Gamma problems on iR & ONYX-2 iR

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Steve Baker (sbaker++at++link.com)
Wed, 26 Nov 1997 12:06:21 -0600 (CST)


  I have been having increasing amounts of trouble with
the code I have for setting the Gamma tables. The code
is derived from something I got from someone at SGI
earlier this year.

  It seems to work OK 99% of the time on ONYX-1 iR boxes,
but fails 100% of the time on ONYX-2 iR. The symptoms in
the 1% failure on ONYX-1 are identical to the symptoms in
all cases on ONYX-2, and that is that some output colours
get mapped to peak red - while the rest of the scene comes
out OK. In the ONYX-1 case, simply re-running the program
usually fixes the problem.

  I'm using this code from within the DRAW callback:

  int chan_id = 0 ;
  int scr_id = 0 ; /* or 1 or 2 */
  int map_id = 0 ;
  int size = 4096 ;

  pfWSConnection d = pfGetCurWSConnection () ;

  XSGIvcStoreGammaColors16 ( d, scr_id, map_id, size, XSGIVC_MComponentRed , gamma_lut_r ) ;
  XSGIvcStoreGammaColors16 ( d, scr_id, map_id, size, XSGIVC_MComponentGreen, gamma_lut_g ) ;
  XSGIvcStoreGammaColors16 ( d, scr_id, map_id, size, XSGIVC_MComponentBlue , gamma_lut_b ) ;
  XSGIvcSetChannelGammaMap ( d, scr_id, chan_id, map_id ) ;

  The three gamma_lut_? arrays are all 4096 element arrays of type 'unsigned short' and
are allocated from the Performer shared memory arena. Since the code works some of the
time, I assume that there is nothing wrong with the contents of the gamma_lut_? arrays.

  The problem manifests itself on a single pipe deskside ONYX-2 running IRIX 6.4 and
Perf 2.2 a400, and also on a range of ONYX-1 configurations running IRIX 6.2 and
any of Perf 2.2 betas (including a400).

  I see the problem with the simplest single-channel, single-pipe code.

  Any ideas?

Steve Baker 817-619-8776 (Vox/Vox-Mail)
Hughes Training Inc. 817-619-4028 (Fax)
2200 Arlington Downs Road SBaker++at++link.com (eMail)
Arlington, Texas. TX 76005-6171 SJBaker1++at++airmail.net (Personal eMail)
http://www.hti.com http://web2.airmail.net/sjbaker1 (personal)

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