Geometry: Avoid unnecessary initialization when resizing data arrays

When resizing mesh and curves attribute storage, avoid initializing the
new memory for basic types. Also, avoid skipping "no free" layers; all
layers should be reallocated to the new size since they may be accessed.

The semantics introduced in 25237d2625078c6d1 are essential for this
change, because otherwise we don't have a way to construct non-trivial
types in the new memory.

In a basic test of the extrude node, I observed a performance
improvement of about 30%, from 55ms to 42ms.

Differential Revision: https://developer.blender.org/D15818

1 files changed, 22 insertions, 0 deletions

diff --git a/source/blender/geometry/intern/add_curves_on_mesh.cc b/source/blender/geometry/intern/add_curves_on_mesh.cc
index e06ee55afa0..bb5e2a0a28a 100644
--- a/source/blender/geometry/intern/add_curves_on_mesh.cc
+++ b/source/blender/geometry/intern/add_curves_on_mesh.cc
@@ -372,6 +372,28 @@ AddCurvesOnMeshOutputs add_curves_on_mesh(CurvesGeometry &curves,
 
   curves.fill_curve_types(new_curves_range, CURVE_TYPE_CATMULL_ROM);
 
+  /* Explicitly set all other attributes besides those processed above to default values. */
+  bke::MutableAttributeAccessor attributes = curves.attributes_for_write();
+  Set<std::string> attributes_to_skip{{"position",
+                                       "curve_type",
+                                       "surface_uv_coordinate",
+                                       ".selection_point_float",
+                                       ".selection_curve_float"}};
+  attributes.for_all(
+      [&](const bke::AttributeIDRef &id, const bke::AttributeMetaData /*meta_data*/) {
+        if (id.is_named() && attributes_to_skip.contains(id.name())) {
+          return true;
+        }
+        bke::GSpanAttributeWriter attribute = attributes.lookup_for_write_span(id);
+        const int new_elements_num = attribute.domain == ATTR_DOMAIN_POINT ? new_points_num :
+                                                                             new_curves_num;
+        const CPPType &type = attribute.span.type();
+        GMutableSpan new_data = attribute.span.take_back(new_elements_num);
+        type.fill_assign_n(type.default_value(), new_data.data(), new_data.size());
+        attribute.finish();
+        return true;
+      });
+
   return outputs;
 }