Re: multisampling control

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Simon Bennett (simonb++at++wormald.com.au)
Tue, 16 Jan 1996 20:57:39 +1100 (EST)


On Mon, 15 Jan 1996, Gene McKenna wrote:
> At 9:15 AM 1/15/96 -0500, Bernard Leclerc wrote:
> >On Jan 12, 12:24pm, Simon Bennett wrote:

> I guess I still don't understand how to turn off multisampling entirely.
> Bernard mentions "multisample(FALSE)" and the Performer Ref. Man mentions
> "mssample(MSS_POINT)" but I can find no detailed information on either.

Try the GL manuals for these two: Volume II Section 15.5.1 onwards

(and of course the man pages! They complement each other)

> The Performer Ref. Man says that on an RE system, setting
> pfAntialias(FAA_ON)
> then "Non-multisample buffers, such as zbsize, stensize are all deallocated."

If you're running Performer on a RE^2 and you've got pfAntiAlias turned on
by one means or another (global GState etc...) *and* if you have
sufficient frame buffer memory (read RM's!) for the resolution etc.. that
you're running at, then Performer will turn on multisampling. If you
*don't* want multi-sampling then you can disable it via (for example)
calling pfAntialias(PFAA_OFF) - look at the code for perfly as an
example... (perfly.c around line 620 1.2 or 1037 2.0).

When you turn anti-aliasing *on* on a RE^2, and you've enough framebuffer
memory to multi-sample, Performer does the right (and convenient) thing
and deallocates the "normal" (i.e. non-multisampled) z and stencil
buffers. That's what your manpage excerpt is talking about.

> I agree with Bernard that you shouldn't need multisampling to do
> zbuffering

You don't. See last message and above.

> but then what does this statement in the Ref. Man mean? Is this

Hopefully I've explained this! There are two possible zbuffers, the
normal "single sample" zbuffer and the "multi-sample" zbuffer. You can
have one, none or both, but they don't "talk" to each other - so most
times if your using one you want to "get back" the framebuffer memory
that the other one is using. Ditto for the stencil buffer.

> Finally, after I test my scene with no multisampling, I'd like to set
> my own multisampling points. The OpenGL guide tells how to do exactly
> this. If I were able to turn off Performer's multisampling,
> should I be able to use the GL commands to do my own sampling?

Dunno if this would be a great idea. I gather you're talking stuff like
msmask? (or it's OpenGL equivalent??) It *might* mess with Performer's
fade LOD effects, but I couldn't say and I've never tried it.

Out of interest, why do you want to set your own multisampling points?

+----------------------------------------------------------------------------+
  Simon Bennett simonb++at++wormald.com.au
  Wormald Technology Advanced Systems Engineering Ph: +61 2 9981 0611 (x512)

          Meeting - an event where you take minutes and waste hours.


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