Then, your shader program main method gets called with (x, y) coordinates and expect you to return what color you want the shader to put in that location. In essence, you set up some global variables, these are normally the texture you want to shade and maybe some other texture you want to blend the first one with. Which is why modern graphics cards have to have the awesome performance they do today.
That is a lot of executions for a full screen UI running in a resolution above 1024x768. They are executed once per pixel for whatever texture or image you feed as input to them. Pixel Shaders are basically small programs that run on your graphics card rather than your main CPU. I'll not go into the finer details of Pixel Shaders in this article, other people have already created detailed documents explaining them better than I can, but I will go through the very basics of them. Sepia (well, kind of sepia I'm struggling to get it right, and it looks way too red when I do it).The different effects I've implemented for this article are:
I'll also show how to create some basic Pixel Shaders that can be controlled in a similar way (adjusting how much of the effect to use by a given factor). In this article, I'll demonstrate how to create an attached property that allows you to enable this feature using XAML, which is cool because it means you can use normal bindings to configure the properties. The annoying thing about this is that any animations or videos stop, or appear to stop (you'll find the sound of the YouTube clip you were just watching keeps going).Īs WPF allows us to apply effects to our UIElements using Pixel Shaders, it has now become easy to overcome both these limitations.
Two things about it have bugged me a bit though first, I couldn't find an easy way to do the same thing in my WinForm apps, and secondly, Windows XP seems to store an image of what the screen looked like when the dialog appeared and then drain the colour out of that. I think this looks cool and is user friendly. As this is a system dialog which has to be completed before everything else that is currently happening, the developers of Windows XP thought it would be neat if the rest of your screen slowly faded into black and white. When ever I click "Turn Off Computer" on my XP box, a dialog appears asking me if I want to Stand By, Turn Off, or Restart. These steps are discussed in more detail later in the article. Note: The sample project relies on a DirectX SDK being installed if you do not have this installed and you don't want to download it, you should still be able to compile the project by removing all the post-build steps from the project configuration. Another cool thing about using Pixel Shaders is that it makes it easy to change the type of effect applied, and in this article, I'll also show how to apply a blur effect and change the opacity.
I think this feature is quite cool as it forces the user to focus on the dialog that just popped up, and because it's possible to leverage Pixel Shaders in WPF, this can be done without storing a static image of the parent window and modifying that (which in turn allows animations to continue in the parent window as it's being grayed out). This is kind of what Windows XP does when you click "Turn off Computer". In this article, I will discuss how to use Pixel Shaders to achieve a gradient change to black and white for the parent window when a modal dialog is opened by it.