Question

I am trying to emulate Vector3.TransformNormal without the DirectX library.

Is anyone able to explain how this function works, to allow me to recreate the function?

So far I know the inputs and have seen the description of what it does, but I don’t know the calculations.

public static Vector3 TransformNormal(
    Vector3 source,
    Matrix sourceMatrix
)

Answer 1

This should do it (didn’t test)

public Vector3 TransformNormal(Vector3 normal, Matrix matrix)
{    
    return new Vector3
    {
        X = normal.X * matrix.M11 + normal.Y * matrix.M21 + normal.Z * matrix.M31,
        Y = normal.X * matrix.M12 + normal.Y * matrix.M22 + normal.Z * matrix.M32,
        Z = normal.X * matrix.M13 + normal.Y * matrix.M23 + normal.Z * matrix.M33
    };
}