float atan2Approximation for C# and Shader

atan2Approximation.cs

// c#
float atan2Approximation(float y, float x) // http://http.developer.nvidia.com/Cg/atan2.html
{
	float t0, t1, t2, t3, t4;
	t3 = Mathf.Abs(x);
	t1 = Mathf.Abs(y);
	t0 = Mathf.Max(t3, t1);
	t1 = Mathf.Min(t3, t1);
	t3 = 1f / t0;
	t3 = t1 * t3;
	t4 = t3 * t3;
	t0 =         - 0.013480470f;
	t0 = t0 * t4 + 0.057477314f;
	t0 = t0 * t4 - 0.121239071f;
	t0 = t0 * t4 + 0.195635925f;
	t0 = t0 * t4 - 0.332994597f;
	t0 = t0 * t4 + 0.999995630f;
	t3 = t0 * t3;
	t3 = (Mathf.Abs(y) > Mathf.Abs(x)) ? 1.570796327f-t3 : t3;
	t3 = (x < 0) ? 3.141592654f-t3:t3;
	t3 = (y < 0) ? -t3 : t3;
	return t3;
}

// shader
float atan2Approximation(float y, float x) // http://http.developer.nvidia.com/Cg/atan2.html
{
	float t0, t1, t2, t3, t4;
	t3 = abs(x);
	t1 = abs(y);
	t0 = max(t3, t1);
	t1 = min(t3, t1);
	t3 = float(1) / t0;
	t3 = t1 * t3;
	t4 = t3 * t3;
	t0 =         - 0.013480470;
	t0 = t0 * t4 + 0.057477314;
	t0 = t0 * t4 - 0.121239071;
	t0 = t0 * t4 + 0.195635925;
	t0 = t0 * t4 - 0.332994597;
	t0 = t0 * t4 + 0.999995630;
	t3 = t0 * t3;
	t3 = (abs(y) > abs(x)) ? 1.570796327 - t3 : t3;
	t3 = (x < 0) ?  3.141592654 - t3 : t3;
	t3 = (y < 0) ? -t3 : t3;
	return t3;
}