How do I calculate WPF all camera setting dynamically in the code?

Question

I have Viewport3D in the Window. it will change the size when the window size changed.

<Window>
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="100"/>
      <RowDefinition/>
    <Grid.RowDefinitions>
    <Label Grid.Row="0" Content="top label"/>
    <Viewport3D Grid.Row="1" x:Name="vp3D" >
            <Viewport3D.Camera >
                 <PerspectiveCamera x:Name="pCamera"  LookDirection="0 0 -1" UpDirection="0 1 0" />
            </Viewport3D.Camera>
            <Viewport2DVisual3D x:Name="v2dv3d">
                  <Viewport2DVisual3D.Geometry>
                      <MeshGeometry3D x:Name="mg3d" TextureCoordinates="0,0 0,1 1,1 1,0" TriangleIndices="0 1 2 0 2 3"/>
                   </Viewport2DVisual3D.Geometry>
                   <Viewport2DVisual3D.Material>
                         <DiffuseMaterial Viewport2DVisual3D.IsVisualHostMaterial="True" Brush="White"/>
                   </Viewport2DVisual3D.Material>

                          <Image  Height="{Binding ElementName=vp3D, Path=ActualHeight}" Width="{Binding ElementName=vp3D, Path=ActualWidth}" Stretch="Fill"/>

            </Viewport2DVisual3D>
            <ModelVisual3D>
                 <ModelVisual3D.Content>
                      <DirectionalLight Color="#FFFFFFFF" Direction="0,0,-1"/>
                 </ModelVisual3D.Content>
           </ModelVisual3D>
  </Viewport3D>
 </Grid>
</Window

Now I want the image show on like it's the original 2d window(look like nothing changed, but actually the image is 3d).

But problem is If I want it looking same as the same as WPF original look at, I must change some Camera settings, like PerspectiveCamera.Position or MeshGeometry3D.Position. because the Viewport3D will change the size dynamically when the window change size, I must dynamically calculate the Viewport3D settings. Is there anyway to do ?

I've already tried this, but can't calculate correctly: WPF 3D: Fitting entire image to view with PerspectiveCamera

Answer 1

I'm not sure if that is what you want, but have you tried this?

<Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="100"/>
      <RowDefinition/>
    </Grid.RowDefinitions>
    <Label Grid.Row="0" Content="top label"/>
    <Image HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Row="1" Stretch="Fill"/>
    <Viewport3D Grid.Row="1" x:Name="vp3D">
            <Viewport3D.Camera >
                 <PerspectiveCamera x:Name="pCamera" Position="0,0,1" LookDirection="0,0,-1" />
            </Viewport3D.Camera>
            <Viewport2DVisual3D x:Name="v2dv3d">
                  <Viewport2DVisual3D.Geometry>
                      <MeshGeometry3D x:Name="mg3d" Positions="-1,1,0 -1,-1,0 1,-1,0 1,1,0" TextureCoordinates="0,0 0,1 1,1 1,0" TriangleIndices="0 1 2 0 2 3"/>
                   </Viewport2DVisual3D.Geometry>
                   <Viewport2DVisual3D.Material>
                         <DiffuseMaterial Viewport2DVisual3D.IsVisualHostMaterial="True" Brush="White"/>
                   </Viewport2DVisual3D.Material>
            </Viewport2DVisual3D>
            <ModelVisual3D>
                 <ModelVisual3D.Content>
                      <DirectionalLight Color="#FFFFFFFF" Direction="0,0,-1"/>
                 </ModelVisual3D.Content>
           </ModelVisual3D>
      </Viewport3D>
</Grid>

Answer 2

I finish it by myself.

// get the Viewport3D size first, If you want to use .ActualWidth or .ActualHeight property get it, make sure your application loaded finish, otherwise it will return 0.
double height = ; // get the Viewport3D height or calculate the height first
double width = ; //  get the Viewport3D width or calculate the width first


mg3d.Positions.Clear();
mg3d.Positions.Add(new Point3D(-width, height, 0.0));
mg3d.Positions.Add(new Point3D(-width, -height, 0.0));
mg3d.Positions.Add(new Point3D(width, -height, 0.0));
mg3d.Positions.Add(new Point3D(width, height, 0.0));


double fieldOfViewInRadians = pCamera.FieldOfView * (Math.PI / 180.0);
var z = (width) / Math.Tan(0.5 * fieldOfViewInRadians);
pCamera.Position = new Point3D(0.0, 0.0, z);

You also need to make sure calculate it again if your window size changed. After that, you could do any 3d animation which you want.