public static Quaternion Nlerp( Real fT, Quaternion rkP, Quaternion rkQ, bool shortestPath )
{
Quaternion result;
var fCos = rkP.Dot( rkQ );
if ( fCos < 0.0f && shortestPath )
{
result = rkP + fT*( ( -rkQ ) - rkP );
}
else
{
result = rkP + fT*( rkQ - rkP );
}
result.Normalize();
return result;
}
/// <summary>
///
/// </summary>
/// <param name="time"></param>
/// <param name="quatA"></param>
/// <param name="quatB"></param>
/// <param name="useShortestPath"></param>
/// <returns></returns>
public static Quaternion Slerp( Real time, Quaternion quatA, Quaternion quatB, bool useShortestPath )
{
var cos = quatA.Dot( quatB );
var angle = (Real)Utility.ACos( cos );
if ( Utility.Abs( angle ) < EPSILON )
{
return quatA;
}
var sin = Utility.Sin( angle );
var inverseSin = 1.0f/sin;
var coeff0 = Utility.Sin( ( 1.0f - time )*angle )*inverseSin;
var coeff1 = Utility.Sin( time*angle )*inverseSin;
Quaternion result;
if ( cos < 0.0f && useShortestPath )
{
coeff0 = -coeff0;
// taking the complement requires renormalisation
var t = coeff0*quatA + coeff1*quatB;
t.Normalize();
result = t;
}
else
{
result = ( coeff0*quatA + coeff1*quatB );
}
return result;
}