Modeling 1: Polygons - An Introduction to Computer Graphics for Artists - page 73

Subdivision

This allows you to divide edges one or more times based on the number of evenly
divided cuts desired.

6.3.2.4 Bevel

If you invoke a bevel function with an edge selected, the selected edge will be
shaved from your object, usually at an angle perpendicular to the edge. Depending
on your options, you may get a straight cut or a smooth curve along the edge. Either
way, the result both blunts the edge and adds vertices to your model.

6.3.2.5 Smooth

This tool will perform a global bevel operation on every vertex of your model. The
result will multiply your poly count by four or more, and will make the model
smoother in appearance. This command is used to quickly add curve resolution to
character models, but this is not advised because at the same time as the command
increases curve resolution in your model, it also reduces detail in areas where you
want sharp angles to exist, and reduces the volume of the model.

6.3.2.6 Spline Creation

Spline creation tools are based on a device used in the shipbuilding and aircraft
industries by designers who needed a way to draw perfectly smooth curves with a
specifi c shape. To do this, they would put long strips of thin wood, the spline,
through slots in pegs on the fl oor of large design lofts. By adjusting the position and
rotation of the pegs, the shape of the spline was affected. Another type of spline
used weights to pull at curves by attaching them to a curve with string or wire. The
weight used would determine the strength of the effect. For computer graphics,
there are two primary types of spline, a normal spline, and a Bezier spline .
The types of spline are not as important at this stage of your introduction to CG
as your understanding that if you invoke a curve-creation tool, that you can draw a
smooth curve by clicking the points of the curve into existence. This is usually done
in an orthographic viewport, and then if necessary, the points of the curve are
adjusted in other viewports for truly three-dimensional curvature.
The reason you might want to build a polygonal object from a spline curve is that
a true spline can be evaluated mathematically at any point along its length, whether
or not it has a control point in that location. This makes curves both resolution
independent (because they can be split into any number of segments without affect-
ing the shape) and they are an easy way to align vertices along a carefully defi ned
curve (Fig. 6.4 ). This latter function is very diffi cult to imitate by hand, and
normally would not be attempted except for models that have an extremely low
level of curve resolution (fi ve vertices per arc or less).