Fat surfaces: a trivariate approach to triangle-based interpolation on surfaces. - Robert E. Barnhill; Karsten Opitz; Helmut Pottmann (Comput. Aided Geom. Des., 1992)

Curvature analysis and visualization for functions defined on Euclidean spaces or surfaces. - Helmut Pottmann; Karsten Opitz (Comput. Aided Geom. Des., 1994)

Computing shortest paths on polyhedra: applications in geometric modeling and scientific visualization. - Karsten Opitz; Helmut Pottmann (Int. J. Comput. Geom. Appl., 1994)