How to HitTest XAML 3D object in WPF

Question

What I want to do is to know if the user click the red button of my joystick. (for the purpose, I draw over the real joystick graphic to keep our drawing private)

This joystick is a XAML 3D.

The red button is a GeometryModel3D object, with the x:Name "Geo_Btn_CSS_TAKE". When I click on the joystick, I can do a HitTest, he gives me all the GeometryModel3D object but I can't access to the x:Name, so I cannot know witch one is the good one...

And this is how I do my HitTest:

private void OnTouchMouseDown(EventArgs e)
{
    Viewport3D viewport3D = WtoHitTest((Grid)Parent, e) as Viewport3D; // My own HitTest works well, I get my viewport3D

    Point mouseposition = WtoHelper.GetPositionFromEvent(e, viewport3D); // Get the point if it's a mouse event or touch event
    Point3D testpoint3D = new Point3D(mouseposition.X, mouseposition.Y, 0);
    Vector3D testdirection = new Vector3D(mouseposition.X, mouseposition.Y, 10);
    PointHitTestParameters pointparams = new PointHitTestParameters(mouseposition);
    RayHitTestParameters rayparams = new RayHitTestParameters(testpoint3D, testdirection);

    VisualTreeHelper.HitTest(viewport3D, null, HTResult, pointparams);
}

public HitTestResultBehavior HTResult(System.Windows.Media.HitTestResult rawresult)
{
    RayHitTestResult rayResult = rawresult as RayHitTestResult;

    if (rayResult != null)
    {
        RayMeshGeometry3DHitTestResult rayMeshResult = rayResult as RayMeshGeometry3DHitTestResult;

        if (rayMeshResult != null)
        {
            GeometryModel3D hitgeo = rayMeshResult.ModelHit as GeometryModel3D;

            **// HERE I NEED TO KNOW WHAT IS MY GEOMETRYMODEL3D'S X:NAME**
            // ANY IDEA???
        }
    }
    return HitTestResultBehavior.Continue;
}

What else I know:

• My 3D object does not have a position (x,y) that I can bind to
• I cannot insert non-3D element in the Viewport3D
• I cannot access to the x:Name of a 3D object
• 3D object or not FrameworkElement or Visual. They are Media3D

The way I did it, I only need to know the x:name to complete my implementation... if someone have a tips or an other way to go, let me know.

Thank you

EDIT: this is the properties of my 3D object:

Answer 1

I know this is an old post, but it is high in the search rankings and I stumbled upon it because I am learning WPF 3D. A second way to solve the problem is to use the Helix Toolkit. They extend GeometryModel3D with the methods SetName() and GetName(). So you can call it something, and then when doing the ray test you can get the name:

RayMeshGeometry3DHitTestResult rayHit = hr as RayMeshGeometry3DHitTestResult; //hr is of type HitTestResult
MessageBox.Show("Model found: " + rayHit.ModelHit.GetName());

Of course this means adding Helix Toolkit into the mix, but so far it has been worth it in several ways.

Answer 2

The one thing that I can think of that will work and is XAML friendly is to define your own attached property on GeometryModel3D. Look here for how to create custom attached properties.