Re: Texturing on MaxImpact

New Message Reply Date view Thread view Subject view Author view

Guy Russell (guyr++at++thoth.engr.sgi.com)
Tue, 8 Oct 1996 10:54:48 -0700

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.

The jist of this is correct (ie 4 bits vs 5 bits of resolution for each color
component), however the Impact is also using 16 bits on 4 component textures.
See Rob Jenkins previous post on available texture formats on Impact.

>
> 2. Ever since the PI, SGI's desktop machines (of which the IMPACT
> is one) have used 12-bit frame buffers.

This is not true for Impact. The Impact has a configurable framebuffer, which
most apps use in 32 bit double buffered mode with a 24 bit Z buffer.

> 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.
>

Guy

-- 
                    Guy Russell
Vis Sim Applied Engineering    	Silicon Graphics Inc.
Email:guyr++at++engr.sgi.com          2011 N. Shoreline Blvd. M/S 3L-916
Phone:(415)933-6113              Mountain View CA 94043
=======================================================================
List Archives, FAQ, FTP:  http://www.sgi.com/Technology/Performer/
            Submissions:  info-performer++at++sgi.com
        Admin. requests:  info-performer-request++at++sgi.com

New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:53:44 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.