Daniel, M.2014-10-212014-10-2119961467-8659https://doi.org/10.1111/1467-8659.1540219Determining a tight bounding volume of all the surface normal vectors is of interest in surface modelling especially for intersection problems, in order to detect closed intersection curves. It is also important to determine quickly whether two such volumes intersect. This paper adresses both problems through the introduction of a pyramid with a convex planar base. For intersection problems, a different method has been proposed by M. Hohmeyer. The various solutions are discussed and compared.10.1111/1467-8659.1540219219-227