Development Plan

Ready (for cubics, partial weight support):

• FreeCAD Sketcher as interface to define NURBS control polygons.
• Control Polygon Objects linked to Sketch(es)
• Cubic Curve object linked to Control Polygons
• Grid objects linked to loops of 3 or 4 Control Polygons (3 curves results in a degenerate grid)
• Surface objects linked to grid objects
• subdividing/segmenting curve and surface objects
• 2 curve corner blending with automatic G2 output
• 2 face seam blending with automatic G2 output
• methods to tune corner and seam blends (G3+ output is sometimes possible)
• method to blend the corner formed by 3 faces (includes a degenerate surface OR aFreeCAD Surface workbench 'Filling' surface, impact can sometimes be minimized)
• method to blend the corner formed by 5 faces (includes a FreeCAD Surface workbench 'Filling' surface, impact can sometimes be minimized)
• cap N sided fillet with non degenerate NStar by joining of N quadrangles. This is intended to fill small holes that are nearly flat. This NStar is G2 to the edges of the hole, but has a serious defect in the center of the star. Use to quickly fill 3, 5, 6...N sided holes between blended edges. These are not high quality constructions, but they may be useful to 'rough in' a blended design before applying more refined techniques.

Needed:

• convenience: more point on curve methods (at curve intersection, surface intersection, etc)
• convenience: point on surface methods
• convenience: more segmenting methods
• modeling tool: isoline extraction
• modeling tool: crude normal offset. maintains order and pole count.
• core function: a fully G2 "NRing" of surfaces to reduce the size of the hole to fill with an NStar. [exists, but not useful enough yet]
• core function: automatic G3 'seeking' for 6 point poly based curves and surfaces. This function can probably use a numerical method instead of an exact algebraic solution. [exists, but is rarely useful]
• modeling tool: add control points to curves and surfaces to give additional design freedom away from the seams (more flexibility in basic/unblended surface design). This is easy to do for curves, but it is not easy to make surfaces from these curves.
• core function: raise degree as needed to improve continuity, both at the seams, and at internal knots.