//https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles
public static FixVec3 ToEuler(FixQuaternion q)
{
FixVec3 result;
Fix t0 = 2 * (q.w * q.z + q.x * q.y);
Fix t1 = Fix.One - (2 * (q.y * q.y + q.z * q.z));
result._z = FixMath.Atan2(t0, t1);
Fix t2 = 2 * (q.w * q.y - q.z * q.x);
if (t2 >= Fix.One)
{
result._y = FixMath.PI / 2;
}
else if (t2 <= -Fix.One)
{
result._y = -(FixMath.PI / 2);
}
else
{
result._y = FixMath.Asin(t2);
}
Fix t3 = 2 * (q.w * q.x + q.y * q.z);
Fix t4 = Fix.One - (2 * (q.x * q.x + q.y * q.y));
result._x = FixMath.Atan2(t3, t4);
return(result);
}
//https://math.stackexchange.com/questions/2975109/how-to-convert-euler-angles-to-quaternions-and-get-the-same-euler-angles-back-fr
public static FixVec3 ToEuler(FixQuaternion q)
{
FixVec3 result;
Fix t0 = 2 * (q.w * q.z + q.x * q.y);
Fix t1 = 1 - 2 * (q.y * q.y + q.z * q.z);
result.z = FixMath.Atan2(t0, t1);
Fix t2 = 2 * (q.w * q.y - q.z * q.x);
if (FixMath.Abs(t2) >= Fix.one)
{
result.y = FixMath.PI / 2;
//t2 = 1;
}
else if (t2 <= -Fix.one)
{
result.y = -(FixMath.PI / 2);
//t2 = -1;
}
else
{
result.y = FixMath.Asin(t2);
}
Fix t3 = 2 * (q.w * q.x + q.y * q.z);
Fix t4 = 1 - 2 * (q.x * q.x + q.y * q.y);
result.x = FixMath.Atan2(t3, t4);
return(result);
}
//https://gamedev.stackexchange.com/questions/50963/how-to-extract-euler-angles-from-transformation-matrix
public FixVec3 EulerAngle()
{
FixVec3 ea = new FixVec3();
ea.x = FixMath.Atan2(-m[1, 2], m[2, 2]);
Fix cosYangle = FixMath.Sqrt(FixMath.Pow(m[0, 0], 2) + FixMath.Pow(m[0, 1], 2));
ea.y = FixMath.Atan2(m[0, 2], cosYangle);
Fix sinXangle = FixMath.Sin(ea.x);
Fix cosXangle = FixMath.Cos(ea.x);
ea.z = FixMath.Atan2((cosXangle * m[1, 0]) + (sinXangle * m[2, 0]), (cosXangle * m[1, 1]) + (sinXangle * m[2, 1]));
return(ea);
}