Simplify the GPUParticles3D editor gizmo to improve readability

- Remove handles as users should use the Generate Visibility AABB
  option whenever possible, so manual resizing isn't needed often.
  (For particles that move quickly and have Local Coords disabled,
  Extra Cull Margin can be increased in the GeometryInstance3D
  properties in the inspector.)
- Remove translucent filled part of the gizmo to be more consistent
  with GeometryInstance3D's recently introduced Custom AABB gizmo.
- Remove center marker as it can visually obstruct particles.

This paves the way for future emission shape gizmos which will
feature handles.

editor/plugins/gizmos/gpu_particles_3d_gizmo_plugin.cpp

@@ -41,9 +41,7 @@ GPUParticles3DGizmoPlugin::GPUParticles3DGizmoPlugin() {
 	Color gizmo_color = EDITOR_DEF_RST("editors/3d_gizmos/gizmo_colors/particles", Color(0.8, 0.7, 0.4));
 	create_material("particles_material", gizmo_color);
 	gizmo_color.a = MAX((gizmo_color.a - 0.2) * 0.02, 0.0);
-	create_material("particles_solid_material", gizmo_color);
 	create_icon_material("particles_icon", EditorNode::get_singleton()->get_editor_theme()->get_icon(SNAME("GizmoGPUParticles3D"), EditorStringName(EditorIcons)));
-	create_handle_material("handles");
 }
 
 bool GPUParticles3DGizmoPlugin::has_gizmo(Node3D *p_spatial) {
@@ -62,96 +60,6 @@ bool GPUParticles3DGizmoPlugin::is_selectable_when_hidden() const {
 	return true;
 }
 
-String GPUParticles3DGizmoPlugin::get_handle_name(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary) const {
-	switch (p_id) {
-		case 0:
-			return "Size X";
-		case 1:
-			return "Size Y";
-		case 2:
-			return "Size Z";
-		case 3:
-			return "Pos X";
-		case 4:
-			return "Pos Y";
-		case 5:
-			return "Pos Z";
-	}
-
-	return "";
-}
-
-Variant GPUParticles3DGizmoPlugin::get_handle_value(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary) const {
-	GPUParticles3D *particles = Object::cast_to<GPUParticles3D>(p_gizmo->get_node_3d());
-	return particles->get_visibility_aabb();
-}
-
-void GPUParticles3DGizmoPlugin::set_handle(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary, Camera3D *p_camera, const Point2 &p_point) {
-	GPUParticles3D *particles = Object::cast_to<GPUParticles3D>(p_gizmo->get_node_3d());
-
-	Transform3D gt = particles->get_global_transform();
-	Transform3D gi = gt.affine_inverse();
-
-	bool move = p_id >= 3;
-	p_id = p_id % 3;
-
-	AABB aabb = particles->get_visibility_aabb();
-	Vector3 ray_from = p_camera->project_ray_origin(p_point);
-	Vector3 ray_dir = p_camera->project_ray_normal(p_point);
-
-	Vector3 sg[2] = { gi.xform(ray_from), gi.xform(ray_from + ray_dir * 4096) };
-
-	Vector3 ofs = aabb.get_center();
-
-	Vector3 axis;
-	axis[p_id] = 1.0;
-
-	if (move) {
-		Vector3 ra, rb;
-		Geometry3D::get_closest_points_between_segments(ofs - axis * 4096, ofs + axis * 4096, sg[0], sg[1], ra, rb);
-
-		float d = ra[p_id];
-		if (Node3DEditor::get_singleton()->is_snap_enabled()) {
-			d = Math::snapped(d, Node3DEditor::get_singleton()->get_translate_snap());
-		}
-
-		aabb.position[p_id] = d - 1.0 - aabb.size[p_id] * 0.5;
-		particles->set_visibility_aabb(aabb);
-
-	} else {
-		Vector3 ra, rb;
-		Geometry3D::get_closest_points_between_segments(ofs, ofs + axis * 4096, sg[0], sg[1], ra, rb);
-
-		float d = ra[p_id] - ofs[p_id];
-		if (Node3DEditor::get_singleton()->is_snap_enabled()) {
-			d = Math::snapped(d, Node3DEditor::get_singleton()->get_translate_snap());
-		}
-
-		if (d < 0.001) {
-			d = 0.001;
-		}
-		//resize
-		aabb.position[p_id] = (aabb.position[p_id] + aabb.size[p_id] * 0.5) - d;
-		aabb.size[p_id] = d * 2;
-		particles->set_visibility_aabb(aabb);
-	}
-}
-
-void GPUParticles3DGizmoPlugin::commit_handle(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary, const Variant &p_restore, bool p_cancel) {
-	GPUParticles3D *particles = Object::cast_to<GPUParticles3D>(p_gizmo->get_node_3d());
-
-	if (p_cancel) {
-		particles->set_visibility_aabb(p_restore);
-		return;
-	}
-
-	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
-	ur->create_action(TTR("Change Particles AABB"));
-	ur->add_do_method(particles, "set_visibility_aabb", particles->get_visibility_aabb());
-	ur->add_undo_method(particles, "set_visibility_aabb", p_restore);
-	ur->commit_action();
-}
-
 void GPUParticles3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 	p_gizmo->clear();
 
@@ -168,33 +76,9 @@ void GPUParticles3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {
 			lines.push_back(b);
 		}
 
-		Vector<Vector3> handles;
-
-		for (int i = 0; i < 3; i++) {
-			Vector3 ax;
-			ax[i] = aabb.position[i] + aabb.size[i];
-			ax[(i + 1) % 3] = aabb.position[(i + 1) % 3] + aabb.size[(i + 1) % 3] * 0.5;
-			ax[(i + 2) % 3] = aabb.position[(i + 2) % 3] + aabb.size[(i + 2) % 3] * 0.5;
-			handles.push_back(ax);
-		}
-
-		Vector3 center = aabb.get_center();
-		for (int i = 0; i < 3; i++) {
-			Vector3 ax;
-			ax[i] = 1.0;
-			handles.push_back(center + ax);
-			lines.push_back(center);
-			lines.push_back(center + ax);
-		}
-
 		Ref<Material> material = get_material("particles_material", p_gizmo);
 
 		p_gizmo->add_lines(lines, material);
-
-		Ref<Material> solid_material = get_material("particles_solid_material", p_gizmo);
-		p_gizmo->add_solid_box(solid_material, aabb.get_size(), aabb.get_center());
-
-		p_gizmo->add_handles(handles, get_material("handles"));
 	}
 
 	Ref<Material> icon = get_material("particles_icon", p_gizmo);

editor/plugins/gizmos/gpu_particles_3d_gizmo_plugin.h

@@ -43,11 +43,6 @@ public:
 	bool is_selectable_when_hidden() const override;
 	void redraw(EditorNode3DGizmo *p_gizmo) override;
 
-	String get_handle_name(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary) const override;
-	Variant get_handle_value(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary) const override;
-	void set_handle(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary, Camera3D *p_camera, const Point2 &p_point) override;
-	void commit_handle(const EditorNode3DGizmo *p_gizmo, int p_id, bool p_secondary, const Variant &p_restore, bool p_cancel = false) override;
-
 	GPUParticles3DGizmoPlugin();
 };