setCustomSort( func ) {

		this.customSort = func;
		return this;

	}
Takes a sort a function that is run before render. The function takes a list of instances to
sort and a camera. The objects in the list include a "z" field to perform a depth-ordered sort with.

@param {Function} func - The custom sort function.
@return {BatchedMesh} A reference to this batched mesh.