rect_collision_study.pde

PVector a, b, as, bs;
void setup() {
  size(960, 540, P2D);
  smooth();
  colorMode(HSB, 360, 100, 100);
  blendMode(ADD);
  a = new PVector(200, 200);
  b = new PVector(400, 300);
  as = new PVector(random(10)-5, random(10)-5);
  bs = new PVector(random(10)-5, random(10)-5);
}

void draw() {
  background(0, 0, 0);

  rect(a.x, a.y, 100, 100);
  rect(b.x, b.y, 100, 100);

  if (a.x <= b.x +100 && b.x <= a.x +100 && a.y <= b.y +100 && b.y <= a.y +100) {      
      as.mult(-1);
      bs.mult(-1);
  }
  
  a.add(as);
  b.add(bs);

  if (a.x < 0 || a.x + 100 > width) {
    as.x *= -1;
  }
  if (b.x < 0 || b.x + 100 > width) {
    bs.x *= -1;
  }
  if (a.y < 0 || a.y + 100 > height) {
    as.y *= -1;
  }
  if (b.y < 0 || b.y + 100 > height) {
    bs.y *= -1;
  }
}