/* Approximates the integral which uses the arclength and curvature of the parabola.  */
static vg_lite_float_t approx_integral(vg_lite_float_t x)
/* Approximates the integral which uses the arclength and curvature of the parabola.  */
static vg_lite_float_t approx_integral(vg_lite_float_t x)
{
    const vg_lite_float_t D = 0.67;
    return x / (1.0 - D + FPOWF(FPOWF(D, 4) + 0.25 * x * x, 0.25));
}