Geometry Nodes: Support for dynamic attributes on curve splines

With this patch you will be able to add and remove attributes from curve
data inside of geometry nodes. The following is currently implemented:
* Adding attributes with any data type to splines or spline points.
* Support for working with multiple splines at the same time.
* Interaction with the three builtin point attributes.
* Resampling attributes in the resample node.

The following is not implemented in this patch:
* Joining attributes when joining splines with the join geometry node.
* Domain interpolation between spline and point domains.
* More efficient ways to call attribute operations once per spline.

Differential Revision: https://developer.blender.org/D11251

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/spline_bezier.cc b/source/blender/blenkernel/intern/spline_bezier.cc
index 58a8f46730a..0fd3efce033 100644
--- a/source/blender/blenkernel/intern/spline_bezier.cc
+++ b/source/blender/blenkernel/intern/spline_bezier.cc
@@ -55,6 +55,9 @@ void BezierSpline::set_resolution(const int value)
   this->mark_cache_invalid();
 }
 
+/**
+ * \warning Call #reallocate on the spline's attributes after adding all points.
+ */
 void BezierSpline::add_point(const float3 position,
                              const HandleType handle_type_start,
                              const float3 handle_position_start,
@@ -83,6 +86,7 @@ void BezierSpline::resize(const int size)
   radii_.resize(size);
   tilts_.resize(size);
   this->mark_cache_invalid();
+  attributes.reallocate(size);
 }
 
 MutableSpan<float3> BezierSpline::positions()