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Geometry Nodes: new geometry attribute API

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Currently, there are two attribute API. The first, defined in `BKE_attribute.h` is
accessible from RNA and C code. The second is implemented with `GeometryComponent`
and is only accessible in C++ code. The second is widely used, but only being
accessible through the `GeometrySet` API makes it awkward to use, and even impossible
for types that don't correspond directly to a geometry component like `CurvesGeometry`.

This patch adds a new attribute API, designed to replace the `GeometryComponent`
attribute API now, and to eventually replace or be the basis of the other one.

The basic idea is that there is an `AttributeAccessor` class that allows code to
interact with a set of attributes owned by some geometry. The accessor itself has
no ownership. `AttributeAccessor` is a simple type that can be passed around by
value. That makes it easy to return it from functions and to store it in containers.

For const-correctness, there is also a `MutableAttributeAccessor` that allows
changing individual and can add or remove attributes.

Currently, `AttributeAccessor` is composed of two pointers. The first is a pointer
to the owner of the attribute data. The second is a pointer to a struct with
function pointers, that is similar to a virtual function table. The functions
know how to access attributes on the owner.

The actual attribute access for geometries is still implemented with the `AttributeProvider`
pattern, which makes it easy to support different sources of attributes on a
geometry and simplifies dealing with built-in attributes.

There are different ways to get an attribute accessor for a geometry:
* `GeometryComponent.attributes()`
* `CurvesGeometry.attributes()`
* `bke::mesh_attributes(const Mesh &)`
* `bke::pointcloud_attributes(const PointCloud &)`

All of these also have a `_for_write` variant that returns a `MutabelAttributeAccessor`.

Differential Revision: https://developer.blender.org/D15280
This commit is contained in:
Jacques Lucke
2022-07-08 16:16:56 +02:00
parent f391e8f316
commit b876ce2a4a
109 changed files with 2763 additions and 2808 deletions
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9
source/blender/editors/object/object_modifier.cc
View File

@@ -757,9 +757,7 @@ static bool modifier_apply_obdata(
BKE_mesh_nomain_to_mesh(mesh_applied, me, ob, &CD_MASK_MESH, true);
/* Anonymous attributes shouldn't be available on the applied geometry. */
MeshComponent component;
component.replace(me, GeometryOwnershipType::Editable);
component.attributes_remove_anonymous();
blender::bke::mesh_attributes_for_write(*me).remove_anonymous();
if (md_eval->type == eModifierType_Multires) {
multires_customdata_delete(me);
@@ -828,11 +826,12 @@ static bool modifier_apply_obdata(
BKE_report(reports, RPT_ERROR, "Evaluated geometry from modifier does not contain curves");
return false;
}
CurveComponent &component = geometry_set.get_component_for_write<CurveComponent>();
Curves &curves_eval = *geometry_set.get_curves_for_write();
/* Anonymous attributes shouldn't be available on the applied geometry. */
component.attributes_remove_anonymous();
blender::bke::CurvesGeometry::wrap(curves_eval.geometry)
.attributes_for_write()
.remove_anonymous();
/* If the modifier's output is a different curves data-block, copy the relevant information to
* the original. */