“A Picture is worth a Thousand Words”woodsfords.uk/A-Picture-is-worth-a-Thousand-Words... · 2019. 8. 11. · Title “A Picture is worth a Thousand Words” Author: Peter Woodsford

“A Picture is worth a Thousand Words”

A personal memoir of the Early Days of Computer Graphics

Peter Woodsford, Cambridge Computer Laboratory CAD Group,

1968-75.

'A Picture is Worth a Thousand Words' - P. A. Woodsford, U3AC Summer School 2019

Synopsis

• The Computing Scene ~1967• Mainframes and the emerging mini-computers• Emerging graphics facilities• Cambridge

• The GINO general purpose 3D graphics package• My role• Technical Description• A variety of users

• GINO at the Mintech CAD Centre, Madingley Road

• What came next• GINO-F• Rapid hardware developments, including raster displays• For me, a move to Laser-Scan Ltd., the first company on the Cambridge Science Park

• References


Computing was still dominated by MainframesAn IBM 704 Mainframe (1964)

By Lawrence Livermore National Laboratory, Attribution, https://commons.wikimedia.org/w/index.php?curid=1565787


https://commons.wikimedia.org/w/index.php?curid=1565787

Minicomputers were beginning to appearThe Digital Equipment Corporation (DEC) PDP-7


Early Graphics Capabilities were pen plottersThe Calcomp 565 drum plotter, introduced in 1959, was one of the first computer graphics output devices sold. The computer could control in 0.01 inch increments the rotation of an 11 inch (280 mm) wide drum and the horizontal movement of a pen holder over the drum. The pen was pressed by a spring against paper scrolling across the drum. A solenoid could lift the pen off the paper. This arrangement allowed line drawings to be made under computer control.

https://en.wikipedia.org/wiki/Calcomp_plotter

and a clip of the plotter in action.


https://en.wikipedia.org/wiki/Calcomp

https://en.wikipedia.org/wiki/Plotter

https://en.wikipedia.org/wiki/Computer_graphics

https://en.wikipedia.org/wiki/Computer

https://en.wikipedia.org/wiki/Solenoid

https://en.wikipedia.org/wiki/Calcomp_plotter

https://www.youtube.com/watch?v=qe8jLSiz_vE

In Cambridge, ingenious means were found to produce graphics on EDSAC 2


In 1966, the Titan multi-access computer was launched in CambridgeMulti-access facilities were available to all Computer Laboratory staff and then across the University. Users could input and edit programmes using teletypes, run them and receive the results back directly. A huge step forward over batch computing.

A Calcomp plotter was available as part of the University Computer Service


The University Computer-Aided Design projectCharles Lang led the University CAD project established in 1965.

It received a PDP-7 minicomputer with a 340 Interactive Graphics Display, one of the first in the country. It cost £50,000 (equivalent to £817,000 in 2019).

The picture is of the slightly later PDP-7 at Edinburgh University.

Note the lightpen and the teletype


In 1968 I joined the CAD GroupI had graduated with a Cambridge mathematics degree in 1963 and spent the next four years teaching mathematics and physics at Busoga College, Mwiri in Uganda.

During that time we introduced the School Mathematics Project syllabus and textbooks (adapted for East Africa). The experience of teaching matrices and transformations to 14 year olds was to prove invaluable later.

In 1967 I took the Diploma in Numerical Analysis and Computing back at Cambridge and was then offered a Research Assistant post in the CAD Group.


The School Mathematics Project and the ‘Spotty Books’The East African version of the SMP textbooks had covers with a grid of coloured dots and so were known as the ‘Spotty Books’.

I thought I still had one at home but failed to locate it, so have to make do with this published paper extract.


My First Experience of Computer GraphicsSoftware had been written on the PDP7 to create data structures representing simple pictures and to convert such data structures to display files for the 340 refresh CRT display

As part if my dissertation for the Diploma I wrote macros to create the assembly language to create such data structures, commands for points, lines and subpictures.

Polaroid photos were the standard way at the time to preserve images from the screen.

Maybe this project helped get the post in the CAD Group?!


My First Project was GINO (Graphical INputand Output)• A package to make graphics capabilities available to Fortran

programmers was needed, so users could concentrate on their applications and have the graphics looked after for them

• An initial version had been implemented by various members of the CAD group. This proved the concept but was not readily usable.

• The mandate of our CAD Group was Mechanical Engineering so 3D capabilities were a ‘must’.

• Design Objectives included• Simple tasks should be simple

• General Purpose, with a wide range of capabilities


The Available HardwareFortran programmes ran on the TITAN/ATLAS 2 multi-access computer system

Graphical Output could be sent directly to plotters

Refresh Displays controlled by minicomputers (PDP 7/9, ELLIOTT 905) provided graphical interaction

The minicomputers were connected to TITAN/ATLAS by telephone lines (4800 baud) or a high speed data channel (>20K baud). My roommate Phil Cross was the guru of this data link


Picture Generation and Device Independence

• There were Fortran routines to generate picture parts in 2D and 3D• Points, Lines, Invisible Lines, Circular Arcs

• Users could also define Objects (made up of picture parts or already defined objects) for re-use

• Pictures (made up of picture parts and objects) were sent to the currently selected graphics device (plotter or display).

• A single initiation routine determined the selected graphics device• To change device selection, only the initiation routine had to be changed

• This ‘device independence’ proved a great strength as more and more different graphics devices appeared

• For the refresh displays picture parts could have ‘names’. A lightpen hit on a picture part returned its name – the basic mechanism for interaction


Coordinate Transformation

• GINO provided powerful transformation facilities to generate views of 3D objects

• Implemented by matrix multiplication (back to SMP days, but now I had to learn how to programme these efficiently)

• The order of transformations mattered! (AB does not always equal BA, as every SMP student knows)

• Rudimentary Lawn Sprinkler, arm objects transformed to three positions


Windows and Clipping• Displays and plotters had limited

areas, typically 1024 x 1024• Going outside these areas resulted in

error messages – very discouraging

• Users defined their pictures in their own coordinate system

• GINO clipped the relevant part of the user picture (or the whole) and mapped it on to a user-defined Window in the display space (thus avoiding edge violation errors)


Perspective Views, 3D Clipping and Depth ModulationHomogeneous Coordinates (x, y, z, w) and 4x4 matrices were needed to generate perspective views. This was quite novel at the time

Clipping between two z-planes was used to create sectional views and to support depth modulation. The DEC 340 display allowed lines to have 8 different intensities. GINO used the brightest at the ‘front’ graduating to the faintest at the ‘back’.

This created an illusion of depth.

Many users would have liked ‘Hidden Line Removal’ but this was too complex to be implemented in GINO except for a few special cases.

Car Bonnet (J. Talbot) displayed using depth modulation


Choice of Implementation Language

• The first version of GINO had been written in Fortran – the result was too inefficient to be generally usable

• A new more efficient version could have been written in machine code, but this was ruled out for maintainability and clarity reasons

• SAL – Systems Assembly Language, was chosen. It had many of the readability characteristics of a high level language• IF…THEN…ELSE• FOR <this> DO <that>

• But machine code could be inserted where needed for efficiency

• SAL was created by a Compiler Compiler and so new language constructs could be added• Phil Cross would often oblige with requested new constructs overnight


User Manual• A large part of the User Manual sought to explain the basic concepts,

which were very new at the time• Lots of inputs/critiques by engineers who were not ‘computer literate’

(although that phrase did not exist at the time!)

• People were used to poring over pages of printout – ‘A picture is worth a thousand words’

• And of course there were the detailed descriptions of all the routines

• The last paragraph of the introduction read:


Routines for automatically generating Graphs were very popular• Automatic scaling to

screen/paper size avoided edge violations – an all too common pitfall for users• Edge violations resulted in at best

an unhelpful error message (plotter), at worst a flash and a blank screen (displays)

• Linear and logarithmic scaling

• Annotation, but only basic ‘stick’ characters


Visualisation of Chemical Reactions -‘Computational

Study of the Reaction between CH4 and CH4+’ by David Field et al.


Coordinate Transformation, perspective view of 3D object. The CAD Group lived on Floor 7


Two Application Areas of Great Future Importance• ‘The Nematode Worm Man’

• Plotted huge numbers of cross-sections of the nematode worm

• Was the bane of my life for a while as he was always breaking the system

• He was Sydney Bremer’s research assistant

• 1982 Nobel Prize

• Visit by Consultant who said his principal wanted to find out if Movies could be made using Computer Graphics• MIT, Cambridge UK, Salt Lake City

• We said, ‘Yes, in principle, but….’

• We heard later that his principal said – ‘ OK, just buy lots of hardware’• Was it George Lucas?


https://www.newscientist.com/article/dn2890-geneticists-and-a-tiny-worm-win-nobel-prize/

Jet Engine Nozzle, Courtesy of Dr. J. I. Gill

Defined as Surface patches, Axonometric Projection, note use of Depth Modulation.

Triangulated for Finite Element Analysis. Density proportional to curvature.


Hospital Visualisation, with Hidden Lines removed (special case) – Courtesy of Applied Research of Cambridge


Impact

• A large diversity of users – I just learnt enough of each to be able to advise and support

• Access to the PDP7 and the 340 Display was very limited

• Many users of GINO across the University Computing Service generated enough useful examples to justify acquisition of their own graphics displays• Chemists, Molecular Biologists, Radio Astronomers,…….

• Secondees from Industry to the CAD Group took their experiences back with them.

• Advent of the Ministry of Technology CAD Centre at Madingley Road


1970 – Sabbatical Term at Bell Labs, New Jersey, USABell Labs had developed a Graphical Language – GRIN-2.

It was implemented on a GE mainframe linked to dedicated Graphics Processors, an alternative to the TITAN/ATLAS setup.

GRIN-2 was very strong on 2D graphics, especially for electronic circuit design. The graphics were generated from an underlying data structure, which was also used for electronic analysis purposes.

I implemented an interactive curve design programme and, with some difficulty, a 3D surface patch design programme.

GINO and GRIN-2 had different objectives. Both grappled with the IT limitations of the time.

There were two very interesting projects at Bell Labs at the time – UNIX and the Picturephone.


The ‘MinTech’ CADCentre, MadingleyRoad, 1967 onwardsTitan was the prototype of the Atlas 2 ‘supercomputer’ of the day. The government had one spare Atlas 2 on its hands and Anthony Wedgewood Benn, the then Minister of Technology, took the decision to use it to set up a national CAD Centre in Cambridge. Arthur Llewelyn was appointed the first Director.

Fortunately the decision was taken to use the Cambridge multi-access system from the Computer Laboratory as the operating system.

This meant, inter alia, that GINO could be deployed and used at ‘MinTech’.


A much wider range of users and of graphics equipmentIt was part of my job to facilitate the use of GINO at Mintech. The ‘device-independence’ of GINO really came into play as they acquired every new advance in graphics systems from the Tektronix 611 Storage Tube display (the first low-cost terminal) to the massive Kongsberg Kingmatic drafting system suitable for outputting printed circuit and other precision artwork.

CADC staff could add these new devices themselves, and rapidly suggested or implemented other improvements to GINO.

During the three day week, Corn Exchange Street and Madingley Road were on different powercut regimes, so I cycled from one to the other.


Bottle Design, courtesy of CAD Centre

A solid of revolution, profile designed using Bezier curves and lightpeninteraction

Solid image, produced by rendering software (Martin Newell)


Bank Note Design and the Thomas de la Rue ConnectionOne day Bob Tonks, the Plotter Manager at CADC, told me he had a user, Rosemary Trinder, who was jamming up his Kingmaticflatbed plotter for days on end.

I had then started work on a new project, a High Resolution Laser Display. I offered to try these plots on the Laser Display. The output was a small holdall of paper tapes. They took the best part of an hour to read, but plotted on the Laser Display in about five minutes.

The plot opposite is of a sample later design incorporating Professor Robert Frisch, the first chairman of Laser-Scan Ltd.


Laser-Scan subsequently supplied a Banknote Design system to de la Rue Giori, who sold it around the world.


GINO-F, available across platformsEncouraged by the success of device-independence, CADC decided to implement GINO in Standard Fortran. The result – GINO-F, could be used across all platforms from the largest mainframes to the latest mini-computers.

I undertook a modest consultancy contract advising on this project (nobody seemed to know, or want to know, where the IPR in GINO resided).


CADC marketed GINO-F extensively


What Happened Next – GINO-FIn 1988 Bradley Associates bought the full development and marketing rights in GINO-F from the CADCentre

The successor company still markets and supports the latest versions of GINO-F worldwide: http://gino.co.uk/

GINO-F became one of the top 20 global software packages of its time


http://gino.co.uk/


What Happened Next in the Big Wide WorldMemory got cheaper and cheaper and colour raster displays took over

Much of the functionality pioneered in GINO (3D coordinate transformations, clipping, windows) was implemented in hardware –graphics cards

The WIMP interface (Windows, Icons, Menus, Pointer) developed at XEROX Parc essentially solved the graphical input/interaction problem. You use it, or something like it, today (whether you know it or not!)

High quality scalable text fonts came into everyday use


What Happened Next -Personally

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I Joined Laser-Scan, the first company on the Cambridge Science Park, as Technical Director, then Managing Director and finally Chairman (retiring in 2009)

The company migrated from hardware manufacture to software for digital mapping and security printing.

Nowadays it is called 1Spatial and specialises in geographic information management and ‘Big Data’


References

• ‘The Design and Implementation of the GINO 3D Graphics Software Package’, P. A. Woodsford, Software – Practice and Experience, Vol. 1, 335-365, (1971). John Wiley & Sons Ltd.• Many of the illustrations in this presentation are from this paper

• There is an accessible copy for the purposes of this presentation here.

• GINO – Graphical Input/Output. Third edition. Edited by P. A. Woodsford, University of Cambridge Computer-Aided Design Group, (June 1970)

• AVEVA – Fifty Years of Innovation, (2018)


https://www.researchgate.net/publication/220280274_The_Design_and_Inplementation_of_the_GINO_3D_Graphics_Software_Package

Thank you for your attention

• My email address is [email protected]

• A copy of this presentation will be available at:• http://woodsfords.uk/


mailto:[email protected]

http://woodsfords.uk/

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“A Picture is worth a Thousand Words”woodsfords.uk/A-Picture-is-worth-a-Thousand-Words... · 2019. 8. 11. · Title “A Picture is worth a Thousand Words” Author: Peter Woodsford