Sweep1

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Surface Creation Surface Sidebar	Surface Sweep 1 Rail

The Sweep1 command fits a surface through a series of profile curves that define the surface cross-sections and one curve that defines a surface edge.

Steps

Select a single rail curve.
Select cross-section curves in the order that the surface will pass through them.
When multiple closed cross-section curves are selected, there will be an extra step for adjusting curve seams.

Tips

Cross-section curves with the same structure create a better sweep surface. Cross-section curves will have the same structure if they are all copied from the same curve.
If the cross-section curves do not have the same structure, use the Rebuild cross sections or Refit cross sections options. The rebuilt or refitted copies of the cross-section curves will be used to sweep.
When Refit rail is enabled, the refitting tolerance is controlled by Document Properties -> Units -> Absolute tolerance.

Command-line options
ChainEdges (rails only)	Select connected edge/curve segments based on the continuity between segments. How to chain selection.
Point (cross‑sections only)	Creates a surface that begins or ends at a point.

Command-line options

ChainEdges
(rails only)

Select connected edge/curve segments based on the continuity between segments.

How to chain selection.

Point
(cross‑sections only)

Creates a surface that begins or ends at a point.

Adjust seam options (Closed curves only)

Flip

Reverses the curve direction.

Automatic

Attempts to align the seam points and directions without intervention.

Natural

Moves the seam points to the way they were at the beginning of the command.

To adjust seams

Select each seam point and move it along the curve to line up all curve seams.
Use the Flip option to make all seam arrows point to the same side.
Press Enter to continue.

Frame Style

A frame is a 3-D point and three direction vectors. It can be drawn as something that looks like the Rhino world axes icon. It describes a unique coordinate system in space. Frames are calculated along the rail and are used to orient the cross-section curves at those locations. In a simple case with one cross-section, frames are made at the cross-section curve location and where the calculated cross-section is going to go. The 3-D rotation between those two frames determines the rotation of the cross-section curve at its new location.

Freefrom is the default Frame style. The selected Frame style will be remembered in the current Rhino for next use.

Freeform

Roadlike

Specify an axis for calculating the 3-D rotation of the cross-section.

The default Roadlike axis will be different depending on the rail curve. For a planar rail curve, the default axis is perpendicular to the curve plane. For a non-planar rail curve, world-Z axis will be used.

Set axis

Sets the axis direction for the Roadlike style.

Align with surface (surface edge as rail only)

Sweep options

Closed sweep

Global shape blending

The sweep is linearly blended from one end to the other, creating sweeps that taper from one cross-section curve to the other. Otherwise, the sweep stays constant at the ends and changes more rapidly in the middle.

Global shape blending on.

Global shape bending off.

Untrimmed miters

Curve options

Refit rail

Do not change cross sections

Rebuild cross sections with ___ control points

Refit cross sections within ___

Technical notes

To determine the movement of a cross-section, one frame is found at an existing cross-section location and another is calculated at the desired location along the rail. The difference between those frames defines the movement of the cross-section.

If the rail tangent and the arbitrary vector are parallel, they do not define a plane and the cross product does not produce a vector, so the frame is under-defined, and it will twist around the rail tangent since that is the only defined information.