Bugs in Rhino 6 + suggestions for the BlendSrf command

The above post shows a good possibility to take advantage of the “Refine blend” option shown in the picture below, choosing between 3 possibilities: “Bezier surface” (automatic degree 5 with 6 control points), “Rebuild surface” (manual control) or “Minimum CP distance” (manual control):

Note that some options could be expanded or shrinked if necessary, in a similar fashion like the Rhino Options panel. That keeps the pop-up window as small as possible when the additional options are not used.

The “Use a guide rail” option lets you pick an existing curve or surface edge to influence the shape of the blend surface, sort of what the rail in “Sweep 2 rails” tool does. You can also pick multiple rails for the proposed “Blend surface” tool, including ones inside the blend surface (again, just like “Sweep 2 rail” lets you do).

The “Match target edge” option lets you pick the side edge of the target surface or an existing curve to match the tangent direction of the blend surface in that spot.

The “Bulge” option works in a similar fashion like the “Bulge” option of Rhino 8’s “Fillet surface” tool, allowing to modify the bulge influence of the blend surface (only when G2, G3 or G4 is used in at least one end of the surface).

The “Minimum CP distance” will prevent creation of a blend surface with gazzilion control points, because it lets you limit the distance between the closest control points. For example, settings a 3 mm “Minimum CP distance” for a blend surface whose shorter edge is 20 mm long will result into a surface with no more than 7 control points along the edge. In case that the shorter edge of the blend surface is 20 mm long and the user sets a “Minimum CP distance” of 25 mm, the blend surface will have just two control points, which is the bare minimum for a 4-sided surface to be created.

The “Match target isocurve U direction” and “Match target isocurve V direction” options let you swap the direction (either U or V) to avoid the typical bug in the current weak implementation of the "Match target isocurve direction"option found in “Match surface” that often gets confused and mixes both directions into one, leading to highly distorted unwanted results (sometimes even crashes Rhino).

Additionally, a new Command line option could be implemented, such like “Menu=Expanded” (expands all menus in the pop-up window) or “Menu=Compact” (closes the extra options to make the pop-up window similar to the current implementation). This command line option should be remembered for the current session.