Improve the 3D editor manipulation gizmo

- Allow some tolerance when clicking the plane move/scale,
  even if the click is actually slightly outside the plane
  (similar to Blender).
- Make the rotate manipulation circles visually thinner to be
  less distracting.
- Make the hovered color less saturated to be more distinguishable
  from the non-hovered state.
  - Don't set brightness above 1.0 to prevent the gizmo from glowing
    when hovered.

editor/plugins/node_3d_editor_plugin.cpp

@@ -874,14 +874,18 @@ bool Node3DEditorViewport::_gizmo_select(const Vector2 &p_screenpos, bool p_high
 				Vector3 ivec2 = gt.basis.get_axis((i + 1) % 3).normalized();
 				Vector3 ivec3 = gt.basis.get_axis((i + 2) % 3).normalized();
 
-				Vector3 grabber_pos = gt.origin + (ivec2 + ivec3) * gs * (GIZMO_PLANE_SIZE + GIZMO_PLANE_DST);
+				// Allow some tolerance to make the plane easier to click,
+				// even if the click is actually slightly outside the plane.
+				const Vector3 grabber_pos = gt.origin + (ivec2 + ivec3) * gs * (GIZMO_PLANE_SIZE + GIZMO_PLANE_DST * 0.6667);
 
 				Vector3 r;
 				Plane plane(gt.origin, gt.basis.get_axis(i).normalized());
 
 				if (plane.intersects_ray(ray_pos, ray, &r)) {
 					float dist = r.distance_to(grabber_pos);
-					if (dist < (gs * GIZMO_PLANE_SIZE)) {
+					// Allow some tolerance to make the plane easier to click,
+					// even if the click is actually slightly outside the plane.
+					if (dist < (gs * GIZMO_PLANE_SIZE * 1.5)) {
 						float d = ray_pos.distance_to(r);
 						if (d < col_d) {
 							col_d = d;
@@ -974,14 +978,18 @@ bool Node3DEditorViewport::_gizmo_select(const Vector2 &p_screenpos, bool p_high
 				Vector3 ivec2 = gt.basis.get_axis((i + 1) % 3).normalized();
 				Vector3 ivec3 = gt.basis.get_axis((i + 2) % 3).normalized();
 
-				Vector3 grabber_pos = gt.origin + (ivec2 + ivec3) * gs * (GIZMO_PLANE_SIZE + GIZMO_PLANE_DST);
+				// Allow some tolerance to make the plane easier to click,
+				// even if the click is actually slightly outside the plane.
+				Vector3 grabber_pos = gt.origin + (ivec2 + ivec3) * gs * (GIZMO_PLANE_SIZE + GIZMO_PLANE_DST * 0.6667);
 
 				Vector3 r;
 				Plane plane(gt.origin, gt.basis.get_axis(i).normalized());
 
 				if (plane.intersects_ray(ray_pos, ray, &r)) {
 					float dist = r.distance_to(grabber_pos);
-					if (dist < (gs * GIZMO_PLANE_SIZE)) {
+					// Allow some tolerance to make the plane easier to click,
+					// even if the click is actually slightly outside the plane.
+					if (dist < (gs * GIZMO_PLANE_SIZE * 1.5)) {
 						float d = ray_pos.distance_to(r);
 						if (d < col_d) {
 							col_d = d;
@@ -2744,9 +2752,7 @@ void Node3DEditorViewport::_draw() {
 				handle_color = get_theme_color("accent_color", "Editor");
 				break;
 		}
-		handle_color.a = 1.0;
-		const float brightness = 1.3;
-		handle_color *= Color(brightness, brightness, brightness);
+		handle_color = handle_color.from_hsv(handle_color.get_h(), 0.25, 1.0, 1);
 
 		RenderingServer::get_singleton()->canvas_item_add_line(
 				ci,
@@ -5477,8 +5483,7 @@ void Node3DEditor::_init_indicators() {
 			gizmo_color[i] = mat;
 
 			Ref<StandardMaterial3D> mat_hl = mat->duplicate();
-			const float brightness = 1.3;
-			const Color albedo = Color(col.r * brightness, col.g * brightness, col.b * brightness);
+			const Color albedo = col.from_hsv(col.get_h(), 0.25, 1.0, 1);
 			mat_hl->set_albedo(albedo);
 			gizmo_color_hl[i] = mat_hl;
 
@@ -5585,7 +5590,7 @@ void Node3DEditor::_init_indicators() {
 				surftool->begin(Mesh::PRIMITIVE_TRIANGLES);
 
 				int n = 128; // number of circle segments
-				int m = 6; // number of thickness segments
+				int m = 3; // number of thickness segments
 
 				real_t step = Math_TAU / n;
 				for (int j = 0; j < n; ++j) {
@@ -5789,7 +5794,7 @@ void Node3DEditor::_init_indicators() {
 				surftool->commit(scale_plane_gizmo[i]);
 
 				Ref<StandardMaterial3D> plane_mat_hl = plane_mat->duplicate();
-				plane_mat_hl->set_albedo(Color(col.r * 1.3, col.g * 1.3, col.b * 1.3));
+				plane_mat_hl->set_albedo(col.from_hsv(col.get_h(), 0.25, 1.0, 1));
 				plane_gizmo_color_hl[i] = plane_mat_hl; // needed, so we can draw planes from both sides
 			}
 		}