagging synchronization of copied datablock for
sync with original ID.
= How to move forward? =
There is some tedious work related on going over all the tools, checking
whether they need to work with original or final evaluated object and make
the required changes.
Additionally, there need synchronization tag done in fair amount of tools
and operators as well. For example, currently it's not possible to change
render engine without re-opening the file or forcing dependency graph for
re-build via python console.
There is also now some thoughts required about copying evaluated properties
between objects or from collection to a new object. Perhaps easiest way
would be to move base flag flush to Object ID node and tag new objects for
update instead of doing manual copy.
here is some WIP patch which moves such evaluaiton / flush:
https://developer.blender.org/F635479
Lots of TODOs in the code, with possible optimization.
= How to test? =
This is a feature under heavy development, so obviously it is disabled by
default. The only reason it goes to 2.8 branch is to avoid possible merge
hell.
In order to enable this feature use WITH_DEPSGRAPH_COPY_ON_WRITE CMake
configuration option.
Children where always getting at least one segment of fixed length...
Now fully hidden ones (zero length) get no segment at all.
Note that even very short ones keep getting one 'unit' length segment - would
rather avoid changing that at this point, given how complex children
particles 'length' can get with all kind of modifiers... Think we can
live with that for now anyway.
'Convert To...' Object operation has very weird effect of actually
working at obdata level, not object level, which means *all* objects
(even unselected/hidden/in other scenes/...) using same obdata will be
converted to new selected type.
IMHO this is very bad behavior, but... not a bug really, so do not
change this for now.
But at least, do not do that when working on some linked data, else it
leaves Blend file in invalid (incoherent) state until next reload.
So workaround for now is to enforce the 'Keep Original' option when some
linked object/obdata is affected by the operation.
Also fixed somewhat broken usercount handling in Curve->Mesh part.
Eeeeeek!^2 Calling unconditionnaly ID freeing `BKE_libblock_free()` on a
datablock (ob->data, i.e. Curve) that may be used elsewhere...
Veryveryvery bad!
Noisy change, but safe, and better do it sooner than later if we are to
rework copying code. Also, previous commit shows this *is* useful to
catch some mistakes.
This is similar to some other datablocks. Mainly applies to collections,
so freeing scene does not involve changing any non-directly owned data.
There are two main usecases foreseen for the future:
- Less CPU ticks on bmain free, where everything is freed anyway and
there is no need to preserve id counters.
- Easier freeing of temporary data, including data which is used by
depsgraph's copy-on-write mechanism.
Neither of those are currently implemented, but will be shortly.
There is no reason to be special for workspace and go against other design
decision in Blender. If something like this is going to become a common
practice in Blender it should be well thought and well tested, including
tests of all supported compilers and configurations.
This feature was relying on type re-definition, which is not only confusing
but also available in C11 only.
