Use collision detection ray to reposition an object already in the scene

editor/plugins/node_3d_editor_plugin.cpp

@@ -672,6 +672,7 @@ void Node3DEditorViewport::cancel_transform() {
 		sp->set_global_transform(se->original);
 	}
 
+	collision_reposition = false;
 	finish_transform();
 	set_message(TTR("Transform Aborted."), 3);
 }
@@ -1801,7 +1802,7 @@ void Node3DEditorViewport::_sinput(const Ref<InputEvent> &p_event) {
 				if (b->is_pressed()) {
 					clicked_wants_append = b->is_shift_pressed();
 
-					if (_edit.mode != TRANSFORM_NONE && _edit.instant) {
+					if (_edit.mode != TRANSFORM_NONE && (_edit.instant || collision_reposition)) {
 						commit_transform();
 						break; // just commit the edit, stop processing the event so we don't deselect the object
 					}
@@ -2400,30 +2401,43 @@ void Node3DEditorViewport::_sinput(const Ref<InputEvent> &p_event) {
 			cancel_transform();
 		}
 		if (!is_freelook_active() && !k->is_echo()) {
-			if (ED_IS_SHORTCUT("spatial_editor/instant_translate", p_event) && _edit.mode != TRANSFORM_TRANSLATE) {
+			if (ED_IS_SHORTCUT("spatial_editor/instant_translate", p_event) && (_edit.mode != TRANSFORM_TRANSLATE || collision_reposition)) {
 				if (_edit.mode == TRANSFORM_NONE) {
 					begin_transform(TRANSFORM_TRANSLATE, true);
-				} else if (_edit.instant) {
+				} else if (_edit.instant || collision_reposition) {
 					commit_transform();
 					begin_transform(TRANSFORM_TRANSLATE, true);
 				}
 			}
 			if (ED_IS_SHORTCUT("spatial_editor/instant_rotate", p_event) && _edit.mode != TRANSFORM_ROTATE) {
 				if (_edit.mode == TRANSFORM_NONE) {
 					begin_transform(TRANSFORM_ROTATE, true);
-				} else if (_edit.instant) {
+				} else if (_edit.instant || collision_reposition) {
 					commit_transform();
 					begin_transform(TRANSFORM_ROTATE, true);
 				}
 			}
 			if (ED_IS_SHORTCUT("spatial_editor/instant_scale", p_event) && _edit.mode != TRANSFORM_SCALE) {
 				if (_edit.mode == TRANSFORM_NONE) {
 					begin_transform(TRANSFORM_SCALE, true);
-				} else if (_edit.instant) {
+				} else if (_edit.instant || collision_reposition) {
 					commit_transform();
 					begin_transform(TRANSFORM_SCALE, true);
 				}
 			}
+			if (ED_IS_SHORTCUT("spatial_editor/collision_reposition", p_event) && editor_selection->get_selected_node_list().size() == 1 && !collision_reposition) {
+				if (_edit.mode == TRANSFORM_NONE || _edit.instant) {
+					if (_edit.mode == TRANSFORM_NONE) {
+						_compute_edit(_edit.mouse_pos);
+					} else {
+						commit_transform();
+						_compute_edit(_edit.mouse_pos);
+					}
+					_edit.mode = TRANSFORM_TRANSLATE;
+					collision_reposition = true;
+				}
+			}
+
 		}
 
 		// Freelook doesn't work in orthogonal mode.
@@ -3074,6 +3088,19 @@ void Node3DEditorViewport::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_PHYSICS_PROCESS: {
+			if (collision_reposition) {
+				List<Node *> &selection = editor_selection->get_selected_node_list();
+
+				if (selection.size() == 1) {
+					Node3D *first_selected_node = Object::cast_to<Node3D>(selection.front()->get());
+					double snap = EDITOR_GET("interface/inspector/default_float_step");
+					int snap_step_decimals = Math::range_step_decimals(snap);
+					set_message(TTR("Translating:") + " (" + String::num(first_selected_node->get_global_position().x, snap_step_decimals) + ", " +
+							String::num(first_selected_node->get_global_position().y, snap_step_decimals) + ", " + String::num(first_selected_node->get_global_position().z, snap_step_decimals) + ")");
+					first_selected_node->set_global_position(spatial_editor->snap_point(_get_instance_position(_edit.mouse_pos)));
+				}
+			}
+
 			if (!update_preview_node) {
 				return;
 			}
@@ -3968,7 +3995,7 @@ void Node3DEditorViewport::update_transform_gizmo_view() {
 		return;
 	}
 
-	bool show_gizmo = spatial_editor->is_gizmo_visible() && !_edit.instant && transform_gizmo_visible;
+	bool show_gizmo = spatial_editor->is_gizmo_visible() && !_edit.instant && transform_gizmo_visible && !collision_reposition;
 	for (int i = 0; i < 3; i++) {
 		Transform3D axis_angle;
 		if (xform.basis.get_column(i).normalized().dot(xform.basis.get_column((i + 1) % 3).normalized()) < 1.0) {
@@ -4243,6 +4270,18 @@ void Node3DEditorViewport::assign_pending_data_pointers(Node3D *p_preview_node,
 	accept = p_accept;
 }
 
+void _insert_rid_recursive(Node *node, HashSet<RID> &rids) {
+	CollisionObject3D *co = Object::cast_to<CollisionObject3D>(node);
+	if (co) {
+		rids.insert(co->get_rid());
+	}
+
+	for (int i = 0; i < node->get_child_count(); i++) {
+		Node *child = node->get_child(i);
+		_insert_rid_recursive(child, rids);
+	}
+}
+
 Vector3 Node3DEditorViewport::_get_instance_position(const Point2 &p_pos) const {
 	const float MAX_DISTANCE = 50.0;
 	const float FALLBACK_DISTANCE = 5.0;
@@ -4252,7 +4291,22 @@ Vector3 Node3DEditorViewport::_get_instance_position(const Point2 &p_pos) const
 
 	PhysicsDirectSpaceState3D *ss = get_tree()->get_root()->get_world_3d()->get_direct_space_state();
 
+	HashSet<RID> rids;
+
+	if (!preview_node->is_inside_tree()) {
+		List<Node *> &selection = editor_selection->get_selected_node_list();
+
+		Node3D *first_selected_node = Object::cast_to<Node3D>(selection.front()->get());
+
+		Array children = first_selected_node->get_children();
+
+		if (first_selected_node) {
+			_insert_rid_recursive(first_selected_node, rids);
+		}
+	}
+
 	PhysicsDirectSpaceState3D::RayParameters ray_params;
+	ray_params.exclude = rids;
 	ray_params.from = world_pos;
 	ray_params.to = world_pos + world_ray * camera->get_far();
 
@@ -4880,6 +4934,7 @@ void Node3DEditorViewport::commit_transform() {
 	}
 	undo_redo->commit_action();
 
+	collision_reposition = false;
 	finish_transform();
 	set_message("");
 }
@@ -5477,6 +5532,7 @@ Node3DEditorViewport::Node3DEditorViewport(Node3DEditor *p_spatial_editor, int p
 	ED_SHORTCUT("spatial_editor/instant_translate", TTR("Begin Translate Transformation"));
 	ED_SHORTCUT("spatial_editor/instant_rotate", TTR("Begin Rotate Transformation"));
 	ED_SHORTCUT("spatial_editor/instant_scale", TTR("Begin Scale Transformation"));
+	ED_SHORTCUT("spatial_editor/collision_reposition", TTR("Reposition Using Collisions"));
 
 	preview_camera = memnew(CheckBox);
 	preview_camera->set_text(TTR("Preview"));

editor/plugins/node_3d_editor_plugin.h

@@ -245,6 +245,7 @@ class Node3DEditorViewport : public Control {
 	bool auto_orthogonal;
 	bool lock_rotation;
 	bool transform_gizmo_visible = true;
+	bool collision_reposition = false;
 	real_t gizmo_scale;
 
 	bool freelook_active;
@@ -338,7 +339,6 @@ class Node3DEditorViewport : public Control {
 		TRANSFORM_ROTATE,
 		TRANSFORM_TRANSLATE,
 		TRANSFORM_SCALE
-
 	};
 	enum TransformPlane {
 		TRANSFORM_VIEW,