1. A method of using a volatile or non-volatile computer-readable media or storage unit, the method comprising: storing a data structure for an original mesh surface that is provided with a bounding surface bounding the mesh surface and is provided with a tight inner surface, the data structure comprising: a first tessellation linking the tight inner surface to the original mesh surface; and a second tessellation linking the bounding surface to the tight inner surface, and using the data structure to at least one of: find an intersection with the original mesh surface; determine whether an intersection with the original mesh surface is occluded by the original mesh surface; and to identify an order of an intersection.