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 plenty of memory is available.
The UseExtrusions command controls the use of lightweight extrusion objects. To make commands like Box, Cylinder, Pipe, and ExtrudeCrv create lightweight extrusion objects, run UseExtrusions and choose the Extrusions option. To make commands to create traditional polysurfaces, select the Polysurface option.
Extrusion objects consist of a profile curve and a distance and will only display three control points.
UseExtrusions: This command lets you control the use of extrusion objects. When extrusion use is turned on, Rhino commands that create simple solids and surfaces will use extrusion objects when possible. When extrusion use is turned off, Rhino will use traditional surface and polysurface objects. Turning off extrusion use does not change existing extrusion objects.
SelExtrusions: Selects extrusion objects. It will not select polysurface or surface objects. You can use this command if you really want to see which objects are extrusion objects.
ConvertExtrusion: Converts extrusions to traditional polysuface or surface objects. You can choose to either replace the existing extrusions or add the converted objects.
Dir: Extrusion objects work like polysurfaces and surfaces.
SelPolySrf, SelOpenPolySrf, SelClosedPolySrf: Select extrusion objects that look and act like traditional polysurface objects.
SelSrf, SelClosedSrf, SelOpenSrf: Select extrusion objects that look and act like traditional surfaces.
ExtrudeCrv: Create lightweight extrusion objects when possible.
Box, Cylinder, Tube: Create lightweight extrusion objects.
Pipe, Slab: Create lightweight extrusion objects when possible.
Explode: Exploding an extrusion object results in an exploded a polysurface.
Mesh: The walls are always meshed with quads running the length of the extrusion. The caps are generally meshed with triangles.
SaveAs V4: Extrusion objects are converted to polysurfaces when saving as V4 files.