It's better to calculate the size of a spline before creating it, and this
should simplify refactoring to a data structure that stores all point
attribute contiguously (see T94193). The mesh to curve conversion is
simplified slightly now, it creates the curve output after gathering all
of the result vertex indices. This should be more efficient too, since
it only grows an index vector for each spline, not a whole spline.
This patch refactors the instance-realization code and adds new functionality.
* Named and anonymous attributes are propagated from instances to the
realized geometry. If the same attribute exists on the geometry and on an
instance, the attribute on the geometry has precedence.
* The id attribute has special handling to avoid creating the same id on many
output points. This is necessary to make e.g. the Random Value node work
as expected afterwards.
Realizing instance attributes has an effect on existing files, especially due to the
id attribute. To avoid breaking existing files, the Realize Instances node now has
a legacy option that is enabled for all already existing Realize Instances nodes.
Removing this legacy behavior does affect some existing files (although not many).
We can decide whether it's worth to remove the old behavior as a separate step.
This refactor also improves performance when realizing instances. That is mainly
due to multi-threading. See D13446 to get the file used for benchmarking. The
curve code is not as optimized as it could be yet. That's mainly because the storage
for these attributes might change soonish and it wasn't worth optimizing for the
current storage format right now.
```
1,000,000 x mesh vertex: 530 ms -> 130 ms
1,000,000 x simple cube: 1290 ms -> 190 ms
1,000,000 x point: 1000 ms -> 150 ms
1,000,000 x curve spiral: 1740 ms -> 330 ms
1,000,000 x curve line: 1110 ms -> 210 ms
10,000 x subdivided cylinder: 170 ms -> 40 ms
10 x subdivided spiral: 180 ms -> 180 ms
```
Differential Revision: https://developer.blender.org/D13446
Goals of this refactor:
* Simplify creating virtual arrays.
* Simplify passing virtual arrays around.
* Simplify converting between typed and generic virtual arrays.
* Reduce memory allocations.
As a quick reminder, a virtual arrays is a data structure that behaves like an
array (i.e. it can be accessed using an index). However, it may not actually
be stored as array internally. The two most important implementations
of virtual arrays are those that correspond to an actual plain array and those
that have the same value for every index. However, many more
implementations exist for various reasons (interfacing with legacy attributes,
unified iterator over all points in multiple splines, ...).
With this refactor the core types (`VArray`, `GVArray`, `VMutableArray` and
`GVMutableArray`) can be used like "normal values". They typically live
on the stack. Before, they were usually inside a `std::unique_ptr`. This makes
passing them around much easier. Creation of new virtual arrays is also
much simpler now due to some constructors. Memory allocations are
reduced by making use of small object optimization inside the core types.
Previously, `VArray` was a class with virtual methods that had to be overridden
to change the behavior of a the virtual array. Now,`VArray` has a fixed size
and has no virtual methods. Instead it contains a `VArrayImpl` that is
similar to the old `VArray`. `VArrayImpl` should rarely ever be used directly,
unless a new virtual array implementation is added.
To support the small object optimization for many `VArrayImpl` classes,
a new `blender::Any` type is added. It is similar to `std::any` with two
additional features. It has an adjustable inline buffer size and alignment.
The inline buffer size of `std::any` can't be relied on and is usually too
small for our use case here. Furthermore, `blender::Any` can store
additional user-defined type information without increasing the
stack size.
Differential Revision: https://developer.blender.org/D12986
This commit adds a fields version of the mesh to curve node, with a
field for the input selection. In order to reduce code duplication,
it adds the mesh to curve conversion to the new geometry module
and calls that implementation from both places.
More details on the geometry module can be found here: T86869
Differential Revision: https://developer.blender.org/D12579
