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From: crum@utah-cs.UUCP
Newsgroups: comp.graphics,comp.periphs
Subject: Re: Fancy Frame Buffers ?
Message-ID: <4401@utah-cs.UUCP>
Date: Tue, 24-Mar-87 14:23:59 EST
Article-I.D.: utah-cs.4401
Posted: Tue Mar 24 14:23:59 1987
Date-Received: Thu, 26-Mar-87 06:32:37 EST
References: <615@rna.UUCP>
Reply-To: crum@utah-cs.UUCP (Gary L. Crum)
Organization: University of Utah CS Dept
Lines: 48
Keywords: anti-aliasing PS390 shadowfax
Xref: utgpu comp.graphics:407 comp.periphs:293
Summary: The E&S PS390 does anti-aliasing in hardware.

In article <615@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes:
>objects, would be difficult. Question: are there any machines that do
>anti-aliasing on the fly ?

The Evans and SutherLand "Shadowfax" project has developed a chipset that
includes anti-aliased line drawing capability.  The new E&S PS 390
"workstation" will have this capability (in addition to the interactive 3D
transformation and depth-queueing that E&S PS systems are known for).  The
PS 390 will be a raster system, whereas other E&S PS systems use calligraphic
technology.

I saw the Shadowfax chipset in action last Wednesday after an ACM talk by one
of the project engineers, Scott R. Nelson.  The testbed that I saw consisted
of 56 1024x768 bit planes and the custom chips on cards plugged into a DEC
MicroVAX.  The test software demonstrated perspective views of color
wireframe images being manipulated interactively.  The test software allowed
one side of the image to be rendered with anti-aliased lines while the other
was left without anti-aliasing.  Actually I saw two testbed systems, one
controlled by a MicroVAX running Ultrix, the other controlled by a MicroVAX
running VMS.

I was told that the Shadowfax chip that draws into raster memory can support
a resolution of 2048x2048.  The chipset uses 32-bit fixed point representation
to maintain the x, y, z, and w coordinates of line endpoints through most of
its hardware pipeline, just as the PS 350 does.  The current Shadowfax chipset
does not have the capability of anti-aliasing polygon edges, nor can it
manipulate curves in hardware without using some polyline approximation of
those curves.

I don't really like to discuss marketing considerations like cost, but I think
that it was mentioned that the meeting that a base PS 390 system should cost
somewhere around $40K.

I'm not sure if Scott reads this newsgroup, but I know that E&S is on the net.
Perhaps someone there could correct anything misleading that I have said here,
and give us some some PS 390 performance figures (which may not really mean
much).

Do any of you know if other manufacturers are working on CAD systems that will
do fast anti-aliasing?  I suppose that the technology used in broadcast video
engineering could also be of interest here (Bausch?).

Bravo, E&S...  You are leading CAD in some very interesting directions.

Gary L. Crum
University of Utah Computer Science Department
arpa:  crum@cs.utah.edu
uucp:  ...{seismo,ut-sally,devax,ihnp4 (among others)}!utah-cs!crum