static void ToAxisAngleRad(Quaternion q, out Vector3 axis, out float angle)
{
if (Mathf.Abs(q.w) > 1.0f)
{
q.Normalize();
}
angle = 2.0f * (float)Mathf.Acos(q.w); // angle
float den = (float)Mathf.Sqrt(1.0f - q.w * q.w);
if (den > 0.0001f)
{
axis = q.xyz / den;
}
else
{
// This occurs when the angle is zero.
// Not a problem: just set an arbitrary normalized axis.
axis = new Vector3(1, 0, 0);
}
}
/// <summary>
/// Assumes that the axis is UnitZ and calculates the euler angle.
/// </summary>
/// <param name="q"></param>
/// <returns></returns>
public static float AngleFromQuaternionUnitZ(Quaternion q)
{
q.Normalize();
// Quaternions don't remember our initial rotation axis. Quaternion.Angle always returns values in the range [0,PI).
return(q.Angle * (q.Axis.Z >= 0 ? 1 : -1));
}
