This is exactly what I would like to know, i.e. how to add 2D image/texture when a frame marker is recognised. I have asked this question here: https://developer.vuforia.com/forum/ios/dynamic-image-not-rendered-correctly-ipad

The problem I'm facing is that if I add a 3D Plane game object in Unity Editor at design time my image is rendered correctly when deployed to iPad. If I add 3D Plane game object programmatically at run-time, then when deployed to iPad it is rendered as pink/magenta rectangle. Of course it works in Unity Player.

My question what is the difference between Plane and Quad? Would it make any difference to my problem?

OK, that is pretty easy to do:

first, you need to render a "quad" instead of the classic "teapot"; the texture of your picture is applied on the quad; you can find the full code to render a textured quad in the VideoPlayback sample for instance (see the quadVertices, quadNormals, quadTexCoords variables and how they are used in the OpenGL code)

second, you will need to adjust the pose matrix so that it behaves like a Billboard, i.e. by resetting (clearing) the rotational part of the matrix and only keeping the translational one; in practice this can be done with this simple code:

QCAR::Matrix44F modelViewMatrix =
            QCAR::Tool::convertPose2GLMatrix(result->getPose());

        // reset the rotational part of the pose matrix
        modelViewMatrix.data[0] = 1.0f;
        modelViewMatrix.data[1] = 0.0f;
        modelViewMatrix.data[2] = 0.0f;
        modelViewMatrix.data[3] = 0.0f;
        modelViewMatrix.data[4] = 0.0f;
        modelViewMatrix.data[5] = 1.0f;
        modelViewMatrix.data[6] = 0.0f;
        modelViewMatrix.data[7] = 0.0f;
        modelViewMatrix.data[8] = 0.0f;
        modelViewMatrix.data[9] = 0.0f;
        modelViewMatrix.data[10] = 1.0f;
        modelViewMatrix.data[11] = 0.0f;

This should do the trick.

2D picture move with the marker. How can I do that

OK. Just for confirmation: should the 2D picture move with the marker, or do you want to just show it statically in the center of the screen when the marker is detected?

I mean "screen-aligned", showing the 2D picture instead of 3D model.

Hi, do you want to render the 2D picture as a billboard (i.e. a "screen-aligned" object, positioned in 3D on your marker, but aligned with the screen) or as a 3D surface aligned with the Marker plane ?