Session – WPF: Extensible BitmapEffects, Pixel Shaders, and WPF Graphics Futures

PDC 2008, Day #4, Session #4, 1 hr 15 mins

David Teitlebaum
Program Manager
WPF Team

My final session at PDC 2008 was a talk about the improvements in WPF graphics that are available in .NET Framework 3.5 SP1.  David also touched briefly some possible future features (i.e. that would appear in .NET Framework 4.0).

David’s main topic was to walk through the details of the new Shader Effects model, which replaces the old Bitmap Effects feature.

What are Bitmap Effects?

These are effects that are applied to an individual UI element, like a button, to create some desired visual effect.  This includes things like drop shadow, bevels and blur effects.


The BitmapEffect object was introduced in Framework 3.0 (the first WPF release).  But there were some problems with it, that led to now replacing it with Shader Effects in 3.5SP1.

Problems with BitmapEffect:

  • They were rendered in software
  • Blur operations were very slow
  • There were various limitations, including no ClearType support, no anisotripic filtering, etc.

New Shader Effects

Basic characteristics in the new Shader Effects include:

  • GPU accelerated
  • Have implemented hardware acceleration of the most popular bitmap effects
    • But did not implement outer glow
  • Can author custom hardware-accelerated bitmap effects using HLSL
  • There is a software-only fallback pipeline that is actually faster than the old Bitmap Effects
  • New Shader Effects run on most video cards
    • Require PixelShader 2.0, which is about 5 years old

How Do You Do Shader Effects?

Here’s an outline of how you use the new Shader Effect model:

  • Derive a custom class from the new ShaderEffect class (which derives from Effect)
  • You write your actual pixel shader code in HLSL, which is used for doing custom hardware-accelerated stuff using Direct3D
    • Language is C-like
    • Compiled to byte-code, consumed by video driver, runs on GPU
  • Some more details about HLSL, as used in WPF
    • DirectX 10 supports HLSL 4.0
    • WPF currently only supports Pixelshader 2.0

So what do pixel shaders really do?  They basically take in a texture (bitmap) as input, do some processing on each point, and return a revised texture as an output.

Basically, you have a main function that accepts the coordinates of the current single pixel to be mapped.  Your code then accesses the original input texture through a register, so it just uses the input parameter (X/Y coordinate) to index into the source texture.  It then does some processing on the pixel in question and returns a color value.  This resultant color value just represents—the resulting RGB color at the specified coordinate.

The final step is to create, in managed code, a class that derives from ShaderEffect and hook it up to the pixel shader code (e.g. file) that you wrote.  You can then apply your shader to any WPF UIElement using XAML.  (By setting the Effect property).

Direct3D Interop

David’s next topic was to talk a bit about interop’ing with Direct3D.  This just means that your WPF application can easily host Direct3D content by using a new class called D3DImage.

This was pretty cool.  David demoed displaying a Direct3D wireframe in the background (WPF 3D subsystem can’t do wireframes), with WPF GUI elements in the foreground, overlaying the background image.

The basic idea is that you create a Direct3D device in unmanaged code and then hook it to a new instance of a WPF D3DImage element, which you include in your visual hierarchy.

WPF Futures

Finally, David touched very briefly on some possible future features.  These are things that may show up in WPF 4.0 (.NET Framework 4.0), or possibly beyond that.

Some of the features likely included in WPF 4.0 include:

  • Increased graphical richness  (e.g. Pixelshader 3.0)
  • Offloading more work to the GPU
  • Better rendering quality
    • Integrate DirectWrite for text clarity
    • Layout rounding

And some of the possible post-4.0 features include:

  • Better exploitation of hardware
  • Vertex shaders
  • Shader groups
  • Shaders in WPF 3D
  • 3D improvements
  • Better media extensibility


You can get at David’s PDC08 slide deck for this talk here:

And you can find full video from the session at:


Session – Windows 7: Unlocking the GPU with Direct3D

PDC 2008, Day #4, Session #3, 1 hr 15 mins

Allison Klein

I jumped off the Azure track (starting to be a bit repetitive) and next went to a session focused on Direct3D.

Despite the title, this session really had nothing to do with Windows 7, other than the fact that it talked a  lot about Direct3D 11, which will be included in Windows 7 and available for Windows Vista.

Direct3D 10

Direct3D 10 is the currently shipping version, and supported by most (all?) modern video cards, as well as integrated graphics chips.  I’m not entirely sure, but I think that Direct3D 10 shipped out-of-the-box with Windows Vista.  It is also available for Windows XP.

Allison spent about half of the talk going through things that are different in Direct3D 10, as compared with Direct3D 9.

I’m not inclined to rehash all of the details.  (I’ll include a link to Allison’s slide deck when it is available).

The main takeaway was that it’s very much worth programming to the v10 API, as opposed to the v9 API.  Some of the reasons for this include:

  • Much more consistent behavior, across devices
  • Cleaner API
  • Elimination of large CAPS (device capability) matrix, for a more consistent experience across devices
  • Built-in driver that allows D3D10 to talk to D3D9 hardware
  • Addition of WARP 10 software rasterizer, to support devices that don’t support WDDM directly.  This is actually quite a bit faster than earlier software-only implementations

Direct3D 11

In the second half of her talk, Allison talked about the advances coming in Direct3D 11.  She mentioned that D3D11 will ship with Windows 7 and also be available for Windows Vista.

Again, the details are probably more appropriate for a game developer.  (See the slide deck).  But the high level points are:

  • Direct3D 11 is a strict superset of 10—there are no changes to existing 10 features
  • Better support for character authoring, for denser meshes and more detailed characters
  • Addition of tessellation to the rendering pipeline, for better performance and quality
  • Much more scalable multi-threading support.
    • Much more flexibility in what can be distributed across threads
  • Dynamically linking in custom shaders
  • Introduction of object-oriented features (interfaces/classes) to HLSL
  • New block compression
  • Direct3D11 will be available in the Nov 2008 SDK


Finally, Allison touched briefly on some future directions that the Direct3D is thinking about.

The main topic that she talked about here was in potentially using the GPU to perform highly parallel general purpose compute intensive tasks.  The developer would use HLSL to write a “compute shader”, which would then get sent to the GPU to do the work.  As an example, she talked about using this mechanism for post-processing of an image.