C# WPF实现动态3D光照效果

<Viewport3D Name="mainViewport">
    <Viewport3D.Camera>
        <PerspectiveCamera x:Name="camera"/>
    </Viewport3D.Camera>
    <ModelVisual3D x:Name="visual3d">
        <ModelVisual3D.Content>
            <Model3DGroup x:Name="MainGroup">
                <AmbientLight Color="White"/>
            </Model3DGroup>
        </ModelVisual3D.Content>
    </ModelVisual3D>
</Viewport3D>

private void initialize3D()
{
    DefineCamera(mainViewport);
    DefineModel(MainGroup);
}

private void DefineCamera(Viewport3D viewport)
{
    camera = new PerspectiveCamera();
    camera.FieldOfView = 60;
    new Ctrl(camera, viewport, this, viewport, viewport);
}
MeshGeometry3D mesh;
private void DefineModel(Model3DGroup group)
{
    // 生成曲面.
    mesh = SetEarth(50, 50);
    ImageBrush smileyBrush = new ImageBrush();
    smileyBrush.ImageSource = new BitmapImage(new Uri("cs3d_8.jpg", UriKind.Relative));
    SurfaceModel = new GeometryModel3D(mesh, new DiffuseMaterial(smileyBrush));
    group.Children.Add(SurfaceModel);
}

<DockPanel LastChildFill="True">
<WrapPanel DockPanel.Dock="Top">
    <WrapPanel DockPanel.Dock="Top" Margin="0 0 10 0">
        <WrapPanel>
            <TextBlock Text="Inner"/>
            <Slider Width="200" Value="3" Maximum="20" Minimum="1" x:Name="sInner"/>
            <TextBox Text="{Binding ElementName=sInner,Path=Value, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" 
         Margin="0 5" Width="30"/>
        </WrapPanel>
        <WrapPanel Margin="10 0 0 0">
            <TextBlock Text="Outer"/>
            <Slider Width="200" Value="10" Maximum="30" Minimum="1" x:Name="sOuter"/>
            <TextBox Text="{Binding ElementName=sOuter,Path=Value, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" 
         Margin="0 5" Width="30"/>
        </WrapPanel>
    </WrapPanel>
    <Viewport3D Name="mainViewport">
            </Viewport3D>
</DockPanel>

<WrapPanel Margin="5">
    <TextBlock Text="R"/>
    <Slider Width="200" Value="150" Maximum="255" Minimum="0" x:Name="sColorR" ValueChanged="colorChanged"/>
    <TextBox Text="{Binding ElementName=sColorR,Path=Value, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" 
     Margin="0 5" Width="30"/>
</WrapPanel>

private void colorChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
    if (!isInit)
        return;
    mySpotLight.Color = Color.FromRgb(
        (byte)sColorR.Value, (byte)sColorG.Value, (byte)sColorB.Value);
}