Added material_overlay property to MeshInstance3D

Applying overlay materials into multi-surface meshes currently
requires adding a next pass material to all the surfaces, which
might be cumbersome when the material is to be applied to a range
of different geometries. This also makes it not trivial to use
AnimationPlayer to control the material in case of visual effects.
The material_override property is not an option as it works
replacing the active material for the surfaces, not adding a new pass.

This commit adds the material_overlay property to GeometryInstance3D
(and therefore MeshInstance3D), having the same reach as
material_override (that is, all surfaces) but adding a new material
pass on top of the active materials, instead of replacing them.

1 files changed, 1 insertions, 0 deletions

diff --git a/servers/rendering/renderer_scene.h b/servers/rendering/renderer_scene.h
index ecafb7bc08..20ca49cd71 100644
--- a/servers/rendering/renderer_scene.h
+++ b/servers/rendering/renderer_scene.h
@@ -95,6 +95,7 @@ public:
 	virtual void instance_geometry_set_flag(RID p_instance, RS::InstanceFlags p_flags, bool p_enabled) = 0;
 	virtual void instance_geometry_set_cast_shadows_setting(RID p_instance, RS::ShadowCastingSetting p_shadow_casting_setting) = 0;
 	virtual void instance_geometry_set_material_override(RID p_instance, RID p_material) = 0;
+	virtual void instance_geometry_set_material_overlay(RID p_instance, RID p_material) = 0;
 
 	virtual void instance_geometry_set_visibility_range(RID p_instance, float p_min, float p_max, float p_min_margin, float p_max_margin, RS::VisibilityRangeFadeMode p_fade_mode) = 0;
 	virtual void instance_geometry_set_lightmap(RID p_instance, RID p_lightmap, const Rect2 &p_lightmap_uv_scale, int p_slice_index) = 0;