Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Tue, 8 Oct 1996 17:38:07 +0100
these two issues seem to get raised together every time with IMPACT.
Since you mentioned the amazing new O2, there's no danger of you using RM6
levels of framebuffer memory since the O2 won't Multisample but you can
still can line antialias or accumulate.
O2 will use 32 bit or 16 bit pixels and you can select 16 or 32 bit Z.
If you don't have a truckload of RAM you don't have to loose what you've
got to the framebuffer. O2 will dither 16bit rgba when that's what you
need.
At the risk of a little confusion confusion you'll be glad to hear that
O2 supports the much lamented RGBA 1555 format which everyone would like
on IMPACT.
Cheers,
Angus.
On Oct 8, 12:48am, Dennis Pierce wrote:
> Subject: Re: Texturing on MaxImpact
> Hello folks!
>
> I've seen a seemingly straight-forward question take at least
> one fork, so here's an attempt to rejoin the paths.
>
> 1. The default number of bits per texel used on the RE and IMPACT are
> DIFFERENT. This is not only based on the amount of TRAM installed,
> either none, 1 MB or 4 MB, but also on just what has been "selected"
> as the default by whoever wrote what demo you're viewing. In
> the "Performer Town" demo refered to initially, the fewer number
> of bits allocated to each chromatic band in the RGB texel does
> lend itself to "banding" in the textured road. 16-bits for RE
> vs. 12-bits for IMPACT means that 5-bits R is now compressed to
> one-half the visual range, namely 4-bits. Similarly for G and B.
>
> 2. Ever since the PI, SGI's desktop machines (of which the IMPACT
> is one) have used 12-bit frame buffers. Deskside and rack machines
> have used 24-bit frame buffers. The 12-bit frame buffer leads to
> what some have correctly called dithering. Remember "virtual 24"?
> That was the original purple Indigo slogan and still lives. O2
> does not follow this trend, but remember one RM6 has 160 MB of
> frame buffer RAM, so you may approach the 1 GB main memory limit
> by the time you configure a great color space, throw in the OS,
> and tuck in your app. :^)
>
> So, there are two issues which are distinct but seem to be becoming
> blurred in this thread.
>
> Hope this helps and good luck to all!
>
> bye.
>
> --
> Dennis Pierce
> POB 321206 CCB FL 32932
> 407.783.7656
> dpierce++at++digial.net
> http://www.digital.net/~dpierce
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>-- End of excerpt from Dennis Pierce
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