4.3 Spatial schema (ISO 19107)
145
A B-spline surface (class GM_BSplineSurface) is a rational or polynomial parametric surface that is represented by control points, basis functions and possibly
weights. If the weights are aB equal then the spline is piecewise polynomial. If they
are not equal then the spline is piecewise rational.
GM_PolyhedralSurface
A polyhedral surface (class GM_PolyhedraISurface) is a surface composed of
polygon surfaces (class GM_Polygon) connected along their common boundary
curves. This differs from the generic surface (class GM_Surface) only in the restrietion on the types of surface patches acceptable.
Fig. 4.21. GM_PolyhedralSurface
GM_ TriangulatedSurface
A triangulated surface (class GM _ TriangulatedSurface) is a polyhedral surface
that is composed only of triangles (class GM _Triangle ). There is no restrietion on
how the triangulation is derived.
Fig. 4.22. GM_Tin