Graphics Programs Reference
In-Depth Information
Splines and helixes
Splines are smooth linear objects, normally without corners that pass through or
near specified points. Spline is short for
Nonuniform Rational B-Spline
(
NURBS
).
Splines are described by a set of parametric mathematical equations, but have no
fear, for AutoCAD will internally deal with this, we will not have to!
Splines are used whenever we need smooth curves and are also the foundation for
NURBS surfaces, the most used surfaces in the automotive or aeronautic projects.
To create a spline we apply the (guess?)
SPLINE
command (alias
SPL
). By default,
the command only prompts for the location of fit points, and the spline passes
through the specified points. An
Enter
finishes the spline and the
Close
option cre-
ates a closed spline.
We can control splines by two sets of vertices:
•
Fit points
: These are the points used to create the spline
•
Control vertices
: These are the points that define the spline
When selected, the small blue triangle allows switching between
Fit points
and
Control vertices
. To edit a spline is very simple: we select it, without command,
and work with grips. We can either click a grip and move it, or we can place the curs-
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