Geometry Nodes: Add default attribute name to field inputs/outputs

Geometry node group inputs and outputs get a new property that controls
the attribute name used for that field input/output when assigning the
node group to a modifier for the first time. If the default name is assigned
to an input, the default "Use attribute name" is true .

In order to properly detect when a node group is first assigned,
the modifier now clears its properties when clearing the node group.

Ref T96707

Differential Revision: https://developer.blender.org/D14761

release/scripts/startup/bl_ui/space_node.py

@@ -797,8 +797,10 @@ class NodeTreeInterfacePanel:
                     active_socket.bl_socket_idname.startswith(prefix)
                     for prefix in field_socket_prefixes
                 )
-                if in_out == 'OUT' and is_field_type:
-                    layout.prop(active_socket, "attribute_domain")
+                if is_field_type:
+                    if in_out == 'OUT':
+                        layout.prop(active_socket, "attribute_domain")
+                    layout.prop(active_socket, "default_attribute_name")
             active_socket.draw(context, layout)
 
 

source/blender/blenkernel/intern/node.cc

@@ -487,6 +487,9 @@ static void write_node_socket(BlendWriter *writer, bNodeSocket *sock)
     IDP_BlendWrite(writer, sock->prop);
   }
 
+  /* This property should only be used for group node "interface" sockets. */
+  BLI_assert(sock->default_attribute_name == nullptr);
+
   write_node_socket_default_value(writer, sock);
 }
 static void write_node_socket_interface(BlendWriter *writer, bNodeSocket *sock)
@@ -497,6 +500,8 @@ static void write_node_socket_interface(BlendWriter *writer, bNodeSocket *sock)
     IDP_BlendWrite(writer, sock->prop);
   }
 
+  BLO_write_string(writer, sock->default_attribute_name);
+
   write_node_socket_default_value(writer, sock);
 }
 
@@ -650,6 +655,7 @@ static void direct_link_node_socket(BlendDataReader *reader, bNodeSocket *sock)
   sock->typeinfo = nullptr;
   BLO_read_data_address(reader, &sock->storage);
   BLO_read_data_address(reader, &sock->default_value);
+  BLO_read_data_address(reader, &sock->default_attribute_name);
   sock->total_inputs = 0; /* Clear runtime data set before drawing. */
   sock->cache = nullptr;
   sock->declaration = nullptr;
@@ -2161,6 +2167,9 @@ static void node_socket_copy(bNodeSocket *sock_dst, const bNodeSocket *sock_src,
     }
   }
 
+  sock_dst->default_attribute_name = static_cast<char *>(
+      MEM_dupallocN(sock_src->default_attribute_name));
+
   sock_dst->stack_index = 0;
   /* XXX some compositor nodes (e.g. image, render layers) still store
    * some persistent buffer data here, need to clear this to avoid dangling pointers. */

source/blender/makesdna/DNA_node_types.h

@@ -139,6 +139,14 @@ typedef struct bNodeSocket {
   char label[64];
   char description[64];
 
+  /**
+   * The default attribute name to use for geometry nodes modifier output attribute sockets.
+   * \note Storing this pointer in every single socket exposes the bad design of using sockets
+   * to describe group inputs and outputs. In the future, it should be stored in socket
+   * declarations.
+   */
+  char *default_attribute_name;
+
   /** Cached data from execution. */
   void *cache;
 

source/blender/makesrna/intern/rna_nodetree.c

@@ -10890,6 +10890,14 @@ static void rna_def_node_socket_interface(BlenderRNA *brna)
       "Attribute domain used by the geometry nodes modifier to create an attribute output");
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_NodeSocketInterface_update");
 
+  prop = RNA_def_property(srna, "default_attribute_name", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_sdna(prop, NULL, "default_attribute_name");
+  RNA_def_property_ui_text(prop,
+                           "Default Attribute",
+                           "The attribute name used by default when the node group is used by a "
+                           "geometry nodes modifier");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_NodeSocketInterface_update");
+
   /* registration */
   prop = RNA_def_property(srna, "bl_socket_idname", PROP_STRING, PROP_NONE);
   RNA_def_property_string_sdna(prop, NULL, "typeinfo->idname");

source/blender/modifiers/intern/MOD_nodes.cc

@@ -628,6 +628,10 @@ static void init_socket_cpp_value_from_property(const IDProperty &property,
 void MOD_nodes_update_interface(Object *object, NodesModifierData *nmd)
 {
   if (nmd->node_group == nullptr) {
+    if (nmd->settings.properties) {
+      IDP_FreeProperty(nmd->settings.properties);
+      nmd->settings.properties = nullptr;
+    }
     return;
   }
 
@@ -680,7 +684,13 @@ void MOD_nodes_update_interface(Object *object, NodesModifierData *nmd)
       IDProperty *attribute_prop = IDP_New(IDP_STRING, &idprop, attribute_name_id.c_str());
       IDP_AddToGroup(nmd->settings.properties, attribute_prop);
 
-      if (old_properties != nullptr) {
+      if (old_properties == nullptr) {
+        if (socket->default_attribute_name && socket->default_attribute_name[0] != '\0') {
+          IDP_AssignString(attribute_prop, socket->default_attribute_name, MAX_NAME);
+          IDP_Int(use_attribute_prop) = 1;
+        }
+      }
+      else {
         IDProperty *old_prop_use_attribute = IDP_GetPropertyFromGroup(old_properties,
                                                                       use_attribute_id.c_str());
         if (old_prop_use_attribute != nullptr) {
@@ -709,7 +719,12 @@ void MOD_nodes_update_interface(Object *object, NodesModifierData *nmd)
     }
     IDP_AddToGroup(nmd->settings.properties, new_prop);
 
-    if (old_properties != nullptr) {
+    if (old_properties == nullptr) {
+      if (socket->default_attribute_name && socket->default_attribute_name[0] != '\0') {
+        IDP_AssignString(new_prop, socket->default_attribute_name, MAX_NAME);
+      }
+    }
+    else {
       IDProperty *old_prop = IDP_GetPropertyFromGroup(old_properties, idprop_name.c_str());
       if (old_prop != nullptr) {
         /* #IDP_CopyPropertyContent replaces the UI data as well, which we don't (we only
@@ -1728,8 +1743,13 @@ static void blendWrite(BlendWriter *writer, const ModifierData *md)
 static void blendRead(BlendDataReader *reader, ModifierData *md)
 {
   NodesModifierData *nmd = reinterpret_cast<NodesModifierData *>(md);
-  BLO_read_data_address(reader, &nmd->settings.properties);
-  IDP_BlendDataRead(reader, &nmd->settings.properties);
+  if (nmd->node_group == nullptr) {
+    nmd->settings.properties = nullptr;
+  }
+  else {
+    BLO_read_data_address(reader, &nmd->settings.properties);
+    IDP_BlendDataRead(reader, &nmd->settings.properties);
+  }
   nmd->runtime_eval_log = nullptr;
 }