public float Determinant()
{
//Current implementation of cross far from optimal without shuffles. This assumes it'll eventually be accelerated.
Vector3 cross;
Vector3x.Cross(ref Y, ref Z, out cross);
return(Vector3.Dot(X, cross));
}
public static void Invert(ref Matrix3x3 m, out Matrix3x3 inverse)
{
//Current implementation of cross far from optimal without shuffles, and even then this has some room for improvement.
//Inverts should be really rare, so it's not too concerning. Use the scalar version when possible until ryujit improves (and we improve this implementation).
Vector3 yz, zx, xy;
Vector3x.Cross(ref m.Y, ref m.Z, out yz);
Vector3x.Cross(ref m.Z, ref m.X, out zx);
Vector3x.Cross(ref m.X, ref m.Y, out xy);
var inverseDeterminant = 1f / Vector3.Dot(m.X, yz);
inverse.X = yz * inverseDeterminant;
inverse.Y = zx * inverseDeterminant;
inverse.Z = xy * inverseDeterminant;
Transpose(ref inverse, out inverse);
}
/// <summary>
/// Creates a view matrix pointing in a direction with a given up vector.
/// </summary>
/// <param name="position">Position of the camera.</param>
/// <param name="forward">Forward direction of the camera.</param>
/// <param name="upVector">Up vector of the camera.</param>
/// <param name="viewMatrix">Look at matrix.</param>
public static void CreateView(ref Vector3 position, ref Vector3 forward, ref Vector3 upVector, out Matrix viewMatrix)
{
float length = forward.Length();
var z = forward / -length;
Vector3 x;
Vector3x.Cross(ref upVector, ref z, out x);
x = Vector3.Normalize(x);
Vector3 y;
Vector3x.Cross(ref z, ref x, out y);
viewMatrix.X = new Vector4(x.X, y.X, z.X, 0);
viewMatrix.Y = new Vector4(x.Y, y.Y, z.Y, 0);
viewMatrix.Z = new Vector4(x.Z, y.Z, z.Z, 0);
viewMatrix.W = new Vector4(
-Vector3.Dot(x, position),
-Vector3.Dot(y, position),
-Vector3.Dot(z, position), 1);
}
