Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sgi!thant@horus.sgi.com
From: thant@horus.sgi.com (Thant Tessman)
Newsgroups: comp.sys.sgi
Subject: Re: Overlay planes
Summary: 96 planes
Message-ID: <40363@sgi.SGI.COM>
Date: 16 Aug 89 16:12:02 GMT
References: <36536@bu-cs.BU.EDU>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 26

In article <36536@bu-cs.BU.EDU>, tjh@bu-cs.BU.EDU (Timothy Hall) writes:
> Real work question:
> 
> I am planning on porting a paint package to our 240 soon.  The package wants
> 8 bitplanes and the Iris 4sight manual tells me the max overlay planes I
> can get is 4.  (I don't need the window manager)  Now somewhere along the
> line I thought I heard the 240 has 96 bitplanes - 64 bits image buffer -
> 24 bit z-buffer and 8 bits of overlay.  So is my memory fading?  If not how
> do I get all 8 overlay planes?
> 
[the question I don't know how to answer deleted]
> 
> -Tim Hall
> Boston University Computer Graphics Lab
> tjh@bu-pub.bu.edu


Four bits are for overlay and four are for window I.D.  That's how the 
machine does arbitrarily shaped and/or overlaping windows in different
modes that can be independently swapped, all without any performance hit.

If you talk about what you need the 8 overlays for, somebody may have a
a better/workable solution.  (What machine had 24 bits of color AND 8 bits
of overlay?)

thant@sgi.com