Sweep1 with the "Roadlike Top"option should create the desired surface for the example rail and curves based on the description in Rhino Help.
The shape curve maintains its angle to the Front construction plane throughout the sweep.
The shape curves in the attached example are all in planes normal to the Front construction plane. Unfortunately the shape curve using Sweep1 with the Roadlike Front option does not maintain its angle to the Front construction plane throughout the sweep. See the attached file for what it does. SweepQuestion2.3dm (42.7 KB)
Hi David - Roadlike … it does not mean the sections stay parallel to the selected plane, even though that is also a legitimate way to handle the sections - it is a little hard to describe other than ‘roadlke’ but here’s an image of some rectangles arrayed ‘roadlike;’ (red) and ‘freeform’ (cyan) on a wiggly curve- the original is on the right:
I probably should not have mentioned the mysterious “Roadlike”, too much of a distraction. I won’t mention it again in this thread.
[quote=“pascal, post:3, topic:33855”]
I think you can get what you want by -
ExtrudeCrv the path level with the Top plane.
Sweep1 along the edge of the surface using the ‘Align with surface’ style in sweep 1:
[/quote]That gives me what I want. Not at all obvious. Thanks. Much appreciated.
An option for the section/shape curve direction in Sweep1 and also in Sweep2 to use simple blending/interpolation of the section/shape based on the input section/shape curve direction only and not the shape of the rail(s) would be very useful. It is not at all obvious why in a simple sweep the shape/section curve wiggles around between the input shape/section curves.