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GLX_SGIX_hyperpipe	    OpenGL Reference - GLX	    GLX_SGIX_hyperpipe

NAME    [Toc]    [Back]

     GLX_SGIX_hyperpipe	- hyperpipe extension

DESCRIPTION    [Toc]    [Back]

     Even though graphics hardware is constantly improving in speed, there
     will always be applications that require more performance than is
     available from a single pipeline. In order	to overcome these limits, it
     is	possible to parallelize	the rendering task across multiple pipes; the
     image outputs of these pipes must then be assembled into a	single display
     output. This group	of pipes is termed a hyperpipe;	the pipes involved
     must be physically	cabled together	in some	way to form a hyperpipe
     network. Typically	a hyperpipe network uses one of	the pipes to assemble
     the rendered images and drive the display.

     In	a hyperpipe network, the rendering task	may be divided by rendering
     each successive frame on a	different hardware pipe	(temporal division);
     by	dividing the frame into	rectangular subregions and rendering each on a
     different pipe (spatial division);	or by a	combination of these two
     techniques. Specific hardware implementations may impose limits on	how
     rendering may be subdivided; but in general it is possible	to use a
     subset of the pipes connected to a	hyperpipe network if desired.

     This extension provides a means for configuring and managing a group of
     rendering pipes which work	together to produce a single display.
     Typically,	a hyperpipe application	will be	multi threaded,	with one
     thread per	pipe; each thread needs	to create its own rendering context.
     The hyperpipe extension allows these rendering threads to communicate
     with the hardware.

     The API calls allow an application	to:

     o	Determine the physical configuration of	a hyperpipe network.

     o	Configure the hyperpipe. The hyperpipe configuration used by the
	application may	be a subset of the physical hyperpipe network.
	The rendering task may be divided in time slices (temporally divided),
	in rectangular regions of a single frame (spatially divided), or both.
	The hyperpipe configuration is subject to hardware constraints.

	For example, on	a hyperpipe network consisting of five pipes, it
	would be possible to configure a rendering task	in two time slices,
	with each slice	being rendered by two pipes; thus using	four total
	pipes. (The fifth pipe would not be used in the	hyperpipe, and
	could be used for normal non-hyperpipe rendering and display).

     o	Maintain state to manage the glXSwapBuffers  call correctly. In
	spatial	subdivision, swap cannot occur until all pipes rendering
	the next frame have completed; and in temporal subdivision, swap
	cannot occur until the appropriate time. Swap management is
	handled	by the displaying pipe.

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GLX_SGIX_hyperpipe	    OpenGL Reference - GLX	    GLX_SGIX_hyperpipe

     o	Redirect resize	parameters correctly; typically	resize is handled
	by the displaying pipe,	and must be managed synchronously with

     o	Balance	load among the pipes in	the spatial subdivision	case.

     o	Clean up operations when a hyperpipe application terminates
	(either	normally or due	to error).

     This extension adds to the	set of conditions that must be met before a
     buffer swap can take place.

FUNCTIONS    [Toc]    [Back]

     The main functions	are:

     glXQueryHyperpipeNetworkSGIX - query the physical hyperpipe network.

     glXHyperpipeConfigSGIX - configure	the hyperpipe network.

     glXQueryHyperpipeConfigSGIX - query a particular hyperpipe	configuration.

     glXDestroyHyperpipeConfigSGIX - destroy a hyperpipe configuration.

     glXBindHyperpipeSGIX - bind a process and rendering context to a
     hyperpipe configuration.

NOTES    [Toc]    [Back]

     In	addition to its	usual functionality, the glXSwapBuffers	call on	a
     rendering context bound to	a hyperpipe causes the hyperpipe display
     output to switch to the next pipe of the network.

     Hyperpipes	cannot function	on single buffered visuals; double buffered
     visuals are required on all bound graphics	contexts.

     The hyperpipe id associated with a	context	can be determined by calling
     glXQueryContextInfoEXT with an attribute of GLX_HYPERPIPE_ID_SGIX.

SAMPLE CODE    [Toc]    [Back]

     Typically,	a hyperpipe application	will have a master process which:

     o Queries the hyperpipe network;

     o Chooses which of	the pipes on the hyperpipe network to use;

     o Sets up a hyperpipe configuration using the above pipes;

     o Forks off one (or more) rendering processes per pipe.

     Each of the created child processes will:

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GLX_SGIX_hyperpipe	    OpenGL Reference - GLX	    GLX_SGIX_hyperpipe

     o Create its own window and a direct rendering graphics context;

     o Binds the rendering context to the hyperpipe id supplied	by
       the master process.

     Master Process

	  GLXHyperpipeNetworkSGIX * nw;
	  GLXHyperpipeConfigSGIX cfg[32];
	  char * extString;

	  /* Open the default display */
	  dpy =	XOpenDisplay( 0	);

	  scr =	DefaultScreen( dpy );

	  /* Query the extension string	to verify that the
	  ** hyperpipe extension is present

	  extString = (char *)glXQueryExtensionsString(dpy,scr);

	  if (!strstr( extString, "GLX_SGIX_hyperpipe")) {
	       /* Abort	*/

	  /* Query the hyperpipe network */

	  nw  =	glXQueryHyperpipeNetworkSGIX(dpy, &npipes);
	  if ( (nw== NULL) || (npipes == 0 ) ) {
	       /* No hyperpipe network,	Abort */

	  /* Choose some pipes from the	above list in nw and fill in the
	  ** configuration structure
	  ** The sample	code below sets	up a 3 pipe hyperpipe

	  nid =	nw[0].networkId;
	  npipes = 2;

	  for (i=0; i<npipes; i++) {

	       strcpy (cfg[i].pipeName,	nw[i].pipeName);
	       cfg[i].participationType	= GLX_HYPERPIPE_RENDER_PIPE_SGIX;
	       cfg[i].timeSlice	= i;
	       cfg[i].channel =	0;

	  /* Choose the	first pipe to be the display pipe also */

	  cfg[0].participationType |=  GLX_HYPERPIPE_DISPLAY_PIPE_SGIX;

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GLX_SGIX_hyperpipe	    OpenGL Reference - GLX	    GLX_SGIX_hyperpipe

	  if (glXHyperpipeConfigSGIX( dpy,

	       /*Something wrong with the hyperpipe configuration;Abort	*/

	  /* Don't need	the hyperpipe network information any more */

	  XFree	(nw);

	  /*Now	fork npipes number of process */

	  /* hang around untill	all child processes finish */
	  glXDestroyHyperpipeConfigSGIX(dpy, hpId);

     Each child	process	then calls :

	  /* Open Display and screen */

	  /* sanity checking to	ensure that the	hyperpipe
	  ** is	present	on the required	pipes

	  extString = (char *)glXQueryExtensionsString(dpy,scr);
	  if (!strstr( extString, "GLX_SGIX_hyperpipe")) {

	       /* Abort	*/

	  /* Create a direct rendering context and make	it current */

	  if (glXBindHyperpipeSGIX (dpy, hpId) {

	       /* Error	in bind; Abort */

	  /* Render */


	  /* All done */

	  glXBindHyperpipeSGIX(dpy, -1);

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GLX_SGIX_hyperpipe	    OpenGL Reference - GLX	    GLX_SGIX_hyperpipe

SEE ALSO    [Toc]    [Back]

     glXQueryHyperpipeNetworkSGIX(), glXHyperpipeConfigSGIX(),
     glXQueryHyperpipeConfigSGIX(), glXDestroyHyperpipeConfigSGIX(),

									PPPPaaaaggggeeee 5555
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