STEP AP203 (ISO 10303-203) B-Spline Information

What I want: * Information about STEP AP203 (ISO 10303-203) Schema * Specifically, what are the parameters required for b_spline_curve_with_knots and a b_spline_surface_with_knots * The schema are available at [login to view URL] * How do the knots, control points and weights work? * Examples: If I have a conic curve (ellipse, parabola, hyperbola), how do I specify the corresponding b_spline_curve_with_knots? How do I specify a surface that is a conic of revolution (ellipsoid, paraboloid, hyperboloid) in STEP AP203? If I have a conic surface that is bounded by an off-axis cylinder, how do I specify the boundary curves? If I have a conic surface that is bounded by a rectangle, how do I specify the boundary curves? Deliverables 1. A written description of how to create (or a well commented C function for creating) a conic of revolution as a b_spline_surface_with_knots (or something more appropriate) in STEP AP203 based on the vertex curvature and eccentricity or conic constant. The formula for my conics is: z=(c*y^2)/(1+sqrt(1-(1+k) c^2 y^2) where c is the vertex curvature and k is the conic constant (k=-e^2), where e is the eccentricity (0=sphere, 1=parabola). Assume that only c, k and the maximum value of y are known. If the parameters are specified in millimeters, the surface must be accurate to 0.1 micron. 2. A written description of how to create (or a well commented C function for creating) a STEP AP203 b_spline_surface_with_knots from a plane curve rotated about an axis. The plane curve is given as a series of points. If the parameters are specified in millimeters, the surface must be accurate to 0.1 micron. 3. A written description of how to create (or a well commented C function for creating) STEP AP203 bounding curves (face_outer_bound + edge_loop + oriented_edge + edge_curve) for both of the above surfaces. The edge is generated by a cylinder with an axis parallel to (but not coincident with) the axis of rotation of the surface. You may assume the ability to generate as many points as needed, but the curve must be accurate to 1 micron. 4. A written description of how to create (or a well commented C function for creating) a STEP AP203 bounding curve (face_outer_bound + edge_loop + oriented_edge + edge_curve) for both of the above surfaces. The edge is generated by a plane parallel to (but not coincident with) the axis of rotation of the surface. You may assume the ability to generate as many points as needed, but the curve must be accurate to 1 micron.