GLX_SGIX_hyperpipe OpenGL Reference - GLX GLX_SGIX_hyperpipe
NAME
GLX_SGIX_hyperpipe - hyperpipe extension
DESCRIPTION
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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o Redirect resize parameters correctly; typically resize is handled
by the displaying pipe, and must be managed synchronously with
swap.
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
The main functions are:
glXQueryHyperpipeNetworkSGIX - query the physical hyperpipe network.
glXHyperpipeConfigSGIX - configure the hyperpipe network.
glXQueryHyperpipeConfigSGIX - query a particular hyperpipe configuration.
glXHyperpipeAttribSGIX - set hyperpipe attributes.
glXQueryHyperpipeAttribSGIX - query current hyperpipe attributes.
glXQueryHyperpipeBestAttribSGIX - query best hyperpipe attributes.
glXDestroyHyperpipeConfigSGIX - destroy a hyperpipe configuration.
glXBindHyperpipeSGIX - bind a process and rendering context to a
hyperpipe configuration.
NOTES
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
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;
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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:
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;
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cfg[i].channel = 0;
}
/* Choose the first pipe to be the display pipe also */
cfg[0].participationType |= GLX_HYPERPIPE_DISPLAY_PIPE_SGIX;
if (glXHyperpipeConfigSGIX( dpy,
nw[0].networkId,
npipes,
cfg,
&hpId)
== GLX_BAD_HYPERPIPE_CONFIG_SGIX) {
/*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 */
}
/* Set hyperpipe attributes dynamically */
glXHyperpipeAttribSGIX (dpy, timeSlice, attrib, size, &attribList);
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/* Render */
glXSwapBuffers(...);
/* All done */
glXBindHyperpipeSGIX(dpy, -1);
SEE ALSOglXQueryHyperpipeNetworkSGIX(), glXHyperpipeConfigSGIX(),
glXQueryHyperpipeConfigSGIX(), glXDestroyHyperpipeConfigSGIX(),
glXBindHyperpipeSGIX()
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