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.
![](../image/topic_illustrations/extrusion-002.png)
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
![Not on toolbars.](../image/general/_no_toolbar_button.png)
UseExtrusions
Specify whether extrusion objects or polysurfaces are used when extruding straight‑sided objects.
The UseExtrusions command controls the use of extrusion objects.
- When UseExtrusions is turned on, Rhino commands that create simple solids and surfaces will use extrusion objects when possible.
- When UseExtrusions is turned off, Rhino will use surface and polysurface objects.
- Turning off UseExtrusions does not change existing extrusion objects.
![Not on toolbars.](../image/general/_no_toolbar_button.png)
ConvertExtrusion
Convert extrusion objects to surfaces and polysurfaces.
![Toolbar: Select Polysurfaces](../image/command_icons/selextrusion.png)
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.
![Toolbar: Curve Drawing | Geometry Fix | Main | Main2 | Popup | Solids Sidebar | Surface Sidebar](../image/command_icons/explode.png)
Explode
Break objects down into components.
Exploding an extrusion object results in an exploded a polysurface.
![Toolbar: Main | Main2 | Mesh Creation | Mesh Tools](../image/command_icons/mesh.png)
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.
![Toolbar: File | Popup | STL Tools](../image/command_icons/saveas.png)
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.
![Not on toolbars.](../image/general/_no_toolbar_button.png)
ConvertExtrusion
Convert extrusion objects to surfaces and polysurfaces.
Extrude curves
![Toolbar: Extrude | Extrude Solid | Solids Sidebar | Surface Creation | Surface Sidebar](../image/command_icons/extrudecrv.png)
ExtrudeCrv
Drive closed planar curves in a straight line.
![Toolbars: Extrude | Extrude Solid | Surface Creation | Surface Sidebar](../image/command_icons/extrudecrvalongcrv.png)
ExtrudeCrvAlongCrv
Drive closed planar curves along a path curve.
![Toolbars: Extrude | Extrude Solid | Surface Creation | Surface Sidebar](../image/command_icons/extrudecrvtapered.png)
ExtrudeCrvTapered
Drive closed planar curves in a straight line tapering at an angle.
![Toolbars: Extrude | Extrude Solid | Surface Creation | Surface Sidebar](../image/command_icons/extrudecrvtopoint.png)
ExtrudeCrvToPoint
Drive closed planar curves tapering to a point.
Extrude surfaces
![Toolbar: Extrude Solid | Solid Creation | Solids Sidebar](../image/command_icons/extrudesrf.png)
ExtrudeSrf
Drive surface edges in a straight line to create a solid.
![Toolbar: Extrude Solid](../image/command_icons/extrudesrfalongcrv.png)
ExtrudeSrfAlongCrv
Drive surface edges along a path curve to create a solid.
![Toolbar: Extrude Solid](../image/command_icons/extrudesrftapered.png)
ExtrudeSrfTapered
Drive surface edges in a straight line tapering at an angle to create a solid.
![Toolbar: Extrude Solid](../image/command_icons/extrudesrftopoint.png)
ExtrudeSrfToPoint
Drive surface edges tapering to a point to create a solid.
Draw extrusions
![Toolbar: Box | Main | Main1 | Solid Creation | Solids Sidebar](../image/command_icons/box.png)
Box
Draw a solid box.
![Toolbar: Solid Creation | Solids Sidebar](../image/command_icons/cylinder.png)
Cylinder
Draw a polysurface cylinder.
![Toolbar: Solid Creation | Solids Sidebar](../image/command_icons/pipe.png)
Pipe
Create a surface, polysurface, or extrusion object with a circular profile around a curve.
![Toolbar: Extrude Solid](../image/command_icons/slab.png)
Slab
Offset a polyline, and extrude and cap the result to create a solid.
Special case extrusions
![Toolbar: Extrude Solid](../image/command_icons/boss.png)
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.
![Toolbars: Extrude | Surface Creation | Surface Sidebar | Surface Creation | Surface Sidebar](../image/command_icons/fin.png)
Fin
Extrude a curve on a surface in the surface normal direction.
![Toolbar: Solid Creation | Solids Sidebar](../image/command_icons/pipe.png)
Pipe
Create a surface, polysurface, or extrusion object with a circular profile around a curve.
![Toolbar: Extrude Solid](../image/command_icons/rib.png)
Rib
Extrude a curve in two directions to a boundary surface.
![Toolbar: Extrude | Surface Creation | Surface Sidebar](../image/command_icons/ribbon.png)
Ribbon
Offset a curve and create a ruled surface between the curves.
![Toolbar: Extrude Solid](../image/command_icons/slab.png)
Slab
Offset a polyline, and extrude and cap the result to create a solid.