Graphics Reference
In-Depth Information
Figure 3.9.
We begin by making the convex boundary from a list of vertices P
1
P
2
P
3
, and P
4
, defined
in a counter-clockwise sequence, which creates a corresponding chain of straight edges. As an
example, a quadrilateral has been chosen as shown in Fig. 3.10. We now need to find the general
form of the line equation for each boundary edge. If we do not apply a consistent algorithm,
we could end up with an incoherent collection of normal vectors.
Y
P
3
P
3
P
4
P
2
P
3
P
4
P
2
P
4
P
1
P
1
P
2
P
1
X
Figure 3.10.
We start with two points P
1
and P
2
that are the ends of an edge, as shown in Fig. 3.11.
