@Override
 public Vec2f getMax(Vec2f max) {
   if (max == null) {
     max = new Vec2f();
   }
   max.x = maxX;
   max.y = maxY;
   return max;
 }
 @Override
 public Vec2f getMin(Vec2f min) {
   if (min == null) {
     min = new Vec2f();
   }
   min.x = minX;
   min.y = minY;
   return min;
 }