Masanori Kakimoto (kaki++at++kaki.nsg.sgi.com)
Wed, 11 Oct 1995 14:29:00 +0900
They use a pfMultipipe(3) call and three calls of pfNewChan, each of which
is for each pipe. They have three physical displays, each of them assigned
to each channel, or pipe. The channel for the middle display is the master.
The other two channels are pfAttachChan'ed.
The problem is that the attached channels, i.e. left and right displays,
seem to be constantly delayed by 1 frame compared to the master channel.
This is true even when the master channel renders most of the polygons and
the attached channels render much less.
The delay is even more outstanding when the frame rate is reduced by
changing the parameter for pfFrameRate. The delay is easily noticed by
moving the camera position vertically and watching the crosspoint of a
redered horizontal line and a physical boundary of the displays.
When they, instead of multipipe, tried using single pipe and multichannel
with MCO, they do NOT have the problem.
The skeleton of the main loop in the source looks like the following.
while (running) {
switch (eventHandling()) { /* pfChanView is called under this. */
case END_EVENT:
running = 0;
break;
case NEED_ISECT_EVENT:
if (Needed) {
isectProcessing(Scene); /* pfSegsIsectNode is called inside */
}
continue;
default:
break;
}
if (running) {
pfSync();
pfFrame();
}
}
They tried GangDraw using PFCHAN_SWAPBUFFERS_HW and proper wire connections
and terminations but had the same result.
They also tried CPU locking, which made no difference.
Their Onyx has 8 CPU's each of which should be assigned for Unix, APP, (CULL
and DRAW)*3 just respectively by their call
pfMultiprocess(PFMP_APP_CULL_DRAW).
Does anybody have any suggestions? Thanks in advance.
-- Masanori Kakimoto mailto:kaki++at++nsg.sgi.com East Asia Technology Center, Tokyo Office, c/o Nihon Silicon Graphics K.K. TEL:+81-3-5488-1852 FAX:+81-3-5420-2397 Voicemail:5-7465
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