This is how I make surface blends in Rhino:
Duplicate edge curves
Turn on edit points
Extract isocurves at edit points locations
Make a 2 Rail Sweep
This results in a nice single-span, up to G4 continuous blend surface and relates to the GH Blend Surface definition post I wrote previously.
I might be wrong, but it seems to me that this method produces better results than making the usual 2 rail sweep and then running a surface match command.
Indeed, matching the surface breaks G2 continuity at the naked edges and even at the internal cross sections end points, even if I set the ‘Isocurve Direction Adjustment’ to ‘Automatic’ in the Match Surface options window.
So my questions are:
Shouldn’t the match command try to achieve a ‘natural’ isocurve direction when set to automatic?
It seems intuitive that two surfaces have G2 continuity at one edge if their isocurves are G2 continuous, am I wrong?