FloatArray hull = this.hull;
int size = hull.size;
float p1x = hull.get(size - 4);
float p1y = hull.get(size - 3);
float p2x = hull.get(size - 2);
float p2y = hull.peek();
return (p2x - p1x) * (p3y - p1y) - (p2y - p1y) * (p3x - p1x);
}
/** Sorts x,y pairs of values by the x value, then the y value.
* @param count Number of indices, must be even. */