I'm trying to create a WPF application using the MVVM pattern.
In my view (UserControl class derived) I've placed the HelixViewport3D control and I've assigned an instance of my ViewModel to the DataContext property

<h:HelixViewport3D RotateGesture="Alt+RightClick" PanGesture="RightClick">
<h:HelixViewport3D.Camera>
<OrthographicCamera Position="80.22,0,0" LookDirection="-80.22,0,0" UpDirection="0,0,1" Width="56"/>
</h:HelixViewport3D.Camera>
<h:SunLight />
<ModelVisual3D Content="{Binding Model3D}" />
</h:HelixViewport3D>

The ModelVisual3D content property is binded with the Model3D propery of my ViewModel.

All works fine but I would like to create the model in a function that works in background. I've tried to do this using both the BackgroundWorker class that the Task.Factory.StartNew but I've always get the message that the object is property of another thread.

One of my attempt is the following

public class MyViewModel : BaseViewModel
{

private MyData _model; // the data on which to generate my 3d model
private Model3DGroup _model3d;
private CancellationTokenSource _source;

public Model3DGroup Model3D
{
    get { return _model3d; }
    set
    {
        if (_model3d != value)
        {
            _model3d = value;
             RaisePropertyChanged(() => Model3D);
        }
    }
}

private void CreateModel3D(object dispatcherObject)
{
    Dispatcher dispatcher = (Dispatcher)dispatcherObject;

    Material nodesMaterial = MaterialHelper.CreateMaterial(Colors.Green);
    double size = Math.Max(_model.Limits.Width, _model.Limits.Height);
    double dn = size / 100;
    double db = size / 120;
    int thetaDiv = 10;

    foreach (Strauss.Node node in _model.Nodes)
    {
         MeshBuilder meshBuilder = new MeshBuilder(false, false);
         meshBuilder.AddSphere(new Point3D(node.X, node.Y, node.Z), dn, thetaDiv, thetaDiv / 2);
         MeshGeometry3D mesh = meshBuilder.ToMesh(true);
         dispatcher.Invoke((Action)(() => _model3d.Children.Add(new GeometryModel3D { Geometry = mesh, Material = nodesMaterial, BackMaterial = nodesMaterial })));
    }
}

private void ModelLoaded(object sender, EventArgs args)
{
    System.Windows.Window win = App.Current.Windows[0];
    DocManagerViewModel docManager = win.DataContext as DocManagerViewModel;
    _source = new CancellationTokenSource();
    Task task = Task.Factory.StartNew(CreateModel3D, _model3d.Dispatcher, _source.Token);
}

}

The process starts from the ModelLoaded event handler.

Can anyone please help me?
Thanks in advance.

1 -- Use Task.Factory.StartNew(). BackgroundWorker is prone to a race condition.
2 -- All WPF objects, including GeometryModel3D and MeshGeometry3D, have to be "Frozen" to be passed between threads. See "Freezable" in the MSDN documentation.

Change the code in CreateModel3D from what you have to something like:

var gm3d = new GeometryModel3D { Geometry = mesh, Material = nodesMaterial, BackMaterial = nodesMaterial };
dispatcher.Invoke((Action)(() => _model3d.Children.Add(gm3d.GetAsFrozen())));

Experts,

I have the back end down. Right now, the XAML is the pain.

Given the following working XAML, how should I implement the backend collection of "Conns" (Connections, or Flights) in the Current Flight Demo code (which this came from)?

Below in the abbreviated XAML, this section toward the bottom is the one in question:

   <ItemsControl ItemsSource="{Binding Conns}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                    <Viewport3D /> <--- ??? or...?
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
    </ItemsControl>

I'm 100% on the backend. I just can't figure out how to make the XAML under Helix3D ready to bind to/show the collection...

Any help at all REALLY appreciated!!!

pat
:)

<Window x:Class="TheEarthWindow"
    x:Name="TheGlobe"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:t="clr-namespace:HelixToolkit.Wpf;assembly=HelixToolkit.Wpf" 
    Title="TheEarthWindow" Height="800" Width="800">
    <Grid>
        <Grid.Resources>
        [...]
        </Grid.Resources>
        <Grid.Triggers>
        [...]
        </Grid.Triggers>
        <t:HelixViewport3D x:Name="view1" 
                           Background="Black" 
                           CameraRotationMode="Turnball"
                           ClipToBounds="False"
                           Grid.Column="0" 
                           IsHeadLightEnabled="True" 
                           IsHitTestVisible="True"
                           IsPanEnabled="False"
                           IsZoomEnabled="True"
                           MouseDown="OnMouseDown" 
                           MouseMove="OnMouseMove" 
                           ShowCameraInfo="False"
                           ShowCameraTarget="False"
                           ShowCoordinateSystem="False"
                           ShowFieldOfView="False"
                           ShowFrameRate="True"
                           ShowTriangleCountInfo="False"
                           ShowViewCube="True"
                           SubTitle="vASA Global Monitor"
                           SubTitleSize="40"
                           Title="vASA"
                           ZoomExtentsWhenLoaded="True" >
            <t:HelixViewport3D.Camera>
                <PerspectiveCamera Position="600,27400,0" 
                                   LookDirection="0,1,0" 
                                   UpDirection="0,0,1" 
                                   NearPlaneDistance="0.01" 
                                   FarPlaneDistance="Infinity" 
                                   FieldOfView="40">
                    <PerspectiveCamera.Transform>
                    <Transform3DGroup>
                        <RotateTransform3D>
                            <RotateTransform3D.Rotation>
                                <AxisAngleRotation3D Axis="0,0,1" Angle="0" x:Name="camRotation" />
                            </RotateTransform3D.Rotation>
                        </RotateTransform3D>
                    </Transform3DGroup>
                    </PerspectiveCamera.Transform>
                </PerspectiveCamera>
            </t:HelixViewport3D.Camera>
            <t:SunLight />
            <t:SphereVisual3D x:Name="TheEarthSphere" 
                              Material="{StaticResource EarthJPG}"
                              Radius="1" 
                              ThetaDiv="25" 
                              PhiDiv="25" >
<!-- WHAT GOES HERE FOR TUBES? -->
        <ItemsControl ItemsSource="{Binding Conns}">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                        <Viewport3D /> <--- ??? or...?
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
        </ItemsControl>
<!-- IS THE ABOVE EVEN IN THE RIGHT PART OF THE TREE? -->
            </t:SphereVisual3D>
        </t:HelixViewport3D>
    </Grid>
</Window>

I need to perform an operation right after the user has stopped moving the camera (everytime he does it).

I'm doing it now by subscribing to every MouseEvent that allows interaction with the camera (specifically ButtonUp). The problem is that when the user has zoomed I don't have a way to know when he has stopped zooming. Other issue of capturing mouse events is that when the camera change has been generated programatically (set some saved view, etc) and there is some animation I can't do it either.

I would like to know if there is some event that I can subscribe to know when the Camera is "done", when it has stopped moving.

If such event doesn't exist I would like to know if it is possible to create one without modifying the source code of HelixToolKit and how it could be done.

Thank you very much.