1 files changed, 9 insertions, 8 deletions

diff --git a/scene/3d/mesh_instance_3d.cpp b/scene/3d/mesh_instance_3d.cpp
index 10f3ab5c79..16de95bfb1 100644
--- a/scene/3d/mesh_instance_3d.cpp
+++ b/scene/3d/mesh_instance_3d.cpp
@@ -53,21 +53,22 @@ bool MeshInstance3D::_set(const StringName &p_name, const Variant &p_value) {
 	if (p_name.operator String().begins_with("surface_material_override/")) {
 		int idx = p_name.operator String().get_slicec('/', 1).to_int();
 
-		// This is a bit of a hack to ensure compatibility with older material
-		// overrides that start indexing at 0.
+		// This is a bit of a hack to ensure compatibility with material
+		// overrides that start indexing at 1.
 		// We assume that idx 0 is always read first, if its not, this won't work.
 		if (idx == 0) {
-			old_surface_index = true;
+			surface_index_0 = true;
 		}
-		if (old_surface_index) {
-			idx++;
+		if (!surface_index_0) {
+			// This means the file was created when the indexing started at 1, so decrease by one.
+			idx--;
 		}
 
 		if (idx > surface_override_materials.size() || idx < 0) {
 			return false;
 		}
 
-		set_surface_override_material(idx - 1, p_value);
+		set_surface_override_material(idx, p_value);
 		return true;
 	}
 
@@ -86,7 +87,7 @@ bool MeshInstance3D::_get(const StringName &p_name, Variant &r_ret) const {
 	}
 
 	if (p_name.operator String().begins_with("surface_material_override/")) {
-		int idx = p_name.operator String().get_slicec('/', 1).to_int() - 1;
+		int idx = p_name.operator String().get_slicec('/', 1).to_int();
 		if (idx >= surface_override_materials.size() || idx < 0) {
 			return false;
 		}
@@ -109,7 +110,7 @@ void MeshInstance3D::_get_property_list(List<PropertyInfo> *p_list) const {
 	}
 
 	if (mesh.is_valid()) {
-		for (int i = 1; i <= mesh->get_surface_count(); i++) {
+		for (int i = 0; i < mesh->get_surface_count(); i++) {
 			p_list->push_back(PropertyInfo(Variant::OBJECT, vformat("%s/%d", PNAME("surface_material_override"), i), PROPERTY_HINT_RESOURCE_TYPE, "BaseMaterial3D,ShaderMaterial", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_DEFERRED_SET_RESOURCE));
 		}
 	}