Geometry Nodes: Add named attribute nodes behind experimental flag

This commit adds three nodes:
- `Remove Attribute`: Removes an attribute with the given name
- `Named Attribute`: A field input node
- `Store Named Attribute`: Puts results of a field in a named attribute

They are added behind a new experimental feature flag, because further
development of attribute search and name dependency visualization will
happen as separate steps.

Ref T91742

Differential Revision: https://developer.blender.org/D12685

1 files changed, 87 insertions, 0 deletions

diff --git a/source/blender/nodes/geometry/nodes/node_geo_remove_attribute.cc b/source/blender/nodes/geometry/nodes/node_geo_remove_attribute.cc
new file mode 100644
index 00000000000..202241affeb
--- /dev/null
+++ b/source/blender/nodes/geometry/nodes/node_geo_remove_attribute.cc
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "node_geometry_util.hh"
+
+#include "NOD_socket_search_link.hh"
+
+namespace blender::nodes::node_geo_remove_attribute_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Geometry>(N_("Geometry"));
+  b.add_input<decl::String>(N_("Name")).is_attribute_name();
+  b.add_output<decl::Geometry>(N_("Geometry"));
+}
+
+static void node_gather_link_searches(GatherLinkSearchOpParams &params)
+{
+  if (U.experimental.use_named_attribute_nodes == 0) {
+    return;
+  }
+  const NodeDeclaration &declaration = *params.node_type().fixed_declaration;
+  search_link_ops_for_declarations(params, declaration.inputs());
+  search_link_ops_for_declarations(params, declaration.outputs());
+}
+
+static void node_geo_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry_set = params.extract_input<GeometrySet>("Geometry");
+  const std::string name = params.extract_input<std::string>("Name");
+  if (name.empty() || !U.experimental.use_named_attribute_nodes) {
+    params.set_output("Geometry", std::move(geometry_set));
+    return;
+  }
+
+  std::atomic<bool> attribute_exists = false;
+  std::atomic<bool> cannot_delete = false;
+
+  geometry_set.modify_geometry_sets([&](GeometrySet &geometry_set) {
+    for (const GeometryComponentType type : {GEO_COMPONENT_TYPE_MESH,
+                                             GEO_COMPONENT_TYPE_POINT_CLOUD,
+                                             GEO_COMPONENT_TYPE_CURVE,
+                                             GEO_COMPONENT_TYPE_INSTANCES}) {
+      if (geometry_set.has(type)) {
+        /* First check if the attribute exists before getting write access,
+         * to avoid potentially expensive unnecessary copies. */
+        const GeometryComponent &read_only_component = *geometry_set.get_component_for_read(type);
+        if (read_only_component.attribute_exists(name)) {
+          attribute_exists = true;
+        }
+        else {
+          continue;
+        }
+
+        GeometryComponent &component = geometry_set.get_component_for_write(type);
+        if (!component.attribute_try_delete(name)) {
+          cannot_delete = true;
+        }
+      }
+    }
+  });
+
+  if (!attribute_exists) {
+    params.error_message_add(NodeWarningType::Info,
+                             TIP_("Attribute does not exist: \"") + name + "\"");
+  }
+  if (cannot_delete) {
+    params.error_message_add(NodeWarningType::Info,
+                             TIP_("Cannot delete attribute with name \"") + name + "\"");
+  }
+
+  params.set_output("Geometry", std::move(geometry_set));
+}
+
+}  // namespace blender::nodes::node_geo_remove_attribute_cc
+
+void register_node_type_geo_remove_attribute()
+{
+  namespace file_ns = blender::nodes::node_geo_remove_attribute_cc;
+
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_REMOVE_ATTRIBUTE, "Remove Attribute", NODE_CLASS_ATTRIBUTE);
+  ntype.declare = file_ns::node_declare;
+  ntype.geometry_node_execute = file_ns::node_geo_exec;
+  ntype.gather_link_search_ops = file_ns::node_gather_link_searches;
+  nodeRegisterType(&ntype);
+}