syracuse robin forrest october 2015 comments which fleshed out the presentation have been added to...

Syracuse

Robin Forrest

October 2015Comments which fleshed out the presentation have been added to the slides

All Thatand

Rich Riesenfeldfrom Graduate Student to Utah Professor

Some history

The early history of CAD is largely

undocumented: there were no journals,

research was reported in Technical Memos,

and a great deal of work was carried out by

industry with little being revealed to an

external audience. Defense funding also played an important rôle.

M.I.T.

Sketchpad, Ivan Sutherland

with Elaine Cohen at the 1984 Steven Anson Coons Award presentation.

M.I.T.

TX-2 and display, Lincoln Labs.

Tim Johnson demonstrating Sketchpad-3

M.I.T.

Computer Aided Design Group, 1960’s

Ross, Coons and Ward

funded by the US Air Force

Doug Ross was the developer of the APT part-programming language

M.I.T.

Computer Aided Design Group, 1960’s

Ross, Coons and Ward

Steve Coons

M.I.T.

Project Mac, 545 Technology Square

the building on the right, off to the east of the MIT Campus, housed IBM, the CIA, the AI Lab and the AED Group as well as the Project MAC CTSS machines

MAC stands for Multi-Access Computer or Machine-Aided Cognition

M.I.T.

IBM 7094 running CTSS

Kludge display

Charles Lang operates the kludge satellite display and Doug Ross explains

M.I.T.

Kludge display

peripherals include joystick, light pen and button box

M.I.T.

AED (Algol Extended for Design

or

Augmented Engineering Design)

Doug Ross

M.I.T. 1964

Ross: AED and data structures

Lang: 7094-Kludge link

Coons: curves and surfaces

in the 1960’s computer graphics researchers wrote papers on data structures as there was a need for more complex structures than arrays, lists and trees

M.I.T.

Charles Lang

Cambridge 1965

Computer-Aided Design Group,

Engineering Department (Welbourn)

and Mathematical Laboratory (Wilkes)

Welbourn had heard about Sketchpad and Wilkes had visited MIT and seen both CTSS and Sketchpad. They decided to form a CAD Group, 50 years ago.

Cambridge 1965

Titan (Atlas-2), time-sharing operating system

DEC PDP-7, 8K 18 bit words and 340 display

(£50,000 in 1965)

Additional 32K memory (~64K bytes)

1965 catalog price $100,000

graphics in the mid 60’s was a rich man’s game but Wilkes somehow

had £50,000 to spend at his own discretion

Cambridge 1965

Gray: data structuresLang: Titan-PDP-7 linkForrest: curves and surfaces

the original members of the group, November 1965Lang returned to the UK from MIT

on the screen, designing a bicubic patch in November 1966note MIT design joystick

M.I.T. Summer 1967

Robin Forrest at M.I.T. Project Mac

to work with Coons

(Martin Richards from Cambridge was at Harvard that summer, developing

the systems programming language BCPL which was used by Xerox

PARC for the Alto work stations and inspired Bell Labs to develop first A

then B then C)

M.I.T. Summer 1967

Coons on sabbatical at Harvard

working with Ivan Sutherland

I would commute to Harvard weekly, spending a couple of hours with Steve

and Ivan and then spending the rest of the day with Bob Sproull, Danny

Cohen and Ted Lee

General Motors 1969

Bill Gordon

Mathematics Department

General Motors Research Labs.after completing my Ph.D. thesis in August 1968, I toured

aerospace and automobile companies in the US before and after the March 1969 Computer Graphics Conference at the University of Illinois

General Motors and Bézier 1969

“The crazy way Renault design curves”

I was given a demonstration of the Renault technique: points were dotted around an IBM 2250 display (a clumsy display costing $250,000) and a curve appeared anchored to the first and last points but not interpolating the other points which could be moved to distort the curve - the polygon was not drawn

Bézier had presented a paper earlier in 1969 at a Society of Automotive Engineers meeting in Detroit

Bézier 1969

the following slides illustrate the notation and

formulation as published by Bézier up to the mid 1970’s

V denotes vertices, P denotes points on the curve and

a denotes coefficients.

a0=V0

ai =Vi −Vi−1,1 ≤i ≤nP 0( )=a0 =V0

P 1( )=Vn = aii=0

n

∑

Bézier 1969

P t( ) =a0

+ iai=1

n

∑ nif t( )

Bézier 1969

nif =

−−t( )i

i −1( )!•d i−1Φn t( )dti−1

Bézier 1969

Φ n t( )=1 − 1 − t( )n

t

Bézier 1969

P t( ) = Vii=0

n

∑n

i

⎛

⎝ ⎜ ⎞

⎠ ⎟ ti 1 − t( )n− i

Cambridge and Bézier 1969

I re-cast Bézier’s formulation in terms of polygon vertices rather than polygon sides, revealing he was using

Bernstein polynomialsthis explained the variation-diminishing properties of Bézier’s curves

Summer 1970, Rich sent by Steve Coonsfrom Syracuse University to work withthe Computer-Aided Design Group

Coons moved from MIT to Syracuse around the beginning of 1970, I think

the CAD Group was an eclectic bunch, including visitors from industry - aDutch visitor said we had our heads in the clouds and our feet on theGroundwork in progress included develoment of Bézier’s method and preliminarywork on a B-rep solid modelling system

Cambridge and Rich

Spring Semester Bill Gordon on sabbatical

from GM to work with Coons

Syracuse 1971

Observing that Bernstein polynomials

are a special case of B-splines,

he suggests the use of B-splines for CAD

as a thesis topic for Rich

Syracuse 1971

Fall Semester 1971-2, Robin Forrest

on leave from Cambridge to work with Coons

the original intention was to work with both Coons and Gordon, but Gordon

had decided to return to Detroit earlier than planned

Syracuse 1971-2

Tasked with encouraging Rich

who was under pressure to produce a thesis

Syracuse 1971-2

de Boor and Cox B-spline papers appear

de Boor’s paper was a Technical Report from the UA Army-sponsored Mathematics Research Center in Madison, Wisconsin and Cox’s paper was a Technical Report from the National Physical Laboratory near London. Both were later published as journal papers, but early distribution to interested parties was crucial

the de Boor Cox algorithm was the first numerically stable and efficient algorithm for computing B-splines

Syracuse 1971-2

Syracuse 1971-2

Rich dreaming of B-splines

Syracuse 1971-2

…in his palatial residence…

Syracuse 1971-2

The power behind the throne

I first met Elaine at Syracuse although I was aware whilst Rich was at Cambridge the previous year that his progress was being followed from afar and not only by Steve Coons

Rich and Elaine argued about the limit case of the closed B-spline when the degree tends to infinity. They agreed that in the limit the curve reduced to a point, but not necessarily a circular point. Steve Coons asked “what else could it be”, and as a fellow mechanical engineer I sided with Steve

Syracuse 1972

Thesis complete but where to go next?

Conspiracy

Where Rich should go is debated

– fortunately Rich makes the right decision

Steve Coons, Bert Herzog and I had correspondence about this and tried to influence the outcome, most probably unbeknownst to Rich (apologies are due!)

Utah!

Dave Evans and Ivan Sutherland

Utah!

The rest is history…

a few months after arriving in Salt Lake City, Rich wrote that he and Elaine had decided that the limit closed B-spline curve was an elliptical point - sometimes I don’t understand mathematicians!