1 files changed, 72 insertions, 0 deletions
diff --git a/Line.cpp b/Line.cpp
new file mode 100644
index 0000000..c755050
--- /dev/null
+++ b/Line.cpp
@@ -0,0 +1,72 @@
+#include "Line.h"
+#include <math.h>
+
+
+int lineIntersection(const LINE *la, const LINE *lb, Vertex *v) {
+  double xa1 = la->v1.getX(), ya1 = la->v1.getY();
+  double xa2 = la->v2.getX(), ya2 = la->v2.getY();
+  double xb1 = lb->v1.getX(), yb1 = lb->v1.getY();
+  double xb2 = lb->v2.getX(), yb2 = lb->v2.getY();
+  double temp;
+  int switched = 0;
+  Vertex v2;
+  
+  
+  if(!v) v = &v2;
+  
+  if(xa1 == xa2 && ya1 == ya2) return INTERSECTION_ERROR;
+  if(xb1 == xb2 && yb1 == yb2) return INTERSECTION_ERROR;
+  
+  if(xa1 == xa2 || xb1 == xb2) {
+    temp = xa1; xa1 = ya1; ya1 = temp;
+    temp = xa2; xa2 = ya2; ya2 = temp;
+    temp = xb1; xb1 = yb1; yb1 = temp;
+    temp = xb2; xb2 = yb2; yb2 = temp;
+    
+    switched = 1;
+  }
+  
+  if(xa1 == xa2 && xb1 == xb2)
+    return (xa1 == xb1) ? INTERSECTION_IDENTICAL : INTERSECTION_NONE;
+  
+  if(xa1 == xa2) {
+    v->setX(xa1);
+    v->setY(yb1);
+  }
+  else if(xb1 == xb2) {
+    v->setX(xb1);
+    v->setY(ya1);
+  }
+  else {
+    double ma = (ya2-ya1)/(xa2-xa1);
+    double mb = (yb2-yb1)/(xb2-xb1);
+    double ba = ya1 - ma*xa1;
+    double bb = yb1 - mb*xb1;
+    
+    if(ma == mb) return (ba == bb) ? INTERSECTION_IDENTICAL : INTERSECTION_NONE;
+    
+    v->setX((bb-ba)/(ma-mb));
+    v->setY(ma*v->getX() + ba);
+  }
+  
+  if(switched) {
+    temp = v->getX(); v->setX(v->getY()); v->setY(temp);
+    
+    //switch back everything for segment tests
+    temp = xa1; xa1 = ya1; ya1 = temp;
+    temp = xa2; xa2 = ya2; ya2 = temp;
+    temp = xb1; xb1 = yb1; yb1 = temp;
+    temp = xb2; xb2 = yb2; yb2 = temp;
+  }
+  
+  if(v->getX() < fmin(xa1,xa2) || v->getX() > fmax(xa1, xa2) || v->getY() < fmin(ya1,ya2) || v->getY() > fmax(ya1, ya2)) {
+    if(v->getX() < fmin(xb1,xb2) || v->getX() > fmax(xb1, xb2) || v->getY() < fmin(yb1,yb2) || v->getY() > fmax(yb1, yb2))
+      return INTERSECTION_LINE_LINE;
+    else
+      return INTERSECTION_LINE_SEGMENT;
+  }
+  else if(v->getX() < fmin(xb1,xb2) || v->getX() > fmax(xb1, xb2) || v->getY() < fmin(yb1,yb2) || v->getY() > fmax(yb1, yb2))
+    return INTERSECTION_SEGMENT_LINE;
+  else
+    return INTERSECTION_SEGMENT_SEGMENT;
+}