Function xsqrtfast

src/SB/Core/x/xCollide.cpp:1567–1570

        guess = 0.5 * guess * -(guess * guess * x - 3);
        guess = 0.5 * guess * -(guess * guess * x - 3);
        guess = 0.5 * guess * -(guess * guess * x - 3);
        return x * guess;
    }
    else
    {
        return x;
    }