/// <summary>
/// Subtracts the provided <see cref="quatf"/> from this
/// <see cref="quatf"/>.
/// </summary>
/// <param name="rhs">
/// The <see cref="quatf"/> to subtract from this
/// <see cref="quatf"/>.
/// </param>
/// <returns>
/// The resultant <see cref="quatf"/> from the subtraction.
/// </returns>
public quatf Subtract(quatf rhs)
{
var q = rhs;
return(new quatf(
-q.X * W + q.W * X + q.Z * Y - q.Y * Z,
-q.Y * W - q.Z * X + q.W * Y + q.X * Z,
-q.Z * W + q.Y * X - q.X * Y + q.W * Z,
q.W * W + q.X * X + q.Y * Y + q.Z * Z));
}
/// <summary>
/// Converts an orientation represented as a quaternion to a
/// direction cosine matrix.
/// </summary>
/// <param name="quat">
/// The quaternion to convert.
/// </param>
/// <returns>
/// The corresponding direction cosine matrix.
/// </returns>
public static mat3f Quat2Dcm(quatf quat)
{
var q1 = quat.X;
var q2 = quat.Y;
var q3 = quat.Z;
var q0 = quat.W;
return(new mat3f(
q0 * q0 + q1 * q1 - q2 * q2 - q3 * q3,
2f * (q1 * q2 + q0 * q3),
2f * (q1 * q3 - q0 * q2),
2f * (q1 * q2 - q0 * q3),
q0 * q0 - q1 * q1 + q2 * q2 - q3 * q3,
2f * (q2 * q3 + q0 * q1),
2f * (q1 * q3 + q0 * q2),
2f * (q2 * q3 - q0 * q1),
q0 * q0 - q1 * q1 - q2 * q2 + q3 * q3));
}
/// <summary>
/// Creates a new <c>AttitudeF</c> from a quaternion.
/// </summary>
/// <param name="quat">
/// The orientation expressed as a quaternion.
/// </param>
/// <returns>
/// The new <c>AttitudeF</c>.
/// </returns>
public static AttitudeF FromQuat(quatf quat)
{
return(new AttitudeF(AttitudeType.Quat, quat));
}
