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Thread: Transparent Window Demo

  1. #21
    Junior Member Newbie
    Join Date
    Oct 2003

    Re: Transparent Window Demo

    The crashes on NV cards are from a line of code I forgot to remove while fixing the earlier ATI problem. This has been fixed. My apologies for any frustration this has caused.

    @kehziah: Yes, the executable was a little large. I made some changes and reduced it to around 268K. As for the dlls, I haven't figured out how to statically link to the Cg runtime. I know it was possible with the beta version of the Cg libraries, but I haven't had much time to learn how to do it now. Does any one else know?

    Also, the demo uses ARB FP1 and VP1 for per-pixel lighting. IIRC the 8500 supports only the ATI fragment shader extension. I may add support for PPL on a broader range of hardware in the future, but using ARB FP/VP was a time vs. necessity choice--this is a demonstration of transparent windows, after all.

    I've only had a few complaints since I broke the demo for NV hardware. The implications of that are interesting.

    Thanks again for the responses,


  2. #22
    Junior Member Regular Contributor
    Join Date
    Jan 2003

    Re: Transparent Window Demo

    I tried running a normal OpenGL demo along with your demo, and
    everything slowed down horribly to a snail's pace. And the windows area
    where the two demos intersected was not drawn.

    Found some info on a Google search. It seems using layered windows
    and OpenGL/DirectX is not recommended by Microsoft:

    From: Greg Binkerd [MS] (
    Subject: RE: WS_EX_LAYERED and OpenGL together?
    View: Complete Thread (3 articles)
    Original Format
    Newsgroups: microsoft.public.win32.programmer.gdi
    Date: 2002-06-05 10:18:55 PST

    Hi, Craig.

    Unfortunately, OpenGL (and DirectX) can not be used in a layered window.
    The hardware performs all rendering and will not incorporate the
    semitransparency effect displayed by a layered window. In fact, if you
    create a layered window and you move it over an OpenGL application or
    windowed DirectX application, you will see "flashing" of the layered
    window, since the hardware will draw the 3D primitives directly on the
    primary surface, drawing over the layered window and the layered window
    will immediately redraw itself in a semitransparent state. Note, this will
    only occur with hardware accelerated OpenGL and DirectX applications.

    Microsoft Developer Support

  3. #23
    Intern Newbie
    Join Date
    May 2003

    Re: Transparent Window Demo

    I know it may be slow, but couldn't this
    problem be solved by rendering into a texture,
    then using glGetTexImage to get the result of
    the rendering and then blit this result on
    the surface of the window as a GDI bitmap ?

  4. #24
    Junior Member Newbie
    Join Date
    Oct 2003

    Re: Transparent Window Demo

    @gator: I've noticed this slowdown too. This appears to be related to using pbuffers, but the frequency of updates to the layered window probably contributes. Try any of the ATI or nVidia pbuffer demos along with the demo you mentioned and you will see a similar, although possibly less pronounced, effect. I've noticed that most consumer level cards are not very good with multiple OpenGL contexts, especially ones using extended functionality. Hopefully this will change in the near future.

    It seems using layered windows
    and OpenGL/DirectX is not recommended by Microsoft
    Yes, in fact trying to create a context on a layered window will bring your system down in XP. However, this demo does not mix the two, it simply uses OpenGL to generate the image information for the layered window--the layered window does not have an associated context. As for the flickering, that is the situation with all layered windows. Try animating another layered window app, such as WMP, over an OpenGL app and you will see similar effects.

  5. #25
    Junior Member Newbie
    Join Date
    Feb 2007
    Florianopolis - Brazil

    Re: Transparent Window Demo

    There's nothing like reviving an old thread! @Dude, we are still waiting for the Cube's code.

    Meanwhile, you guys can check this thread on StackOverflow:

    Even though it's probably not the technique used by the Cube demo, it has a working source code that achieves the same effect.

  6. #26
    Senior Member OpenGL Lord
    Join Date
    May 2009

    Re: Transparent Window Demo

    This thread is 7 years old. The stuff it's talking about is oudated, and the people who posted here haven't posted for years.

    You're talking to nobody.

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