Light Effect

Light Effect shows how you can use PointLight with an element to create a Light Effect in an application using the Windows App SDK.

Step 1

Follow Setup and Start on how to get Setup and Install what you need for Visual Studio 2022 and Windows App SDK.

Step 2

Then in Visual Studio within Solution Explorer for the Solution, right click on the Project shown below the Solution and then select Add then New Item…

Step 3

Then in Add New Item from the C# Items list, select Code and then select Code File from the list next to this, then type in the name of Library.cs and then Click on Add.

Step 4

You will now be in the View for the Code of Library.cs, within this type the following Code:

using Microsoft.UI;
using Microsoft.UI.Composition;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Hosting;
using System;

internal class Library
{
    private PointLight _light;

    public void SetLight(FrameworkElement element)
    {
        var visual = ElementCompositionPreview.GetElementVisual(element);
        var compositor = visual.Compositor;
        _light = compositor.CreatePointLight();
        _light.Color = Colors.White;
        _light.CoordinateSpace = visual;
        _light.Targets.Add(visual);
        _light.Offset = new System.Numerics.Vector3(
            -(float)element.ActualWidth * 2,
            (float)element.ActualHeight / 2,
            (float)element.ActualHeight);
        var animation = compositor.CreateScalarKeyFrameAnimation();
        animation.IterationBehavior = AnimationIterationBehavior.Forever;
        animation.InsertKeyFrame(1, 2 * (float)element.ActualWidth);
        animation.Duration = TimeSpan.FromSeconds(5.0f);
        _light.StartAnimation("Offset.X", animation);
    }

    public void ClearLight()
    {
        if (_light != null)
            _light.Targets.RemoveAll();
    }
}                                                                                                                                                             
                                    

The Class that has been defined in Library.cs has a Member for a PointLight then there is a Method of SetLight which will create a Light Effect for a FrameworkElement by first creating an Element Visual with ElementCompositionPreview you'll also notice the use of var, which means the type of the value doesn't need to be explicitly specified, instead it will be Inferred. Then a Compositor is obtained from this a PointLight is configured where various values are set to display it as needed. There is also an Animation used which will make the PointLight move across the FrameworkElement with the specified Behaviour. The other Method of ClearLight is used to remove the Light Effect of the PointLight.

Step 5

Step 6

In the XAML for MainWindow.xaml there will be some XAML for a StackPanel, this should be Removed:

<StackPanel Orientation="Horizontal" 
HorizontalAlignment="Center" VerticalAlignment="Center">
    <Button x:Name="myButton" Click="myButton_Click">Click Me</Button>
</StackPanel>                               
                                    

Step 7

While still in the XAML for MainWindow.xaml above </Window>, type in the following XAML:

<Grid>
    <Viewbox Margin="25">
        <Rectangle Name="Display" Height="400" Width="400" 
        Margin="50" Stretch="Uniform" Fill="#FF5c2d91"/>
    </Viewbox>
    <CommandBar VerticalAlignment="Bottom" HorizontalAlignment="Stretch" >
        <AppBarButton Icon="Accept" Label="Accept" Click="Accept_Click"/>
        <AppBarButton Icon="Cancel" Label="Clear" Click="Clear_Click"/>
    </CommandBar>
</Grid>                                                                                                                                      
                                    

This XAML features a Grid with a ViewBox which is used to Scale elements, then within this is a which is the FrameworkElement that will have the Light Effect applied to it. Then there is a CommandBar with an AppBarButton to apply the Light Effect of Accept and another to remove it of Clear.

Step 8

Step 9

In the Code for MainWindow.xaml.cs there be a Method of myButton_Click(...) this should be Removed by removing the following:

private void myButton_Click(object sender, RoutedEventArgs e)
{
    myButton.Content = "Clicked";
}                                        
                                    

Step 10

Once myButton_Click(...) has been removed, type the following Code below the end of the Constructor of public MainWindow() { ... }:

private readonly Library _library = new();

private void Accept_Click(object sender, RoutedEventArgs e)
{
    _library.SetLight(Display);
}

private void Clear_Click(object sender, RoutedEventArgs e)
{
    _library.ClearLight();
}                                                                                                                                                                                                                                                                  
                                    

The Method of Accept_Click will call the Method within Library.cs of SetLight from an Instance of Library called _library created with new() and Clear_Click will call the Method of ClearLight.

Step 11

Step 12

Once running you should see a Rectangle and CommandBar with the Accept and Clear options.

Step 13

You can select Apply to set the Light Effect and Clear to remove the Light Effect

Step 14