Surfaces are like a thin sheet of paper that define any shape in 3D space. They are NURBS objects and are great when the end goal is manufacturing. You can create surfaces from primitives such as the Plane or Sphere or from a freeform surface command. In this chapter, we will explore the surfacing commands that require curves as input.

Surface from Edge Curves

You can create a surface from three or four curves that define the edges of the surface.

To create a surface from edge curves:

1. Open EdgeSrf.3dm in Rhino .
2. From the Surface menu, run the EdgeSrf command.
3. At the Select 2, 3, or 4 open curves prompt , select the four curves as shown in the illustration below.

Extrude Curves

Surfaces can be created by extruding curves in a straight line perpendicular to the construction plane.

To create an extruded surface:

1. Open ExtrudeCrv.3dm in Rhino .
2. Run the ExtrudeCrv command.
3. At the Select curves to Extrude prompt , select all black curves and press Enter or right-click.
4. At the Extrusion distance prompt , type 30.

Loft Curves

Loft creates a smooth surface that blends between selected curves. The curves define “ribs” for the surface you are creating.

To create a lofted surface:

1. Open Loft.3dm in Rhino .
2. From the Surface menu, run the Loft command.
3. At the Select curves to loft prompt , window-select all curves and press Enter .
4. In the Loft dialog box, click the drop-down menu under Style. The default is Normal. Try Loose or Straight Sections to see the different results. Click OK when done.

Revolve Curves

Revolve creates a surface by revolving curves about a revolve axis. The curve defines the silhouette of the revolved surface. This action is sometimes called lathing in other programs.

To create a revolved surface:

1. Open Revolve.3dm in Rhino .
2. From the Surface menu, run the Revolve command.
3. At the Select curves to revolve prompt , select the red curve and press Enter .
4. At the Start of revolve axis prompt , type 0 and press Enter . It will snap to the center of the grid.

1. At the End of revolve axis prompt , press Enter to use the Cplane z-axis direction as an axis.
2. At the Start angle prompt click on the FullCircle Command Line option.

Revolve Curves with a Rail

RailRevolve creates a surface by revolving a profile curve while following a rail curve as closely as possible. The profile curve defines the silhouette of the surface, and the rail curve defines a path the profile curve will try to follow.

To create a revolved surface around a rail curve:

1. Open RailRevolve.3dm in Rhino .

1. From the Surface menu, run the RailRevolve command.
2. At the Select profile curve prompt , select the red curve.
3. At the Select rail curve prompt , select the black curve.
4. At the Start of RailRevolve axis prompt , type 0.
5. At the End of RailRevolve axis prompt , press Enter to use the Cplane z-axis direction as an axis.

1. Select the resulting object.
2. Run the Cap command to close it.

Sweep Along One Rail

Sweep1 creates a smooth surface from one or multiple cross-section curves and a single rail curve. The cross-section curves define the surface shape, and the rail curve defines the path the surface will follow.

To create a sweep surface with a rail curve:

1. Open Sweep1.3dm in Rhino
2. From the Surface menu, run the Sweep1 command.
3. At the Select rail prompt , select the black curve.
4. At the Select sweep shapes prompt , select the red curves one by one and press Enter when done.

1. At the Drag seam point to adjust… prompt click the Natural option in the Command Prompt . This will align the arrows on the same starting point for all the sections. Press Enter .
2. In the Sweep 1 Rail Options dialog box, click OK. The default Freeform will be used.
3. Change the Display Mode to Monochrome.

Sweep Along Two Rails

Sweep2 creates a smooth surface from one or multiple cross-section curves and two rail curves. The cross-section curves define the surface shape, and the rail curves define the path the two edges of the surface will follow as closely as possible.

To create a sweep surface with two rail curves:

1. Open Sweep2.3dm in Rhino .

1. From the Surface menu, run the Sweep2 command.
2. At the Select first rail prompt , select one of the black curves. The order doesn’t matter.
3. At the Select second rail prompt , select the second black curve.
4. At the Select sweep shapes prompt , select the two red curves one by one. The order doesn’t matter.
5. Press Enter twice.
6. In the Sweep 2 Rail Options dialog box, click OK. No further adjustments will be needed in this case.
7. Change the Display Mode to Monochrome or Arctic to get a better understanding of shape.

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