Check the 4:30 minute in this video. Rhino lacks a very important option in the Command line:
“Direction=Horizontal” (to the Cplane)
I was forced to snap to the center of the vertical circle, as well as its quad. One small error with the snapping and this could get into a wrong direction.
In many cases, a horizontal direction is exactly what the users want, even on straight lines whole ends are not on the same Z level (like inclined lines). While extruding a line vertically by default is good for most of the applications, sometimes a horizontal extrusion is needed. A with a “Direction=Horizontal” option a straight line should be extruded to its normal direction along the XY coordinates.
The ! _Ribbon tool does something like that, but it will not preserve the structure of curves that are not straight lines. Instead, it creates an offset surface with a huge amount of control points and irregular shape rather than a straight extrusion.
Currently, there is only a single option for “Direction”, which requires manually written coordinates in the Command line or defining a directional vector by clicking with the mouse in the viewport.
One possible solution to calculate the median direction for curves other than straight lines “under-the-hood” is to create a loose curve offset and then define the extrusion direction manually by picking the middle points of both curves to create a straight extruded surface. This could be automated by Rhino, so that the user will not be forced to follow these steps manually just to get a horizontal direction for extrusion.
Horizontal extrusions of straight lines in normal direction along the XY coordinates of the CPlane (when you look at them from top view) could be made by using ! _Offset, then define the extrusion vector by snapping to the ends of both curves (the input one and the offset one).
