16 bit color buffer

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Christophe Bernardi (gorbalou++at++oktal.fr)
Fri, 25 Jun 1999 13:16:06 +0200

How can I increase the color buffer to 16 bit (I need only Red and
Alpha) on Performer/opengl app, and on which hardware( IR, OCTANE, O2)?

I made some tests on IR and O2:

1. with perfly -t 0xvisid and GLFORCEVISUALS set to this file sent by
Sgi:

14
# visualClass level rgb {R,G,B,A}Bits accum{R,G,B,A}Bits double stereo
indexBits depthBits stencilBits aux msamples mbuffers
#
# overlay
  4 1 1 5 5 5 1 0 0 0 0 0 0 15 0 0 0 0 0
# multisample
  4 0 3 16 0 0 16 25 0 0 25 0 0 12 23 8 0 0 0
  4 0 1 16 0 0 16 0 0 0 0 0 0 24 23 8 0 8 1
  4 0 1 10 10 10 0 32 32 32 0 1 0 24 16 8 0 8 1
  4 0 1 8 8 8 8 32 32 32 32 1 0 24 16 8 0 4 1
  4 0 1 8 8 8 8 0 0 0 0 1 0 24 15 1 0 4 1
  4 0 1 12 12 12 12 32 32 32 32 0 0 24 16 8 0 4 1
  4 0 1 10 10 10 0 0 0 0 0 1 0 24 23 1 0 4 1
  4 0 1 10 10 10 0 25 25 25 0 0 1 30 0 0 0 8 1
  4 0 1 5 5 5 1 0 0 0 0 1 0 24 15 8 0 4 1
# truecolor visuals
  4 0 1 12 12 12 12 32 32 32 32 0 0 24 23 8 0 0 0
  4 0 1 12 12 12 12 32 32 32 32 1 0 24 23 8 0 0 0
# pseudocolor visuals
  3 0 0 0 0 0 0 0 0 0 0 0 0 12 23 8 0 0 0
  3 0 0 0 0 0 0 0 0 0 0 1 0 12 23 8 0 0 0

but when I read the red buffer it's always 12 bit on IR and 8 on O2.
i.e. 1/2^12=.000244 precision on IR and 1/2^8 on O2.

I need more information/doc on the format of this file and the relation
with the output of glxinfo -fbcinfo.

2. with pbuffer but I don't know how to make the p bit in the drawable
type for glxinfo -fbcinfo

Remark: on O2 I have these visuals but they don't have Xid
0xffffffff -1 ?? . 8 . r . . 8 . . . . . . . . . . . .
p|P 0x5c
0xffffffff -1 ?? . 16 . r . . 16 . . . . . . . . . . . .
p|P 0x5d
0xffffffff -1 ?? . 64 . r . . 16 16 16 16 . . . . . . . . .
p|P 0x5e

Thanks,

-- 
  ---------------------------------
  Christophe Bernardi
  Oktal
  2, Impasse de Boudeville 31100 Toulouse
  Tel: 05 62 11 93 50
  Fax: 05 62 11 50 29
  mailto:gorbalou++at++oktal.fr
  ----------------------------------

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