The copies don't update themselves, their names aren't files to read again: after a change of the weather or the season the material got its new textures and its copies kept the old ones. They are made again from it then, under their handles. primitive() of an empty handle or one past the banks read out of the bank list; it gives no_primitive there, -1 from the renderer.
Erase() empties a chunk and keeps its handle to be filled again, for geometry made anew as it changes. Primitive() tells whether a chunk holds triangles or strips, -1 from a renderer which doesn't know. The VAO bank reused the buffer of a chunk of the same length even when the userdata came or went, the layout of the buffer differing then.
