From: Angus Dorbie (dorbie++at++sgi.com)
Date: 04/17/2000 11:10:13
The actual downloading to graphics is done in the draw but Performer
supports the concept of applying graphics methods in the upstream cull
process, where the effect is effectively queued in a display list and
happens next frame in the draw process. In the case of clip mapping this
is a fairly complex procedure where what's internally called an
incremental state change is implemented. The calculations require a
multistage queue where downloads are prioritized by level and distance
and finally the actual achievable subloads are timed and queued using an
estimated download tally based on previously benchmarked results so that
the cull process can accurately control the subload times to meet the
requirements of the DTR timing mechanism. These subloads then happen in
the draw process and take the predicted time to accomplish. So,
conceptually it's reasonable to say the downloads are applied in the
cull as are many other state changes in Performer, but the real graphics
work gets done later in the draw process.
Cheers,Angus.
christopher.g.dorosky++at++lmco.com wrote:
>
> In the 1998 version of the IRIS Performer Programming Guide, on page 339, it
> says:
> "A pfMPClipTexture allows you to : .... Automatically perfrom the necessary
> texture downloading (applying) in the CULL process"
>
> I thought that texture downloading to TRAM was only done in the draw.
>
> Does downloading mean something different here, does the MPClipTexture have
> a special exception to this rule, or does the rule not apply at all?
>
> Or more simply, is it a misprint?
>
> Thanks,
>
> Chris
>
> Christopher Dorosky
> Senior Electronic Systems Engineer - Real Time Simulation
> Lockheed Martin Missiles and Fire Control - Dallas
> christopher.g.dorosky++at++lmco.com
> 972-603-2349
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