[vtkusers] Windows offscreen image rendering

John Biddiscombe jbiddiscombe at skippingmouse.co.uk
Mon Sep 10 05:18:27 EDT 2001

 From the list a few weeks ago.....the offscreen renderwindow sounds like 
what you want, but I for one know nothing about it.


Date: Thu, 9 Aug 2001 12:51:52 -0500 (CDT)
From: Tony Lavoie <lavoie at mcs.anl.gov>
To: vtkusers at public.kitware.com
Subject: Re: [vtkusers] About OffScreen Question ^_^
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I went looking int off-screen rendering as well, and I tried the
vtkOffScreen code. First, on Linux (Unix/OpenGL/X11 systems as it says),
it links against the Mesa libs, which has offscreen rendering if you
glance through vtkMesaRenderWindow.cxx. I looked into OpenGL support of
offscreen rendering, and found that the blue book (OpenGL Reference
Manual, OpenGL ARB) says that pbuffers and pixmaps are only implemented in
GLX 1.3, and 1.3 afaik is only available for SGI's- 1.3 for Linux & Mac is
"Coming Soon..."

-Tony . o O ( c'mon nVidia, GLX 1.3 on GeForce3's!! )

On Thu, 9 Aug 2001, David Homiak wrote:

 > Kevin,
 >       See http://infinite-entropy.lbl.gov/VTK/vtkOffScreen/ for a
 > vtkOpenGLOffscreenRenderWindow class. From there description:
 >       "Use in place of a vtkRenderWindow to draw an offscreen image. This
 > is specifically for Unix/OpenGL/X11 systems. There is already a
 > vtkWin32OffscreenRenderWindow in the contrib directory of VTK to cover
 > Windows systems. For SGI systems, it will use pbuffers for hardware
 > accelerated offscreen rendering. For all other architectures, it will use
 > GLX pixmaps which tend to be software-rendering (except for
 > hardware-accelerated Mesa)."
 >       More generally for X11 on UNIX, there is also Xvfb, the X virtual
 > frame buffer. Do a Google search on it and also check out
 > http://starbase.neosoft.com/~claird/comp.windows.x/Xvfb.html. I have used
 > Xvfb in the past to do X processing on headless Sun servers lacking graphics
 > cards.
 > Dave Homiak
 > dhomiak at xcaliber.com
 > Results! Why, man, I have gotten a lot of results. I know several thousand
 > things that won't work.    --   Thomas Edison
 > > Date: Wed, 08 Aug 2001 17:22:20 +0800
 > > From: Lin Sun-In <lsi at nchc.gov.tw>
 > > To: vtkusers at public.kitware.com
 > > Subject: [vtkusers] About OffScreen Question ^_^
 > >
 > > Dear VTK author:
 > >
 > >     I have a problem about VTK. We know OpenGL fo Win32 has support
 > > offscreen function , and VTK for Win32 also provide similar functions.
 > > But now I want to try this feature in Unix-like platform, but i have no
 > > idea. Could you please tell me any solution about this.
 > >
 > > PS : Because I want to run VTK program in the background, but the
 > > RenderWindow need a X-Window Server to display the result. So I must
 > > login to take a window manager or set the "DISPLAY" environment variable
 > > to transfer the display to another machine. But I want to have the same
 > > function in Win32 OS ==> "offscreen". Could you please tell me how can i
 > > do it ????
 > >
 > >                             Kevin
 > _______________________________________________
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At 12:53 09/09/2001, =?utf-8?Q?Ermin_Hasi=C4=8Devi=C4=87?= wrote:
>         -----Original Message-----
>         From: John Biddiscombe
>         Sent: sub 08.09.01 19:04
>         To: Ermin Hasičević; vtkusers at public.kitware.com
>         Cc:
>         Subject: Re: [vtkusers] Windows offscreen image rendering
>              renWin->SetupMemoryRendering(width, height,
>         (HDC)renWin->GetGenericContext());
>              renWin->Render();
>         // do stuff with bitmap
>              renWin->ResumeScreenRendering();
>         > have used this successfully, but note that it stopped working
>some time
>         >(I don't know when - I didn't use it for months) and when I
>tried it last
>         >week it gave an image of width & height of zero (ie nothing). I
>checked in
>         >a fix a few days ago and my offscreen rendering is working fine
>         >maybe you should try a nightly release from today or similar
>and give it a go.
>         >
>         >If you're using an older vtk, you should probably just get
>         >vtkWin32OpenGLRenderWindow from cvs
>         >(Note that the above assumes you already have a compatible
>device context
>         >on screen, if you are doing vtk without a window you might need
>         >else...)
>         >JB
>         I don't know if I misunderstood concept of offscreen rendering,
>but I thought
>         that it's such kind of rendering where no image window pops out
>when I start
>         image rendering. Is there any way to tell vtkWin32OpenGLImage
>window to
>         not show when I call render method for first time or there's no
>hope to get away
>         from that?
>         Ermin

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