Modeling 1: Polygons - An Introduction to Computer Graphics for Artists - page 72

Fig. 6.3 Subdividing a cube adds vertices that can be used to alter its shape. On right , new faces
allow edge and vertex extrusion

overlaps the nearest pre-existing edge boundary, the new polygons it creates will
intersect (see Sect. 9.4.8 ) .

Face Extrude Around Edge

This command extrudes a face as in a normal extrude command, but does not cut a
selected edge out of the original geometry. The result is that all of the newly created
faces except two are rectangles, and the two that connect to the selected edge are
triangles. This creates a wedge-like shape that is useful for creating branching struc-
tures such as the limbs of a character.

6.3.2.3 Face Cutting

You may create new edges and vertices by cutting across faces. Most applications
have several tools that allow you to do this, some with greater control than others.
The simplest of these tools allows you to cut any face at any point along an edge by
clicking the edge where you want it to be cut. You will be expected to click on edges
belonging to either the same face or connected faces. This method is diffi cult to con-
trol with any accuracy, but there are other ways to cut faces that are more precise.

Controlled Cuts

A controlled cut allows the user to specify where along an edge the edge should be
cut. This can be done by typing in a percentage of the edge length, or by providing
a specifi c distance from a selected vertex. This can be done edge by edge to traverse
one or more faces.

Plane Cuts

A plane cut allows you to defi ne a plane and then cut through your entire model
along that plane wherever it intersects an edge on your model. This is a very handy
tool for creating a relationship among vertices on an irregular surface, like a parting
of hair on the skull.