The Linear Extrusion filter is a modeling filter that takes polygonal data as input and generates polygonal data on output. The input data set is swept according to some extrusion function and creates new polygonal primitives. These primitives form a "skirt" or swept surface. For example, sweeping a line results in a quadrilateral, and sweeping a triangle creates a "wedge".
There are a number of control parameters for this filter. You can control whether the sweep of a 2D object (i.e., polygon or triangle strip) is capped with the generating geometry. Also, you can extrude in the direction of a user specified vector, towards a point, or in the direction of vertex normals . The amount of extrusion is controlled by the scale factor.
The skirt is generated by locating certain topological features. Free edges (edges of polygons or triangle strips only used by one polygon or triangle strips) generate surfaces. This is true also of lines or polylines. Vertices generate lines.
This filter can be used to create 3D fonts, 3D irregular bar charts, or to model 2 1/2D objects like punched plates. It also can be used to create solid objects from 2D polygonal meshes.
Some polygonal objects have no free edges (e.g., sphere). When swept, this will result in two separate surfaces if capping is on, or no surface if capping is off.