Automatic instancing

[trusktr]

Given some sub tree,

<lume-element3d>
	<lume-mesh has="phong-material sphere-geometry" ...></lume-mesh>

		<lume-element3d>
			<lume-mesh has="physical-material sphere-geometry" ...></lume-mesh>

			<lume-mesh has="phong-material sphere-geometry" ...></lume-mesh>
		</lume-element3d>

		<lume-element3d>
			<lume-mesh has="physical-material sphere-geometry" ...></lume-mesh>
		</lume-element3d>
</lume-element3d>

we'd be able to wrap it with auto instancing,

<lume-autoinstance>
	<lume-element3d>
		<!-- A -->
		<lume-mesh has="phong-material sphere-geometry" ...></lume-mesh>

		<lume-element3d>
			<!-- B -->
			<lume-mesh has="physical-material sphere-geometry" ...></lume-mesh>

			<!-- A -->
			<lume-mesh has="phong-material sphere-geometry" ...></lume-mesh>
		</lume-element3d>

		<lume-element3d>
			<!-- B -->
			<lume-mesh has="physical-material sphere-geometry" ...>
				<!-- A -->
				<lume-mesh has="phong-material sphere-geometry" ...></lume-mesh>
			</lume-mesh>
		</lume-element3d>
	</lume-element3d>
</lume-autoinstance>

and it would instance the meshes marked with A, ad the meshes marked with B, so the result would be like having two InstancedMeshes.

Maybe it can be behaviors:

	<lume-element3d has="autoinstance">
		<!-- ...same as before... -->
	</lume-element3d>