In my opinion, the SubD kernel should not compete with Mudbox, ZBrush, 3D-Coat, Claytools, or Sculptris. Rather, it should be optimized for designing outer surfaces of aircraft and boats. When you design these surfaces, you want lots of freedom, but you also want some constraints so that all engines fit inside the surfaces. It is natural to constrain the surfaces with curves. The ideal user interface would have 3 types of constraints:
- The surface must pass through entire constraining curve and it must satisfy chosen continuity at the curve (G0=kink, G1, or G2). Radio buttons provide additional options: start surface at the curve, terminate surface at the curve, close surface near the curve. Slider relaxes the surface (so that it is near the curve).
- The surface must be inside constraining curve. Slider pulls the surface away from the curve.
- The surface must be outside constraining curve. Slider pulls the surface away from the curve.