How do you get a giant hot air balloon to float past Blackpool
Tower at the right time or hover over St Michael’s Mount at the right
Simple. Create the entire scene using the most advanced computer
visualisation equipment available.
This is how the post-production house, SVC, produced the latest BBC
The balloon itself was not an original concept - it was used for earlier
idents that were developed through Lambie-Nairn. However, the fact that
the balloon would now be computer-generated marked a breakthrough.
The balloon and the location shots needed to be filmed separately. And
as the balloon was not going to be on location, it was necessary to work
out before the shoot exactly which footage the camera crew would need to
Once a location had been chosen, the first step was to scan a copy of an
Ordinance Survey map of the area on to a computer. This was done in 3D
and exactly to scale, enabling SVC to plan and execute the ideal camera
shot without leaving the office.
Lambie-Nairn provided a still of the balloon in situ which was also
scanned on to the system.
With the map and balloon on screen, SVC could try out different camera
angles, simulate windspeed and weather conditions as well as input the
dimensions of any obstacles like rocks or buildings. This was done so
that the picture on screen was an exact replica of the geography of the
location site and scale of the balloon.
The crew then used this scan to pin-point where the camera should be
filming, what path it should follow and at what speed it should
If the camera was placed too far in the distance, for example, the
foreground would swing past too rapidly.
The director, Jason Keeley, and the animation director, Phil Hurrell,
planned the camera moves in 3D using a program called Softimage Android,
and all the data was saved to a floppy disk. This stage was completed in
just one day in the comfort of SVC’s animation suite.
The data was then transferred to a motion-control camera. The software
would not accept any moves that the camera would not physically be able
to reproduce later on location.
The same processes had to be applied to birds and the reflection of the
balloon on a lake in one of the executions.
As a mark of how seamless the finished work was, the BBC was unable to
pick out the one computer-generated ident from a selection of five that
it was shown.
One of the biggest problems facing the crew was getting the lighting of
the balloon to match that of the location sites. It had to consider not
just the effect of sunlight shining through the balloon but also the
strength of it bouncing off the balloon.
Tom Horton, the head of visual effects at SVC, said: ’The biggest
problem with using computer generation is that you have to be very
specific about everything. If something doesn’t look exact, people will
pick up on it very quickly.’
The obvious advantage, on the other hand, was that the crew had complete
control over the composition of the shots and were able to guarantee
that the work would be finished to deadline.