Extrude curves and surfaces

Extrudes use a base curve or surface to make an open or closed shape. Extrusions can be polysurfaces or lightweight extrusion objects.


Polysurfaces (red); extrusion objects (blue).

Lightweight extrusion objects

Light-weight extrusion objects use only a profile curve and a length as input instead of the network of isocurves normally needed for NURBS objects. The Box, Cylinder, Tube, ExtrudeCrv, and ExtrudeSrf commands create extrusion objects. Extrusion objects can be closed with a planar cap or open. These objects will be converted to polysurfaces by some commands if necessary to add additional information for editing.

Lightweight extrusion objects use less memory, mesh faster, and save smaller than the traditional polysurfaces.

In models containing large numbers of extrusions represented by traditional polysurfaces, performance can be sluggish due to the relatively high demand on resources. If the same objects are made in Rhino as lightweight extrusion objects, these models are more responsive and more memory is available.

The UseExtrusions command controls the use of lightweight extrusion objects. To make commands that normally create extrusions create traditional polysurfaces, select the Polysurface option.

Commands affected

UseExtrusions

Specify whether extrusion objects or polysurfaces are used when extruding straight‑sided objects.

The UseExtrusions command controls the use of extrusion objects.

ConvertExtrusion

Convert extrusion objects to surfaces and polysurfaces.

SelExtrusion

Select Extrusion objects.

The SelExtrusion command will not select polysurface or surface objects. Use this command if you want to see which objects are extrusion objects.

Explode

Break objects down into components.

Exploding an extrusion object results in an exploded a polysurface.

Mesh

Create a mesh from a NURBS surface or polysurface.

The walls of extrusion objects are always meshed with quadrangles running the length of the extrusion. The caps are generally meshed with triangles.

SaveAs

Save the current model with a different name, close the current model, and open the new model.

Extrusion objects are converted to polysurfaces when saving as Rhino 4 or earlier.

ConvertExtrusion

Convert extrusion objects to surfaces and polysurfaces.

Extrude curves

ExtrudeCrv

Drive closed planar curves in a straight line.

ExtrudeCrvAlongCrv

Drive closed planar curves along a path curve.

ExtrudeCrvTapered

Drive closed planar curves in a straight line tapering at an angle.

ExtrudeCrvToPoint

Drive closed planar curves tapering to a point.

Extrude surfaces

ExtrudeSrf

Drive surface edges in a straight line to create a solid.

ExtrudeSrfAlongCrv

Drive surface edges along a path curve to create a solid.

ExtrudeSrfTapered

Drive surface edges in a straight line tapering at an angle to create a solid.

ExtrudeSrfToPoint

Drive surface edges tapering to a point to create a solid.

Draw extrusions

Box

Draw a solid box.

Cylinder

Draw a cylinder.

Pipe

Create a surface, polysurface, or extrusion object with a circular profile around a curve.

Slab

Offset a polyline, and extrude and cap the result to create a solid.

Special case extrusions

Boss

Extrude closed planar curves normal to the curve plane toward a boundary surface where the boundary surface is trimmed and joined to the extruded objects.

Fin

Extrude a curve on a surface in the surface normal direction.

Pipe

Create a surface, polysurface, or extrusion object with a circular profile around a curve.

Rib

Extrude a curve in two directions to a boundary surface.

Ribbon

Offset a curve and create a ruled surface between the curves.

Slab

Offset a polyline, and extrude and cap the result to create a solid.

See also

Polysurfaces

 

 

 

Rhinoceros 6 © 2010-2019 Robert McNeel & Associates. 16-Jul-2019