private void AddCurvePosition (float p, float x1, float y1, float cx1, float cy1, float cx2, float cy2, float x2, float y2,
float[] output, int o, bool tangents) {
if (p == 0 || float.IsNaN(p)) p = 0.0001f;
float tt = p * p, ttt = tt * p, u = 1 - p, uu = u * u, uuu = uu * u;
float ut = u * p, ut3 = ut * 3, uut3 = u * ut3, utt3 = ut3 * p;
float x = x1 * uuu + cx1 * uut3 + cx2 * utt3 + x2 * ttt, y = y1 * uuu + cy1 * uut3 + cy2 * utt3 + y2 * ttt;
output[o] = x;
output[o + 1] = y;
if (tangents) output[o + 2] = (float)Math.Atan2(y - (y1 * uu + cy1 * ut * 2 + cy2 * tt), x - (x1 * uu + cx1 * ut * 2 + cx2 * tt));
}
}