Re: [Mesa3d-users] Getting GLUT to work with OSMesa

[Brian P. <bri...@tu...>]

Alexander Mont wrote:
> You may have misunderstood what I was attempting to do.
> 
> I do not want to have *two* separate rendering contexts: one for the
> offscreen rendering and one for the onscreen rendering. Rather, I want to
> have a *single* offscreen rendering context, but I want the GLUT display
> functionality to still work.
> 
> The attached file is a simple test program that explains what I am
> attempting to do. The OSTEST preprocessor definition controls whether OSMesa
> is used, while the CREATEWINDOW preprocessor definition controls whether
> GLUTCreateWindow is called.
> 
> If OSTEST is turned off, it is a simple GLUT application that uses the
> window, and it works correctly. If OSTEST is turned on, what I am doing is
> creating the window, then switching the rendering context to the OSMesa one.
> In this case, when I run the program, a window comes up, which appears
> broken. If you wait several seconds and then close the window, however, the
> files will have come up as desired.
> 
> What I want to do is have exactly this behavior, except for it not to have
> to create an actual window at all. This is because I want to run it on a
> machine (such as a cluster node) that does not have a windowing system. If I
> try to avoid creating the window by simply removing the call to
> GLUTCreateWindow() (which can be done in this test program by removing the
> #define CREATEWINDOW) then the program immediately fails with an access
> violation when glutMainLoop() is called.
> 
> Is it even possible to use GLUT without creating an actual window, and if so
> how?

No, I don't think that's possible.  I seem to recall that GLUT should 
issue an error message if you try to enter the main loop without 
creating a window.


> (It is possible that the only way to do this would be to modify the GLUT
> libraries that come with Mesa. If that is the case, then I would be willing
> to submit any modifications I make back to the Mesa project so that other
> users who desire the same functionality could use it.)

I guess what I'm wondering is this: why make any GLUT calls at all if 
you're just going to use OSMesa to render to an off-screen buffer?

-Brian