[solved] Vector2.Transform(Vector2, Matrix) returns {X:n. def. Y:n. def.}

Graphics
1

I’m trying to convert a Vector2 screen position to a world position. I’ve found this nice method in a question on stackoverflow:

public Vector2 ScreenToWorld(Vector2 onScreen)
{
    var matrix = Matrix.Invert(World.Camera.CurrentTransformation);
    return Vector2.Transform(onScreen, matrix);
}

But when I use this with the Matrix of my camera it only returns this:

{X:n. def. Y:n. def.} // Output of Vector2.ToString()

My Matrix is build like this:

m_transform = Matrix.CreateTranslation(new Vector3(-m_position.X, -m_position.Y, 0f)) *
    Matrix.CreateScale(new Vector3(m_zoom, m_zoom, 0)) *
    Matrix.CreateTranslation(new Vector3(m_viewport.Width / 2f, m_viewport.Height / 2f, 0));

When I try to compare the result with other Vector2 positions it allways return true. For Example, I have a clickable object, and even if I click outside of the object it returns that it is being clicked.

2

Had a look into how Vector2.Transform() works.

return new Vector2((point.X * matrix.M11) + (point.Y * matrix.M21) + matrix.M41, (point.X * matrix.M12) + (point.Y * matrix.M22) + matrix.M42);

And I also had a look into my Matrix and checked the used values.

// M11: 0.325, M12: 0, M21: 0, M22: 0.325, M41: 110.5, M42 279.5

But theese are the values for the actual Matrix, right? So I do Matrix.Invert() and look them up again…

// M11: {n. def.}, M12: {n. def.}, M21: {n. def.}, M22: {n. def.}, M41: {n. def.}, M42 {n. def.}

It’s way past bed time here. I will take a look into how Matrix.Invert() works tomorrow. Just wanted to leave this as an update.
I don’t really think all this will lead me to a solution, so pleeease for god’s sake help me :smile:

3

Maybe scale should have been (m_zoom, m_zoom, 1)? I don’t know.

If you are just starting with this kind of math you’d better stick to the standard methods to create a View and projection matrix (Matrix.CreateLookAt(), Matrix.CreateOrthographic()),
and the stock methods to convert from and to screen space (Viewport.Project() and Viewport.Unproject())

4

Thing is, when you are just starting with this kinda stuff, you have no damn clue what those standard methods are. Or how they are used. :stuck_out_tongue: thx for your tip tho :smiley:

Maybe scale should have been (m_zoom, m_zoom, 1)? I don’t know.

oh you doo :smiley: because that is the solution to my problem. Thank you sir! :smiley:

1 Like
5

Method’s name say it all :wink:

6

Just a lucky guess. :slight_smile: