When active dependency graph is evaluated, it will apply animation,
drivers and scalar evaluation data (such as object matrix) to an
original datablock. This way operators and tools can easily read
data from original datablock.
This will simplify porting them to copy-on-write, and solve issues
when some operator will allocate new datablock based on original one,
and will want to read data from it.
After discussion with Sergey and Dalai, we have decided to remove
this option completely. We're getting to the point where it is almost
impossible to really use 2.8 without COW, and keeping the old option
running ends up diverting dev resources away towards tracking down
and fixing problems with a parallel system that will be going away.
As was decided at today's dev kickoff, we're now moving to having
Copy-on-Write enabled by default, as 2.8 is barely functional with
it off.
To run Blender *without* COW (e.g. for testing), use:
--disable-copy-on-write
OVERVIEW
* In 2.7 terminology, all layers and groups are now collection datablocks.
* These collections are nestable, linkable, instanceable, overrideable, ..
which opens up new ways to set up scenes and link + override data.
* Viewport/render visibility and selectability are now a part of the collection
and shared across all view layers and linkable.
* View layers define which subset of the scene collection hierarchy is excluded
for each. For many workflows one view layer can be used, these are more of an
advanced feature now.
OUTLINER
* The outliner now has a "View Layer" display mode instead of "Collections",
which can display the collections and/or objects in the view layer.
* In this display mode, collections can be excluded with the right click menu.
These will then be greyed out and their objects will be excluded.
* To view collections not linked to any scene, the "Blender File" display mode
can be used, with the new filtering option to just see Colleciton datablocks.
* The outliner right click menus for collections and objects were reorganized.
* Drag and drop still needs to be improved. Like before, dragging the icon or
text gives different results, we'll unify this later.
LINKING AND OVERRIDES
* Collections can now be linked into the scene without creating an instance,
with the link/append operator or from the collections view in the outliner.
* Collections can get static overrides with the right click menu in the outliner,
but this is rather unreliable and not clearly communicated at the moment.
* We still need to improve the make override operator to turn collection instances
into collections with overrides directly in the scene.
PERFORMANCE
* We tried to make performance not worse than before and improve it in some
cases. The main thing that's still a bit slower is multiple scenes, we have to
change the layer syncing to only updated affected scenes.
* Collections keep a list of their parent collections for faster incremental
updates in syncing and caching.
* View layer bases are now in a object -> base hash to avoid quadratic time
lookups internally and in API functions like visible_get().
VERSIONING
* Compatibility with 2.7 files should be improved due to the new visibility
controls. Of course users may not want to set up their scenes differently
now to avoid having separate layers and groups.
* Compatibility with 2.8 is mostly there, and was tested on Eevee demo and Hero
files. There's a few things which are know to be not quite compatible, like
nested layer collections inside groups.
* The versioning code for 2.8 files is quite complicated, and isolated behind
#ifdef so it can be removed at the end of the release cycle.
KNOWN ISSUES
* The G-key group operators in the 3D viewport were left mostly as is, they
need to be modified still to fit better.
* Same for the groups panel in the object properties. This needs to be updated
still, or perhaps replaced by something better.
* Collections must all have a unique name. Less restrictive namespacing is to
be done later, we'll have to see how important this is as all objects within
the collections must also have a unique name anyway.
* Full scene copy and delete scene are exactly doing the right thing yet.
Differential Revision: https://developer.blender.org/D3383https://code.blender.org/2018/05/collections-and-groups/
Scene, view layer and mode are now set in the constructor and never changed.
Time is updated on frame changes to indicate which frame is being or has been
evaluated last.
This is a step towards making EvaluationContext obsolete.
Differential Revision: https://developer.blender.org/D3144
Introduced explicit ID property node for driers in depsgraph,
so it is clear what is the input for driver, and what is the
output.
This also solved relations builder throwing lots of errors
due to ID property not being found.
This allows us to:
- Not mock around with tags stored in a global space,
and not to iterate over all datablocks in the database
to clear the tags.
- Properly deal with datablocks which might not be in main database.
While it sounds crazy, it might be handy when dealing with preview,
or some partial scene updates, such as motion paths.
- Avoids majority of places where depsgraph construction needed bmain.
This is something what could help in blender2.8 branch.
From tests with production file here did not see any measurable slowdown.
Hopefully, there is no functional changes :)
It is not possible to address transform at particular position of constraint
stack, and when constraint is being addressed is usually from driver variable.
This fixes some of dependency cycles reported in T54083.
This is kind of doesn't matter where macro itself is defined.
We should stick to the following:
- If some macro is actually more an inline function, follow regular
function name conventions.
- If macro is a macro, type it in capitals. Use module prefix if that
helps readability or it if helps avoiding accidents.
One thing i'm not fully happy with is all this is_same_* functions. Need to
get rid of this by probably adding explicit entry/init/whatever nodes and
maybe making node criteria aware of whether key will be used as "from" or
as "to" node.
The idea is to allow iterating over ID nodes in exact order of their
construction, and in order which will not change dependent on memory
pointers or anything.
Currently this is a no-visible-changes change, but the idea is to use this
dedicated flag to tell which exact components of ID changed, make it more
granular than just OBJECT and OBJECT_DATA. Allow setting this field based
on what components new dependency graph flushed on evaluation.
We can't use a single component here, sine it might consist of multiple
operations. So, for example, having driver operation will confuse targets
of another driver.
