One of the features I really miss from 3DSMAX was the ability to rotate a a mesh object along a curve. This combined operation was much simpler than having to twist a finished object after it has been extruded along a curve. Any chance of including this in V6?
The Extrude commands keep the profile at the same angle it started at.
The Sweeps keep the profile at the same relationship to the rail curve. If the rail bends around, so do the profiles like a car following a road.
I should have been more specific. I meant that the rotation of the surface (or curve) is around its central axis, not relative to the rail or the curve that the surface is following. An example would be to create a Mobius strip in one operation. The rail or curve sets the circular path for the strip while the rotation imparts the one half twist that characterizes the Mobius strip.
OK, I’m tired of guessing.
Please post your curves and a description of the shape you expect to produce.
We’ll help with which commands and options to use.
I’d like to revive this if possible as I think i have the same question! Is there a method in Rhino, or through Grasshopper, to ‘ExtrudeSrfAlongCrv’, with the orientation of the extruded surface following perpendicular to the curve? This is the default mode of operation with ‘Sweep1’ and ‘RailRevolve’, but with ‘ExtrudeSrfAlongCrv’, the surface remains in it’s original XYZ orientation for the entire transformation. I assume one solution is to extract the edge curves individually but this adds some weight to my grasshopper definition!
Please find attached a volume modelled through ‘ExtrudeSrfAlongCrv’ (BLUE), overlaid with a ‘RailRevolve’ using the same base geometry (PINK).
My aim is to be able to animate compund transformations in Grasshopper, with the ‘swept volume’ of the original surface mapping the entire volume occupied by the surface over the duration.
I hope this is clearly explained enough, and many thanks for any advice!
You’re using the wrong commands. The “sweep” commands and components follow the rails. The “extrude” commands don’t sweep along the rails and are designed specifically to act that way.
I just made red surface (shown in the following screenshot) using Sweep2 command. This surface is very similar to the Mobius strip. The only difference is that it has 3 turns rather than 1 turn. The surface is a NURBS surface, but it can be easily converted to a (polygon) mesh.
The Sweep2 command makes a surface from two rails and at least one cross-section curve. The following screenshot shows these curves. I made blue circle first using Circle command. Next I made green helical spiral using Spiral command with AroundCurve option. I selected the blue curve in the AroundCurve option. The circle and the spiral were the rails in the Sweep2 command. The white line was the cross-section curve.
