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Re: OpenGL rendering in background

To: comp@xxxxxxx
Subject: Re: OpenGL rendering in background
From: Dave Shreiner <shreiner@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 29 Jul 2004 12:45:00 -0700
Cc: ogl-sample@xxxxxxxxxxx
In-reply-to: <32802.>
References: <32802.>
Sender: ogl-sample-bounce@xxxxxxxxxxx
User-agent: Mutt/
Hi Peter,

> It is possible to use OpenGL without any window manager (e.g. not
> attaching to a drawing context with wglsetcurrent/glxsetcurrent)?

   Since I think the question you're asking is whether it's possible to
open an OpenGL window without a windowing system, the answer is: it
depends.  WGL, GLX, and any or the other "binding" libraries are what
OpenGL requires in order to configure the framebuffer for rendering.
The windowing system manages the allocation of framebuffer resources,
and then binding an OpenGL context enables OpenGL to use that bit of
system resources.

   I'm personally not aware of hardware accelerated solutions that do
not use a windowing system.

> We need background rendering without user interface. The generated images
> are copied from the display buffer and postprocessed by our app.

   Are you reallying looking for hardware-accelerated, off-screen
rendering areas?  These are termed pixel-buffers, and supported in many
windowing systems.  I'm not much of a Windows savant, but you can query
and configure them using glXQueryFBConfigs() for GLX 1.3.

> How to do this? Which OpenGL settings needed to enable background rendering?

   Much of this is described in the OpenGL Red and Blue books, and ample
source code is available from opengl.org.

   Hope that helps.




   Dave Shreiner                                   <shreiner@xxxxxxx>
   Silicon Graphics, Inc.                            (650) 933-4899

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