AttachmentCounter

Incremented by the main thread before being attached to the scene, decremented by the rendering thread after removal. This counter exists to assert that operations are safe in order to help avoid race conditions. *** Runtime logic should NEVER rely on this value. ***

The only safe assertions to make are: AttachmentCounter == 0: The primitive is not exposed to the rendering

            thread, it is safe to modify shared members.
            This assertion is valid ONLY from the main thread.

AttachmentCounter >= 1: The primitive IS exposed to the rendering

            thread and therefore shared members must not
            be modified. This assertion may be made from
            any thread. Note that it is valid and expected
            for AttachmentCounter to be larger than 1, e.g.
            during reattachment.