/// <summary>
/// angle of two vector
/// </summary>
/// <param name="first">First.</param>
/// <param name="second">Second.</param>
public static float Angle(UVector3 first, UVector3 second)
{
return((float)System.Math.Acos((UVector3.Dot(first, second)) / (first.magnitude * second.magnitude))
* MathHelper.Rad2Deg);
}
/// <summary>
/// Do Spherical linear interpolation between two quaternions
/// </summary>
/// <param name="q1">The first quaternion</param>
/// <param name="q2">The second quaternion</param>
/// <param name="blend">The blend factor</param>
/// <returns>A smooth blend between the given quaternions</returns>
public static UQuaternion Slerp(UQuaternion q1, UQuaternion q2, float blend)
{
// if either input is zero, return the other.
if (q1.LengthSquared == 0.0f)
{
if (q2.LengthSquared == 0.0f)
{
return(identity);
}
return(q2);
}
else if (q2.LengthSquared == 0.0f)
{
return(q1);
}
float cosHalfAngle = q1.w * q2.w + UVector3.Dot(q1.Xyz, q2.Xyz);
if (cosHalfAngle >= 1.0f || cosHalfAngle <= -1.0f)
{
// angle = 0.0f, so just return one input.
return(q1);
}
else if (cosHalfAngle < 0.0f)
{
q2.Xyz = -q2.Xyz;
q2.w = -q2.w;
cosHalfAngle = -cosHalfAngle;
}
float blendA;
float blendB;
if (cosHalfAngle < 0.99f)
{
// do proper slerp for big angles
float halfAngle = (float)System.Math.Acos(cosHalfAngle);
float sinHalfAngle = (float)System.Math.Sin(halfAngle);
float oneOverSinHalfAngle = 1.0f / sinHalfAngle;
blendA = (float)System.Math.Sin(halfAngle * (1.0f - blend)) * oneOverSinHalfAngle;
blendB = (float)System.Math.Sin(halfAngle * blend) * oneOverSinHalfAngle;
}
else
{
// do lerp if angle is really small.
blendA = 1.0f - blend;
blendB = blend;
}
var result = new UQuaternion(
blendA * q1.Xyz + blendB * q2.Xyz,
blendA * q1.w + blendB * q2.w);
if (result.LengthSquared > 0.0f)
{
return(Normalize(result));
}
else
{
return(identity);
}
}