Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!purdue!iuvax!watmath!watcgl!dmmartindale
From: dmmartindale@watcgl.waterloo.edu (Dave Martindale)
Newsgroups: comp.graphics
Subject: Request for comments on Pixar and TAAC
Keywords: Pixar, TAAC, framebuffer
Message-ID: <9400@watcgl.waterloo.edu>
Date: 26 Apr 89 17:30:02 GMT
Reply-To: dmmartindale@watcgl.waterloo.edu (Dave Martindale)
Organization: Imax Systems Corporation
Lines: 90

I will soon be doing some work with very high resolution colour images
(4000x3000 pixels and more) and need to buy hardware capable of
processing and displaying at least portions of such images.

The only suitable hardware I know of at the moment is the Pixar Image
Computer, the Pixar II, and the Transcept/Sun TAAC-1 board.  If anyone
has used one or more of these and has any comments about them, I'd
really appreciate hearing from you.  I've already read the manual set
for both Pixar and Taac, so I know what the hardware looks like - I'm
more interested in the sort of knowledge that comes from real
experience with using something.

Pointers to other hardware meeting the requirements are also very
welcome.  I'll summarize the replies.

My requirements:

	Since I'll be working with such large images, I want a
	horizontal resolution of at least 1024, to minimize the number
	of pieces I have to cut the full images into.  512 or 640 just
	isn't acceptable; more than 1024 would be nice.

	Some images will ultimately end up on film.  In order to avoid
	quantization problems and the Mach bands created by them, the
	system needs the ability to work with pixels that have 11-12
	significant bits per colour component at any point where
	arithmetic is being done on components.  8 bits just isn't good
	enough for computations.

	Because of the non-linear response of a CRT, it is not
	necessary to have 12 bits per component going to the video DACs
	in the frame buffer - 8 seems sufficient for practical
	purposes.  Less than 8 is not acceptable.

	The hardware should also have considerable computational
	horsepower so it can do pixel-oriented operations on large
	images in reasonable time (Imagine doing a 5x5 convolution on a
	4000x3000 image).

What I know so far about the Pixar Image Computer (hereafter called
Pixar I), Pixar II, and TAAC:

	The Pixar I is the only machine that will allow panning across
	a 4000x3000 image in memory, even in theory.  (Can you get more
	than 48 Mb of memory on a Pixar I now?)  The Pixar II frame
	buffer controller is integrated with a memory board, so the
	largest displayable image is 2048x1024 without copying data
	from off-screen memory.  The TAAC is limited to 1024x2048, with
	no possibility of adding extra memory.

	Both Pixars store 11 significant bits per component, so you can
	directly view intermediate results when applying a series of
	image-processing steps to an image - this is great for anything
	interactive.  The TAAC is 8-bit oriented - you can do many
	operations on 16-bit components, but you have to transform your
	12- or 16-bit intermediate results into an 8-bit second image
	to display it.  When working with components wider than 8 bits,
	the TAAC effectively has half the memory of the Pixar II and
	1/4 that of the Pixar I.  This will make interactive
	manipulation of images on the TAAC a pain.

	The Pixars seem harder to program at a low level - they are
	SIMD machines, and pipeline delays are visible to Chap
	programs.  Image memory can't be addressed directly; pixels
	must be brought into the scratchpad for use.  There is no
	floating point.  Most arithmetic is 16-bit.

	The TAAC is SISD (for each processor), with no pipelining.
	Image memory can be randomly accessed by the processors, and
	used for simple 32-bit word storage as well as pixels.
	Arithmetic is 32-bit, and a floating point unit is available.

	The Pixar has a multi-layer set of software libraries, and you
	can do a lot without ever writing code that runs on the Chap.
	However, it will take quite a while to become familiar enough
	with the hundreds of routines to select the "best" way of doing
	something.  The TAAC software structure is much simpler.

	The TAAC fits in 3 slots on a Sun, requiring no separate power,
	cooling, or space.  The Pixar II is a separate standalone box.
	The Pixar I mounts in a rack.

Anything that you can add to the information above would be appreciated.
Subjective impressions ("It took me 3 months to figure out the video
registers") are particularly interesting.

	Dave Martindale

	watmath!watcgl!dmmartindale
	dmmartindale@math.waterloo.edu