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Revision as of 03:48, 23 November 2012 by r2d2rigo (Talk | contribs)

Creating a Lens application that uses HLSL effects for filters

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This article covers how to create a Lens application that applies different filters to the photos. These filters are programmed in High Level Shading Language and are executed on the GPU to take advantage of the new DirectX functionality introduced in Windows Phone 8.

Contents

Introduction

Creating the base project

Modifying the MainPage

Open a new instance of Visual Studio and create a project based on the Windows Phone App template. We will be using a standard C#/XAML application and modify it further to accustom our requirements. Start by opening the MainPage.xaml file and deleting the Grid control named LayoutRoot and all its children elements. Now create a control of type DrawingSurfaceBackgroundGrid as the page's root and give it a name (we will be calling it DrawingSurface). This is required when your application is going to use full screen mode for advanced graphics rendering through DirectX, so you don't get any performance penalties derived from the XAML composition system. You can find more info about this control in the MSDN article Direct3D with XAML apps for Windows Phone 8.

Adding SharpDX references

Instead of using the default DirectX interoperatiblity though a separate C++ DLL, we are going to use the SharpDX library to make drawing calls from C# code. This library is a wrapper of the underlying DirectX functions that allow them to be used in any .NET language and currently supports Windows Desktop, Windows Metro and Windows Phone 8. Start by heading to the downloads section and get the package of your choice: "binary only" includes the libraries and "full package" has some sample code on how to perform common tasks with SharpDX.

Create a new directory inside your project's folder called Lib. Open it and create two child folders called x86 and ARM. Decompress the package you downloaded and from the Bin folder, copy the contents of Standard-wp8-x86 to your x86 folder and Standard-wp8-ARM to ARM. In your project, right click on References and select Add References..., and in the new window click Browse and navigate to the Lib\x86 folder to select the following assemblies:

  • SharpDX.dll
  • SharpDX.DXGI.dll
  • SharpDX.Direct3D11.dll
  • SharpDX.Toolkit.dll
  • SharpDX.Toolkit.Game.dll
  • ShaprDX.Toolkit.Graphics.dll

Since the assemblies aren't AnyCPU, and currently we only have the x86 ones referenced, we must edit our project manually so the compiler references the correct ones. Close Visual Studio and open your CSPROJ file in your favourite text editor and look for the items named Reference, like this one:

<Reference Include="SharpDX">
<HintPath>Lib\x86\SharpDX.dll</HintPath>
</Reference>

You need to change the x86 part of the path to $(Platform), so it ends like this:

<Reference Include="SharpDX">
<HintPath>Lib\$(Platform)\SharpDX.dll</HintPath>
</Reference>

What we have written is a MSBuild property that gets replaced with the current platform name when building the project, so the correct version of the assemblies is used. Repeat this step for all existing references to SharpDX. When finished, save the changes and reopen the solution in Visual Studio.

Note.pngNote: If Visual Studio can't find the SharpDX references, go to the Build > Configuration Manager... menu and change Active solution platform to x86. Remember to change it again to ARM when deploying to a Windows Phone 8 device.

Application loop and basic drawing

Although we are creating a standard XAML navigation-based application, we are going to leverage some of the DirectX functionality to the framework provided by SharpDX.Toolkit. This is a collection of classes and utilities that mimics a subset of the XNA framework, and is provided as an extension to the core SharpDX libraries. If you have previous experience with XNA, you will find some of the code we are going to write very familiar.

Start by creating a new class and naming it MainLoop. Make it inherit from SharpDX.Toolkit.Game' and add a private field of type SharpDX.Toolkit.GraphicsDeviceManager. Now go to the constructor and initialize this field, passing this as the only parameter. At last, override the virtual function Draw and add the line GraphicsDevice.Clear(GraphicsDevice.BackBuffer, Color.Red); to its body. This should be the result:

public class MainLoop : Game
{
GraphicsDeviceManager deviceManager;
 
public MainLoop()
{
deviceManager = new GraphicsDeviceManager(this);
}
 
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(GraphicsDevice.BackBuffer, Color.Red);
 
base.Draw(gameTime);
}
}

When created, the GraphicsDeviceManager will fetch the appropriate graphics adapter and initialize a valid graphics device that will allow the application to issue draw calls to the screen through the DirectX runtime. This, in turn, will allow us to tell the GraphicsDevice in the Draw function to draw whatever we want; for now, we will clear the entire screen to red. Finally, to make this loop run independelty while the application is open, instantiate it in the MainPage and call its Run method with the DrawingSurfaceBackgroundGrid you created as its parameter:

public partial class MainPage : PhoneApplicationPage
{
MainLoop loop;
 
public MainPage()
{
InitializeComponent();
 
loop = new MainLoop();
loop.Run(this.DrawingSurface);
}
}

Run your application in the emulator or a device and it should display as follows:

Displaying the camera feed onscreen

Creating and drawing a DirectX texture

Capturing camera input and updating the texture

Remove Category:Draft when the page is complete or near complete


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Created: r2d2rigo (19 Nov 2012)
Last edited: r2d2rigo (23 Nov 2012)
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