Function default_surface_material 

fn default_surface_material() -> StandardMaterial

Processes pending spawn requests from the scene tree panel. The material the editor attaches to a freshly-spawned primitive so it is immediately visible and editable. The engine projection has no implicit default material (a meshed entity without one is a clear, logged error), so the authoring tool supplies an explicit one — a neutral matte grey the user then tweaks in the inspector.