Polysurfaces and extrusion objects

A polysurface consists of two or more surfaces that are joined together. A polysurface that encloses a volume of space defines a solid.

Solids are created anytime a surface or polysurface is completely closed.

Some Rhino commands create polysurface solids. Pyramid, Cone, and TruncatedCone are examples of commands that create polysurface solids.

Lightweight extrusion objects

The Box, Cylinder, Tube, ExtrudeCrv, and ExtrudeSrf commands can create polysurface or extrusion objects. Polysurfaces can be closed with a planar cap or open.

Note

In models containing large numbers of 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.

When UseExtrusions is turned on, Rhino commands that create simple solids and surfaces will use extrusion objects when possible.
When UseExtrusions is turned off, these commands will create surface and polysurface objects.
Turning off UseExtrusions does not change existing extrusion objects.

ConvertExtrusion

Convert extrusion objects to surfaces and polysurfaces.

SelPolysrf

Select all polysurfaces.

SelClosedPolysrf

Select all closed polysurfaces.

SelOpenPolysrf

Select all open polysurfaces.

Explode

Break objects down into components.

ConvertExtrusion

Convert extrusion objects to surfaces and polysurfaces.

Draw polysurfaces

When UseExtrusions is turned off, these commands will create surface and polysurface objects.

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.