source/blender/editors/include/ED_object.h

@@ -241,6 +241,9 @@ void ED_object_parent(struct Object *ob, struct Object *parent, int type, const
 char *ED_object_ot_drop_named_material_tooltip(struct bContext *C,
                                                const char *name,
                                                const int mval[2]);
+char *ED_object_ot_drop_geometry_nodes_tooltip(const struct bContext *C,
+                                               const struct PointerRNA *properties,
+                                               const int mval[2]);
 
 /* bitflags for enter/exit editmode */
 enum {

source/blender/editors/object/object_intern.h

@@ -62,6 +62,11 @@ void OBJECT_OT_clear_override_library(struct wmOperatorType *ot);
  * Assigns to object under cursor, only first material slot.
  */
 void OBJECT_OT_drop_named_material(struct wmOperatorType *ot);
+/**
+ * Used for drop-box.
+ * Assigns to object under cursor, creates a new geometry nodes modifier.
+ */
+void OBJECT_OT_drop_geometry_nodes(struct wmOperatorType *ot);
 /**
  * \note Only for empty-image objects, this operator is needed
  */

source/blender/editors/object/object_ops.c

@@ -262,6 +262,7 @@ void ED_operatortypes_object(void)
   WM_operatortype_append(OBJECT_OT_bake_image);
   WM_operatortype_append(OBJECT_OT_bake);
   WM_operatortype_append(OBJECT_OT_drop_named_material);
+  WM_operatortype_append(OBJECT_OT_drop_geometry_nodes);
   WM_operatortype_append(OBJECT_OT_unlink_data);
   WM_operatortype_append(OBJECT_OT_laplaciandeform_bind);
 

source/blender/editors/object/object_relations.c

@@ -99,6 +99,8 @@
 #include "ED_screen.h"
 #include "ED_view3d.h"
 
+#include "MOD_nodes.h"
+
 #include "object_intern.h"
 
 /* ------------------------------------------------------------------- */
@@ -2867,6 +2869,119 @@ void OBJECT_OT_drop_named_material(wmOperatorType *ot)
 
 /** \} */
 
+/* ------------------------------------------------------------------- */
+/** \name Drop Geometry Nodes on Object Operator
+ * \{ */
+
+char *ED_object_ot_drop_geometry_nodes_tooltip(const bContext *C,
+                                               const PointerRNA *properties,
+                                               const int mval[2])
+{
+  const Object *ob = ED_view3d_give_object_under_cursor(C, mval);
+  if (ob == NULL) {
+    return BLI_strdup("");
+  }
+
+  const uint32_t session_uuid = RNA_int_get(properties, "session_uuid");
+  const ID *id = BKE_libblock_find_session_uuid(CTX_data_main(C), ID_NT, session_uuid);
+  if (!id) {
+    return BLI_strdup("");
+  }
+
+  const char *tooltip = TIP_("Add modifier with node group \"%s\" on object \"%s\"");
+  return BLI_sprintfN(tooltip, id->name, ob->id.name);
+}
+
+static bool check_geometry_node_group_sockets(wmOperator *op, const bNodeTree *tree)
+{
+  const bNodeSocket *first_input = (const bNodeSocket *)tree->inputs.first;
+  if (!first_input) {
+    BKE_report(op->reports, RPT_ERROR, "The node group must have a geometry input socket");
+    return false;
+  }
+  if (first_input->type != SOCK_GEOMETRY) {
+    BKE_report(op->reports, RPT_ERROR, "The first input must be a geometry socket");
+    return false;
+  }
+  const bNodeSocket *first_output = (const bNodeSocket *)tree->outputs.first;
+  if (!first_output) {
+    BKE_report(op->reports, RPT_ERROR, "The node group must have a geometry output socket");
+    return false;
+  }
+  if (first_output->type != SOCK_GEOMETRY) {
+    BKE_report(op->reports, RPT_ERROR, "The first output must be a geometry socket");
+    return false;
+  }
+  return true;
+}
+
+static int drop_geometry_nodes_invoke(bContext *C, wmOperator *op, const wmEvent *event)
+{
+  Object *ob = ED_view3d_give_object_under_cursor(C, event->mval);
+  if (!ob) {
+    return OPERATOR_CANCELLED;
+  }
+
+  Main *bmain = CTX_data_main(C);
+  Scene *scene = CTX_data_scene(C);
+
+  const uint32_t uuid = RNA_int_get(op->ptr, "session_uuid");
+  bNodeTree *node_tree = (bNodeTree *)BKE_libblock_find_session_uuid(bmain, ID_NT, uuid);
+  if (!node_tree) {
+    return OPERATOR_CANCELLED;
+  }
+  if (node_tree->type != NTREE_GEOMETRY) {
+    BKE_report(op->reports, RPT_ERROR, "Node group must be a geometry node tree");
+    return OPERATOR_CANCELLED;
+  }
+
+  if (!check_geometry_node_group_sockets(op, node_tree)) {
+    return OPERATOR_CANCELLED;
+  }
+
+  NodesModifierData *nmd = (NodesModifierData *)ED_object_modifier_add(
+      op->reports, bmain, scene, ob, node_tree->id.name + 2, eModifierType_Nodes);
+  if (!nmd) {
+    BKE_report(op->reports, RPT_ERROR, "Could not add geometry nodes modifier");
+    return OPERATOR_CANCELLED;
+  }
+
+  nmd->node_group = node_tree;
+  id_us_plus(&node_tree->id);
+  MOD_nodes_update_interface(ob, nmd);
+
+  DEG_id_tag_update(&ob->id, ID_RECALC_GEOMETRY);
+  WM_event_add_notifier(C, NC_OBJECT | ND_MODIFIER, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+/** \} */
+
+void OBJECT_OT_drop_geometry_nodes(wmOperatorType *ot)
+{
+  ot->name = "Drop Geometry Node Group on Object";
+  ot->idname = "OBJECT_OT_drop_geometry_nodes";
+
+  ot->invoke = drop_geometry_nodes_invoke;
+  ot->poll = ED_operator_view3d_active;
+
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO | OPTYPE_INTERNAL;
+
+  PropertyRNA *prop = RNA_def_int(ot->srna,
+                                  "session_uuid",
+                                  0,
+                                  INT32_MIN,
+                                  INT32_MAX,
+                                  "Session UUID",
+                                  "Session UUID of the geometry node group being dropped",
+                                  INT32_MIN,
+                                  INT32_MAX);
+  RNA_def_property_flag(prop, (PropertyFlag)(PROP_HIDDEN | PROP_SKIP_SAVE));
+}
+
+/** \} */
+
 /* ------------------------------------------------------------------- */
 /** \name Unlink Object Operator
  * \{ */

source/blender/editors/space_view3d/space_view3d.cc

@@ -37,6 +37,7 @@
 #include "BKE_idprop.h"
 #include "BKE_lattice.h"
 #include "BKE_layer.h"
+#include "BKE_lib_id.h"
 #include "BKE_lib_remap.h"
 #include "BKE_main.h"
 #include "BKE_mball.h"
@@ -702,6 +703,52 @@ static bool view3d_volume_drop_poll(bContext * /*C*/, wmDrag *drag, const wmEven
   return (drag->type == WM_DRAG_PATH) && (drag->icon == ICON_FILE_VOLUME);
 }
 
+static bool view3d_geometry_nodes_drop_poll(bContext *C, wmDrag *drag, const wmEvent *event)
+{
+  if (!view3d_drop_id_in_main_region_poll(C, drag, event, ID_NT)) {
+    return false;
+  }
+
+  if (drag->type == WM_DRAG_ID) {
+    const bNodeTree *node_tree = reinterpret_cast<const bNodeTree *>(
+        WM_drag_get_local_ID(drag, ID_NT));
+    if (!node_tree) {
+      return false;
+    }
+    return node_tree->type == NTREE_GEOMETRY;
+  }
+
+  if (drag->type == WM_DRAG_ASSET) {
+    const wmDragAsset *asset_data = WM_drag_get_asset_data(drag, ID_NT);
+    if (!asset_data) {
+      return false;
+    }
+    const IDProperty *tree_type = BKE_asset_metadata_idprop_find(asset_data->metadata, "type");
+    if (!tree_type || IDP_Int(tree_type) != NTREE_GEOMETRY) {
+      return false;
+    }
+    if (wmDropBox *drop_box = drag->drop_state.active_dropbox) {
+      const uint32_t uuid = RNA_int_get(drop_box->ptr, "session_uuid");
+      const bNodeTree *node_tree = reinterpret_cast<const bNodeTree *>(
+          BKE_libblock_find_session_uuid(CTX_data_main(C), ID_NT, uuid));
+      if (node_tree) {
+        return node_tree->type == NTREE_GEOMETRY;
+      }
+    }
+  }
+  return true;
+}
+
+static char *view3d_geometry_nodes_drop_tooltip(bContext *C,
+                                                wmDrag * /*drag*/,
+                                                const int xy[2],
+                                                struct wmDropBox *drop)
+{
+  ARegion *region = CTX_wm_region(C);
+  int mval[2] = {xy[0] - region->winrct.xmin, xy[1] - region->winrct.ymin};
+  return ED_object_ot_drop_geometry_nodes_tooltip(C, drop->ptr, mval);
+}
+
 static void view3d_ob_drop_matrix_from_snap(V3DSnapCursorState *snap_state,
                                             Object *ob,
                                             float obmat_final[4][4])
@@ -930,6 +977,12 @@ static void view3d_dropboxes()
                  view3d_id_drop_copy,
                  WM_drag_free_imported_drag_ID,
                  view3d_mat_drop_tooltip);
+  WM_dropbox_add(lb,
+                 "OBJECT_OT_drop_geometry_nodes",
+                 view3d_geometry_nodes_drop_poll,
+                 view3d_id_drop_copy,
+                 WM_drag_free_imported_drag_ID,
+                 view3d_geometry_nodes_drop_tooltip);
   WM_dropbox_add(lb,
                  "VIEW3D_OT_background_image_add",
                  view3d_ima_bg_drop_poll,