public static void CreateBillboard(ref FVector3 objectPosition, ref FVector3 cameraPosition,
ref FVector3 cameraUpVector, FVector3?cameraForwardVector, out FMatrix result)
{
FVector3 translation = objectPosition - cameraPosition;
FVector3 backwards, right, up;
FVector3.Normalize(ref translation, out backwards);
FVector3.Normalize(ref cameraUpVector, out up);
FVector3.Cross(ref backwards, ref up, out right);
FVector3.Cross(ref backwards, ref right, out up);
result = Identity;
result.Backward = backwards;
result.Right = right;
result.Up = up;
result.Translation = translation;
}
public static void CreateWorld(ref FVector3 position, ref FVector3 forward, ref FVector3 up, out FMatrix result)
{
FVector3 x, y, z;
FVector3.Normalize(ref forward, out z);
FVector3.Cross(ref forward, ref up, out x);
FVector3.Cross(ref x, ref forward, out y);
x.Normalize();
y.Normalize();
result = new FMatrix();
result.Right = x;
result.Up = y;
result.Forward = z;
result.Translation = position;
result.M44 = 1f;
}
public static void CreateLookAt(ref FVector3 cameraPosition, ref FVector3 cameraTarget, ref FVector3 cameraUpVector,
out FMatrix result)
{
// http://msdn.microsoft.com/en-us/library/bb205343(v=VS.85).aspx
FVector3 vz = FVector3.Normalize(cameraPosition - cameraTarget);
FVector3 vx = FVector3.Normalize(FVector3.Cross(cameraUpVector, vz));
FVector3 vy = FVector3.Cross(vz, vx);
result = Identity;
result.M11 = vx.X;
result.M12 = vy.X;
result.M13 = vz.X;
result.M21 = vx.Y;
result.M22 = vy.Y;
result.M23 = vz.Y;
result.M31 = vx.Z;
result.M32 = vy.Z;
result.M33 = vz.Z;
result.M41 = -FVector3.Dot(vx, cameraPosition);
result.M42 = -FVector3.Dot(vy, cameraPosition);
result.M43 = -FVector3.Dot(vz, cameraPosition);
}