Node that instances a [MultiMesh]. [MultiMeshInstance] is a specialized node to instance [GeometryInstance]s based on a [MultiMesh] resource. This is useful to optimize the rendering of a high amount of instances of a given mesh (for example trees in a forest or grass strands). $DOCS_URL/tutorials/3d/vertex_animation/animating_thousands_of_fish.html $DOCS_URL/tutorials/3d/using_multi_mesh_instance.html $DOCS_URL/tutorials/optimization/using_multimesh.html The [MultiMesh] resource that will be used and shared among all instances of the [MultiMeshInstance].