/// <summary>
/// Convert this instance to an axis-angle representation.
/// </summary>
/// <returns>A Vector4 that is the axis-angle representation of this quaternion.</returns>
public SCNVector4 ToAxisAngle()
{
SCNQuaternion q = this;
if (q.W > 1.0f)
{
q.Normalize();
}
SCNVector4 result = new SCNVector4();
result.W = 2.0f * (pfloat)System.Math.Acos(q.W); // angle
pfloat den = (pfloat)System.Math.Sqrt(1.0 - q.W * q.W);
if (den > 0.0001f)
{
result.Xyz = q.Xyz / den;
}
else
{
// This occurs when the angle is zero.
// Not a problem: just set an arbitrary normalized axis.
result.Xyz = SCNVector3.UnitX;
}
return(result);
}
/// <summary>
/// Convert the current quaternion to axis angle representation
/// </summary>
/// <param name="axis">The resultant axis</param>
/// <param name="angle">The resultant angle</param>
public void ToAxisAngle(out SCNVector3 axis, out pfloat angle)
{
SCNVector4 result = ToAxisAngle();
axis = result.Xyz;
angle = result.W;
}
/// <summary>Transform a Vector by the given Matrix</summary>
/// <param name="vec">The vector to transform</param>
/// <param name="mat">The desired transformation</param>
/// <returns>The transformed vector</returns>
public static SCNVector4 Transform(SCNVector3 vec, SCNMatrix4 mat)
{
SCNVector4 v4 = new SCNVector4(vec.X, vec.Y, vec.Z, 1.0f);
SCNVector4 result;
result.X = SCNVector4.Dot(v4, mat.Column0);
result.Y = SCNVector4.Dot(v4, mat.Column1);
result.Z = SCNVector4.Dot(v4, mat.Column2);
result.W = SCNVector4.Dot(v4, mat.Column3);
return(result);
}
/// <summary>Transform a SCNVector3 by the given Matrix, and project the resulting Vector4 back to a SCNVector3</summary>
/// <param name="vec">The vector to transform</param>
/// <param name="mat">The desired transformation</param>
/// <returns>The transformed vector</returns>
public static SCNVector3 TransformPerspective(SCNVector3 vec, SCNMatrix4 mat)
{
SCNVector4 h = Transform(vec, mat);
return(new SCNVector3(h.X / h.W, h.Y / h.W, h.Z / h.W));
}
/// <summary>Transform a Vector by the given Matrix</summary>
/// <param name="vec">The vector to transform</param>
/// <param name="mat">The desired transformation</param>
/// <param name="result">The transformed vector</param>
public static void Transform(ref SCNVector3 vec, ref SCNMatrix4 mat, out SCNVector4 result)
{
SCNVector4 v4 = new SCNVector4(vec.X, vec.Y, vec.Z, 1.0f);
SCNVector4.Transform(ref v4, ref mat, out result);
}
/// <summary>
/// Constructs a new Vector3 from the given Vector4.
/// </summary>
/// <param name="v">The Vector4 to copy components from.</param>
public SCNVector3(SCNVector4 v)
{
X = v.X;
Y = v.Y;
Z = v.Z;
}
