Sweep generation curves along rail curves (Rail)

Create a surface by calculating the area swept out by a generation curve moving along one or more rail curves. You can use one generation curve or blend between two or more generation curves.

Choose Surfaces > Swept Surfaces > Rail Surface ❒.
In the option window, set the number of Generation Curves and Rail Curves you have.
Click the generation curve or curves. To deselect a generation curve, click it again.
If you chose 2+ generation curves, click Go when you are finished selecting generation curves.
Click the rail curve or curves.

Maintain continuity with other surfaces

In the Rail Control window, use the pop-up menus next to the names of the generation and rail curves to choose what type of continuity you want along that edge.

What if...?

I can’t create a surface from my curves?

Make sure your curves intersect. If modifications to the boundary curves cause them to stop intersecting (while construction history is on), a small red and yellow arrow appears at that corner. Right mouse clicking on the arrow displays a bubble with an explanation of the problem.

See Make curves intersect.
The Rail Surface tool tests whether curves intersect within the Curve Fit Distance tolerance in Construction Options. To change the Curve Fit Distance option, choose Preferences > Construction Options.
You can’t create a surface along rail curves with sharp corners, CV multiplicity, or multi-knots. To remove multi-knots, turn on the Rebuild option for rail curves.

The surface is created away from the rails?

It is the generation curve’s pivot point that travels along the rail curve. If the pivot point is not on the generation curve, the new surface will be offset.

See Change an object’s pivot point.

The resulting surface is too complex?

Turn on the Rebuild options for the curves used to create the surface.
Turn on the Explicit control option, then manually choose how many spans the surface may have and what degree it should be in the U and V directions.

I want to change a rail surface after I’ve worked on other objects?

Choose Object Edit > Query Edit and click the surface.

See View and edit the construction history of an object.