Graphics Programs Reference
In-Depth Information
In this exercise, you used the geometric constraint as an editing tool to move an object into
an exact location. The concentric constraint will also keep the circle inside the arc no matter
where the arc moves.
THE ORDER MAKES A DIFFERENCE
When you add constraints, sometimes the order in which you add them makes an important dif-
ference. In the concentric constraint example, you selected the arc first, and then the circle. Had
you selected the circle first, the arcs and lines would have moved to the circle. Instead, as you saw
in the exercise, the circle moved to the inside of the arc.
Using Other Geometric Constraints
You've seen firsthand how several of the geometric constraints work. For the most part, each con-
straint is fairly easy to understand. The tangent constraint keeps objects tangent to each other. The
coincident constraint keeps the location of objects together, such as endpoints or midpoints of
lines and arcs. The parallel constraint keeps objects parallel.
There are many more geometric constraints you have at your disposal. Table 16.1 gives you a
concise listing of the constraints (in order of appearance in the menus) and their purposes. Note
that with the exception of fix and symmetric, all of the constraints affect pairs of objects.
TABLE 16.1:
The geometric constraints
NAME
USE
Coincident
Keeps point locations of two objects together, such as the endpoints or midpoints of
lines. Allowable points vary between objects and are indicated by a red circle marked
with an
X
while points are being selected.
Collinear
Keeps lines collinear. The lines need not be connected.
Concentric
Keeps circles and arcs concentric.
Fix
Fixes a point on an object to a location in the drawing.
Parallel
Keeps lines parallel.
Perpendicular
Keeps lines or polyline segments perpendicular.
Horizontal
Keeps lines horizontal.
Ver t ic al
Keeps lines vertical.
Tan gent
Keeps curves, or a line and curve, tangent to each other.
Smooth
Maintains a smooth transition between splines and other objects. The first object selected
must be a spline. You can think of this const raint as a tangent const raint for splines.
