Helix 3D Toolkit - ZoomExtents method call works different than activating ZoomExtents through gesture

Question

I've been working on a small 3D preview window in a MVVM style application... The view is created then its data context is set. Therefore it seems that ZoomExtentsWhenLoaded="True" doesn't seem to help do what I need. I need something like, ZoomExtentsWhenDataContextChanges.

Interestingly, I've found that if I use a mouse gesture like the one defined below, I can physically click on the HelixViewport3D and it will perform a ZoomExtents.

HelixViewport3D.ZoomExtentsGesture = new MouseGesture(MouseAction.LeftDoubleClick);

However, if do something like this...

HelixViewport3D.DataContextChanged += (o, e) => ResetCamera();

private void ResetCamera()
{
    var dc = HelixViewport3D.DataContext as WellSurveyPlot3DViewModel;
    HelixViewport3D.ResetCamera();
    HelixViewport3D.Camera = dc.PerspectiveCamera;
    HelixViewport3D.ZoomExtents();
}

The viewport does zoom, it just doesn't center itself, like it does when activating ZoomExtents when using the mouse gesture.

I tried ResetCamera, and several other things... What is the standard way of dealing with keeping a viewport around and swapping out the DataContext instead of creating a new one each time?

Answer 1

I fixed this with an attached property. I read through the HelixViewport3D source code and got this idea, after noticing how the camera works. It seems an update to the default camera through a property binding doesn't really do anything after the control is initialized.

  public static class HelixViewport3DZoomExtent
{
    private static readonly Type OwnerType = typeof(HelixViewport3DZoomExtent);
    public static readonly DependencyProperty ZoomExtentsOnUpdateProperty = DependencyProperty.RegisterAttached("ZoomExtentsOnUpdate", typeof(bool), OwnerType, new PropertyMetadata(false, OnDataContextChanged));

    public static bool GetZoomExtentsOnUpdate(DependencyObject obj)
    {
        return (bool)obj.GetValue(ZoomExtentsOnUpdateProperty);
    }
    public static void SetZoomExtentsOnUpdate(DependencyObject obj, bool value)
    {
        obj.SetValue(ZoomExtentsOnUpdateProperty, value);
    }
    private static void OnDataContextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var viewport = d as HelixViewport3D;
        if (viewport == null) return;
        if (viewport.DataContext == null) return;
        viewport.Camera = viewport.DefaultCamera;
        viewport.ZoomExtents();
    }
}

Here is the Xaml

 <Border BorderBrush="Black" BorderThickness="1">

    <Grid>

        <h:HelixViewport3D Name="HelixViewport3D" 
                           PanGesture="LeftClick"
                           DataContext="{Binding PreviewPlot, UpdateSourceTrigger=PropertyChanged}"
                           DefaultCamera="{Binding PerspectiveCamera, UpdateSourceTrigger=PropertyChanged}" 
                           services:HelixViewport3DZoomExtent.ZoomExtentsOnUpdate="{Binding RelativeSource={RelativeSource AncestorType={x:Type views:WellSurveyPlot3DPreview}}, 
                                                                                    Path=DataContext.PreviewUpdatedReZoom, UpdateSourceTrigger=PropertyChanged}">

            <h:SunLight/>

            <h:TubeVisual3D  Path="{Binding TubePath}" Diameter="75" ThetaDiv="12" IsPathClosed="False" Fill="LightGray"/>

            <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength}" MajorDistance="{Binding MajorGridLines}" Thickness="25"
                             MinorDistance="{Binding MajorGridLines, UpdateSourceTrigger=PropertyChanged}" LengthDirection="1,0,0" Normal="0,0,1" 
                             Center="{Binding BottomPlaneCenter,UpdateSourceTrigger=PropertyChanged}" Fill="Red"   />
            <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength, UpdateSourceTrigger=PropertyChanged}" LengthDirection="0,0,1" Normal="1,0,0"  Thickness="25"
                             MajorDistance="{Binding MajorGridLines}" MinorDistance="{Binding MajorGridLines}"
                             Center="{Binding BackLeftPlaneCenter, UpdateSourceTrigger=PropertyChanged}" Fill="Blue" />
            <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength, UpdateSourceTrigger=PropertyChanged}" LengthDirection="1,0,0" Normal="0,1,0" Thickness="25"
                             MajorDistance="{Binding MajorGridLines}" MinorDistance="{Binding MajorGridLines}" 
                             Center="{Binding BackRightPlaneCenter,UpdateSourceTrigger=PropertyChanged}" Fill="Green" />

        </h:HelixViewport3D>

        <Button Content="Open Well Viewer" HorizontalAlignment="Left"  VerticalAlignment="Top" Command="{Binding OpenWindowCmd}"/>

    </Grid>
</Border>

In my view model I have to toggle my PreviewUpdateReZoom property.

private void LoadSurveyPoints(List<WellSurveyPointCalculated> surveyPoints)
    {
        _coordinatesCalculator = _calcGlobalCoordsFactory.Create(surveyPoints);
        _wellXyzCoordinates = _coordinatesCalculator.PlotGlobalCoordinates(100).ToList();
        PreviewPlot = WellSurveyPlot3DViewModel();
        PreviewUpdatedReZoom = false;//Toggle true false to send property changed and get attached property to fire.
        PreviewUpdatedReZoom = true;
    }

This now works such that every new item drawn into the viewport has the correct camera settings and zooms to extents...