FPNTrianglesimplements curved PN (Point-Normal) Triangles (Curved PN Triangles, Vlachos, 2001). Each PN triangle replaces one original flat triangle by a curved shape that is retriangulated into a number of small subtriangles. The geometry of a PN triangle is defined as one cubic Bezier patch using control points. The patch matches the point and normal information at the vertices of the original flat triangle.