Geometry Nodes: Use a default value in the point scale node

This commit adds the ability to provide a default value to
`attribute_try_get_for_output` and uses it for the `Point Scale` node,
which is important because the node uses multiplication.

The idea is to keep "name-specific" functionality in nodes rather than in
the attribute API, otherwise the complexity will be hard to keep track of.
So this fix doesn't apply to the Attribute Vector Math node, but hopfully
that is okay since that's now a lower level node for this purpose anyway.

Differential Revision: https://developer.blender.org/D10115

1 files changed, 7 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/attribute_access.cc b/source/blender/blenkernel/intern/attribute_access.cc
index 6739294a2c4..a7939beae90 100644
--- a/source/blender/blenkernel/intern/attribute_access.cc
+++ b/source/blender/blenkernel/intern/attribute_access.cc
@@ -814,7 +814,8 @@ blender::bke::ReadAttributePtr GeometryComponent::attribute_get_constant_for_rea
 
 OutputAttributePtr GeometryComponent::attribute_try_get_for_output(const StringRef attribute_name,
                                                                    const AttributeDomain domain,
-                                                                   const CustomDataType data_type)
+                                                                   const CustomDataType data_type,
+                                                                   const void *default_value)
 {
   BLI_assert(this->attribute_domain_with_type_supported(domain, data_type));
 
@@ -827,6 +828,11 @@ OutputAttributePtr GeometryComponent::attribute_try_get_for_output(const StringR
   if (!attribute) {
     this->attribute_try_create(attribute_name, domain, data_type);
     attribute = this->attribute_try_get_for_write(attribute_name);
+    if (default_value != nullptr) {
+      void *data = attribute->get_span_for_write_only().data();
+      cpp_type->fill_initialized(default_value, data, attribute->size());
+      attribute->apply_span();
+    }
     return OutputAttributePtr(std::move(attribute));
   }