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Further reading □ OverviewArrival 1970Early 1971Summer 19711972197319741975Addressing □ PDP15 Manuals □ ReferenceFortranMacro15MonitorInstruction ListDOS-15 Ref Card □ VT15 Manuals □ ProgrammingMaintenance
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ACLTechnologyDEC PDP15 :: DEC PDP15
ACLTechnologyDEC PDP15 :: DEC PDP15
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Further reading

Overview
Arrival 1970
Early 1971
Summer 1971
1972
1973
1974
1975
Addressing
PDP15 Manuals
Reference
Fortran
Macro15
Monitor
Instruction List
DOS-15 Ref Card
VT15 Manuals
Programming
Maintenance

PDP15 System Development: Mid 1971

Staffing

The summer of 1971 saw the main group involved with the PDP15 (Bob Hopgood, Graham England, Julian Gallop and Paul Nelson) augmented by Professor Judah Schwartz from MIT and David Ralphs, a Brunel sandwich student. Quite a bit of time was spent organising the Computer Animation Symposium during the summer.

CAMP

CAMP and later CAMPER were moved to the PDP15 by David Ralphs. The small size of the PDP15 main memory and the poor quality of the Fortran compiler made this more difficult than it should have been. The program had to be broken into a set of chains that called each other. Some more memory had been ordered for the PDP15 and when that arrived the aim was to have the ability to watch the animations prior to production on the SC4020 and thus speed up development time.

SPROGS

Work started on the design of the new software system, SPROGS: SC4020 PDP15 Rapid Output of Graphics System, that was to replace GROATS and the existing Fortran system. The aim was an interactive development system on the PDP15 coupled to the ICL 1906A where computational intensive processing would take place and the batch production of output tapes for the SC4020. The system borrowed ideas from most of the existing graphics packages and cured the faults that had been noticed in the Atlas systems.

Complete System

At the end of July, the PDP15 was moved to the new ICL 1906A machine room. The extra 16K words of memory arrived (making 32K) and the full screen vector drawing hardware for the VT15. The accuracy of the vector drawing was not good initially and it took several months before the equipment was eventually accepted. There was also cross talk between the I/O devices and the display. Every time a magnetic tape record was written, the display flickered.

The addition of a 256K word disc was a major advance. While DEC tape was still the main user storage medium, it did mean that scratch space, the monitor program and buffering I/O to disc were all now possible.

Tomorrow's World

In July, 1971, the BBC approached the Group for help in producing the BBC's Tomorrow's World programme entitled Computers and the Animation Industry. The aim was to show how a computer could be used to aid the professional animator in the design stage of his work.

Julian Gallop showed how the D-MAC pencil follower and display could be used to check out an animation sequence. Julian captured a number of drawings of a cat and a bloodhound on a motorbike using the D-MAC and these were stored on DEC tape. There were four positions of the bloodhound (B1 to B4) and six of the cat (C1 to C6). A movie cycle was created that could either be displayed on the VT15 or captured on film using the SC4020. The 24-frame sequence was B1C1, B1C2, B2C3, B2C4, B3C5, B3C6, B4C1, B4C2, B1C3, B1C4, B2C5, B2C6,B3C1, B3C2, B4C3, B4C4, B1C5, B1C6, B2C1, B2C2, B3C3, B3C4, B4C5, B4C6. It was possible to display it back at different rates on the VT15. This sequence was shown in the Tomorrow's World programme. Due to the lack of the random vector hardware at the time, the system only managed to draw at 3 frames a second!

Graham England produced the same sequence on the SC4020 and using some of the GROATS in-betweening functions, various effects involving the cat and dog were produced. Some of these were shown in the programme.

The BBC were also interested in showing how the computer could be used to generate in-between frames automatically. Bob Hopgood took a walk sequence from Preston Blair's book and digitised the major frames of the man walking and generated the in-between frames using GROATS.

The Tomorrow's World programme was televised in September 1971.

A re-creation of Bob Hopgood's Man Walking Sequence using SVG
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