/// <summary>
/// Build a world space to camera space matrix
/// </summary>
/// <param name="eye">Eye (camera) position in world space</param>
/// <param name="target">Target position in world space</param>
/// <param name="up">Up vector in world space (should not be parallel to the camera direction, that is target - eye)</param>
/// <returns>A SCNMatrix4 that transforms world space to camera space</returns>
public static SCNMatrix4 LookAt(SCNVector3 eye, SCNVector3 target, SCNVector3 up)
{
SCNVector3 z = SCNVector3.Normalize(eye - target);
SCNVector3 x = SCNVector3.Normalize(SCNVector3.Cross(up, z));
SCNVector3 y = SCNVector3.Normalize(SCNVector3.Cross(z, x));
SCNMatrix4 rot = new SCNMatrix4(new SCNVector4(x.X, y.X, z.X, 0.0f),
new SCNVector4(x.Y, y.Y, z.Y, 0.0f),
new SCNVector4(x.Z, y.Z, z.Z, 0.0f),
SCNVector4.UnitW);
SCNMatrix4 trans = SCNMatrix4.CreateTranslation(-eye);
return(trans * rot);
}
public static void Multiply(ref SCNQuaternion left, ref SCNQuaternion right, out SCNQuaternion result)
{
result = new SCNQuaternion(
right.W * left.Xyz + left.W * right.Xyz + SCNVector3.Cross(left.Xyz, right.Xyz),
left.W * right.W - SCNVector3.Dot(left.Xyz, right.Xyz));
}
public static SCNQuaternion Mult(SCNQuaternion left, SCNQuaternion right)
{
return(new SCNQuaternion(
right.W * left.Xyz + left.W * right.Xyz + SCNVector3.Cross(left.Xyz, right.Xyz),
left.W * right.W - SCNVector3.Dot(left.Xyz, right.Xyz)));
}