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Intersections

bool_point intersection_point (Point p0, Point p1, Point q0, Point q1) Static function
bool_point intersection_point (Point p0, Point p1, Point q0, Point q1, const bool trace) Static function
These functions find the intersection point, if any, of the lines determined by p0 and p1 on the one hand, and q0 and q1 on the other.

Let bp be the bool_point returned by intersection_point(). If an intersection point is found, the corresponding Point will be stored in bp.pt, otherwise, bp.pt will be set to INVALID_POINT. If the intersection point lies on both of the line segments, bp.b will be true, otherwise, false.

The two versions use different methods of finding the intersection point. The first uses a vector calculation, the second looks for the intersections of the traces of the lines on the major planes. If the trace argument is used, the second version will be called, whether trace is true or false. Ordinarily, there should be no need to use the trace version. 

          Point A(-1, -1);
          Point B(1, 1);
          Point C(-1, 1);
          Point D(1, -1);
          bool_point bp = Point::intersection_point(A, B, C, D);
          bp.pt.dotlabel("$i$");
          cout << "bp.b == " << bp.b << endl << flush;
          -| bp.b == 1


[Figure 94. Not displayed.]

Fig. 94. 

          Point A(.5, .5);
          Point B(1.5, 1.5);
          Point C(-1, 1);
          Point D(1, -1);
          bool_point bp = Point::intersection_point(A, B, C, D, true);
          bp.pt.dotlabel("$i$");
          cout << "bp.b == " << bp.b << endl << flush;
          -| bp.b == 0


[Figure 95. Not displayed.]

Fig. 95.