Re: multisample configurations ?

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Rob Jenkins (robj++at++barney.reading.sgi.com)
Thu, 21 Dec 1995 16:19:26 +0000

On Dec 21, 8:26am, Rainer Krampe wrote:
> Subject: multisample configurations ?
> Hello,
>
> how does one change the default number (8) of multisamples in
> Performer 1.2 ?
>
> What will be the general performance gain if changed to 4 ?
>
> --
> Rainer Krampe Daimler-Benz Aerospace
> Military Aircraft
> Phone: (+89) 607 28196 P.O.Box 80 11 60
> Fax: (+89) 607 22491 D-81663 Muenchen
> E-mail: rainer.krampe++at++lm.otn.dasa.de
>-- End of excerpt from Rainer Krampe

Performer will only acheive 8 samples if you have enough framebuffer, below is
a useful table ( courtesy of Allan Schaffer I think ):

One RM is enough for:

640x512 resolution 16 samples 8 bits/component 24-bit Z
640x512 resolution 8 samples 12 bits/component 32-bit Z
960x680 resolution 8/4 samples 12 bits/component 32-bit Z
1280x1024 resolution 0 samples 12 bits/component 32-bit Z

Two RMs are enough for:

1280x1024 resolution 8 samples 8 bits/component 24-bit Z
1280x1024 resolution 4 samples 12 bits/component 32-bit Z
1600x1200 resolution 0 samples 12 bits/component 32-bit Z

Four RMs are enough for:

1280x1024 resolution 16 samples 8 bits/component 24-bit Z
1280x1024 resolution 8 samples 12 bits/component 32-bit Z
1600x1200 resolution 8 samples 8 bits/component 24-bit Z
1600x1200 resolution 4 samples 12 bits/component 32-bit Z

you can force the use of 4 samples by doing something like:

    pfInitGfx();
    zbuffer(FALSE);
    zbsize(0);
    mssize(4,32,1); or 2,24,0 or whatever.

I don't know what performance gain you'd get if at all but I guess it would be
easy to measure ( and depends how close to a frame boundary your draw time is
).

The main advantage I can see is that for example on a 2RM machine you might
achieve 8 samples but only get 8 bits per color component and 24 bit zbuffer (
the man page for pfAntiAlias discusses what Performer tries to do ). If you
forced 4 bits you could have 12 bits/comp colours and 32 bit z. When you do any
RE framebuffer config *always* find out what you actually did get with
getgconfig(..).

gldebug is also useful to check what GL calls are happening where.

Cheers
Rob

************************ Happy Christmas and New Year ************************

-- 
________________________________________________________________
Rob Jenkins, Software Support Group, Silicon Graphics UK Ltd.       
Forum 1, Station Road, Theale, Reading, UK, RG7 4SB. 
tel 01734 257736, fax 01734 257553, email robj++at++reading.sgi.com,

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