DirectX Core App versus XAML + DirectX app

Question

I recently tried both versions of porting my DirectX11 C++ engine to windows store apps.

The first version involves creating the SwapChain yourself, and then rendering stuff, pretty straight forward if you're coming from a Win32 background as I do.

The second option, with XAML involves something a bit weird : recreating the backbuffer render target AT EVERY FRAME. Seriously, why is this needed ?

Initially I was like OK, let's see if this problem has a performance hit.

And today I realized the performance penalty is around 40% (going from 50FPS with XAML to 70FPS without)  on my GTX 560 Ti for a 1920x1080 engine running 100+ dinstinct shaders in a scene, so it's a pretty heavy workload for the GPU. This is also on a Core i7 2600 so the CPU bottlenecking the performance is just out of the question. The XAML I had only involved 3 buttons and a TextBlock, so it wasn't all that heavy really.

Now, the thing is that I wanted some windows 8 style buttons ontop of my app, to integrate well with the system, but if that's going to eat 40% of the performance I'd rather write some simple shaders to render squares and I'm done.

Why has microsoft taken such a low-performance route though ?

Answer 1

Look at the Direct2D+XAML template app in VS2012. It uses a SwapChainBackgroundPanel and doesn't require recreating the render target each frame.

Answer 2

You may also take a look this blog titled "Combining XAML and DirectX" at http://blogs.msdn.com/b/windowsappdev/archive/2012/03/15/combining-xaml-and-directx.aspx.

For a commercial Windows store app, XAML+DirectX may be the only way to go. A pure DirectX app using CoreWindow is useless, who need an app with no user interaction after all?

Answer 3

You may also take a look this blog titled "Combining XAML and DirectX" at http://blogs.msdn.com/b/windowsappdev/archive/2012/03/15/combining-xaml-and-directx.aspx.

For a commercial Windows store app, XAML+DirectX may be the only way to go. A pure DirectX app using CoreWindow is useless, who need an app with no user interaction after all?

I don't know where you got your info but I just checked and CoreWindow has event handlers you can set up from C++ code. There's a variable called PointerCursor which the documentation says it's used for both mouse arrow and touch device, and then you have something like this :

window->PointerPressed += ref new TypedEventHandler<CoreWindow^, PointerEventArgs^>(this, &Windows8App::OnPointerPressed);
window->PointerMoved += ref new TypedEventHandler<CoreWindow^, PointerEventArgs^>(this, &Windows8App::OnPointerMoved);
window->PointerReleased += ref new TypedEventHandler<CoreWindow^, PointerEventArgs^>(this, &Windows8App::OnPointerReleased);
window->CharacterReceived += ref new TypedEventHandler<CoreWindow^, CharacterReceivedEventArgs^>(this, &Windows8App::CharacterReceived);
	

So there you go, mouse/touch and keyboard input :)
   

Answer 4

The pointer (mouse/touch/stylus) input is only useful when users are presented with XAML controls. Without XAML, how can you show an application about dialog to the users?

Answer 5

The pointer (mouse/touch/stylus) input is only useful when users are presented with XAML controls. Without XAML, how can you show an application about dialog to the users?

I could simply render a polygon with text on top, would look like a dialog. So where's the problem, again? :) And I agree with Skyrape, XAML + D3D is slower than D3D.... sadly.

Answer 6

Yesterday I looked at a laptop with Core i3 and Windows 8. I clicked on the store app and man, it took ~1 minute to start. Now what does the store have that it takes so much to load ? Just an array of rectangles. Given the low performance I could make my own Windows 8 look-alike rendering library. It's just a bunch of rectangles in the end, and I wouldn't be surprised if someone makes this eventually.

Answer 7

Yesterday I looked at a laptop with Core i3 and Windows 8. I clicked on the store app and man, it took ~1 minute to start. Now what does the store have that it takes so much to load ? Just an array of rectangles. Given the low performance I could make my own Windows 8 look-alike rendering library. It's just a bunch of rectangles in the end, and I wouldn't be surprised if someone makes this eventually.

That's obviously due to some sort of internet problem or whatever, not any XAML or other GPU-related activity. My Metro app had several complex vertex and pixel shaders and it ran just fine on a Samsung Slate 7, which has a lower perf GPU than new Core CPUs.

There are several valid complaints about WinRT you can make ... but rendering performance isn't one of them.

Answer 8

Hello,

I would like to change this thread type as discussion, because I think there may be no exact answer for this question.

Thanks for your understanding,

Best regards,
Jesse

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Jesse Jiang
MSDN Community Support | Feedback to us
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