art with code

2009-04-01

And now glReadPixels works on ATI pbuffer

glReadPixels from a pbuffer didn't work on a Radeon 9600 with the Linux fglrx drivers. And it was a very strange bug. Apparently pbuffer contexts don't work on ATI fglrx + R300 if you don't first create a X window context and make it current. Here's the code for the fix in nsGLPbufferGLX::Init:

// workaround for Radeon 9600 pbuffers contexts not working without a
// previous window context
XVisualInfo *visinfo;
int vattrib[] = { GLX_RGBA, None };
visinfo = gGLXWrap.fChooseVisual( sharedDisplay, DefaultScreen(sharedDisplay), vattrib );
workaroundCtx = gGLXWrap.fCreateContext( sharedDisplay, visinfo, NULL, GL_TRUE );
gGLXWrap.fMakeContextCurrent(
sharedDisplay,
DefaultRootWindow(sharedDisplay),
DefaultRootWindow(sharedDisplay),
workaroundCtx );
XFree(visinfo);

Now my Canvas 3D demos work on ATI + Linux, yay!
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Built art installations, web sites, graphics libraries, web browsers, mobile apps, desktop apps, media player themes, many nutty prototypes