/**
Triangle-Triangle Intersection
Dave Bollinger
http://www.davebollinger.com

move primary triangle with mouse
right click to generate new secondary triangle

*/

Triangle2D sec;

void setup() {
  size(400,400,JAVA2D);
  smooth();
  build();
}

void build() {
  sec = new Triangle2D(
    random(width), random(height),
    random(width), random(height),
    random(width), random(height)
  );
}

void draw() {
  background(255);
  stroke(0);
  // build up some arbitrary irregular triangle around the mouse  
  Triangle2D pri = new Triangle2D(
    mouseX-50, mouseY+20,
    mouseX+30, mouseY-40,
    mouseX+40, mouseY+40
  );
  // set the fill color based on overlap status
  if (pri.overlaps(sec))  
    fill(255,0,0);
  else
    fill(0,255,0);
  // draw the triangles  
  sec.draw();
  pri.draw();
}

void mousePressed() {
  if (mouseButton==RIGHT)
    build();
}