spectrum graphics - OpenLibra

Animation is the process that
puts life into computer games,
but has far wider uses. The ability
of a computer to create, move
and display visual information
has only reached the home
market fairly recently,and is
becoming a very popular and interesting
application for users at
all levels.
Computer graphics is a term
that means different things to
different people, but generally
covers images that are com
puter generated, modified,
stored and displayed but need
not necessarily be animated. To
a businessman, 'graphics'
means histograms, graphs and
other methods of presenting
financial information visually; to
a railway signalman the mimic
display showing train moves is a
form of computer graphic; to a
student pilot on an aircraft
simulator the realistic images
are computer generated. Com
puter aided design perhaps involves
the most complicated im
agery of all, think about car
design as an example. A good
deal of computer graphics is
merely static images that can be
displayed when required,
animation is the art of making
those images appear to move in
such a way that the impression
of a lifelike object is created.
Animation is an art that predates
the computer revolution by quite
a long time and its application is
a practised skill. Cartoons are a
much loved example of film
animation and such films have
given pleasure to millions, but
few of these millions have ever
given much thought to the sheer
effort involved in producing
those cartoons. In one second of
film there will be twenty four
frames and each frame is an in
dividual picture showing a stage
in the motion of the animated
object. It doesn't take much
mental arithmetic to work out
how many individual pictures
there are likely to be in a ten
minute cartoon feature.
Cartoons are an example of
drawn animation that uses the
skill of an animator to draw a sequence
of individual pictures
which, when filmed, give the impression
of motion. There are
other techniques of animationmodel,
cutout and rostrum (con
trolled camera) animation are
examples.These techniques are
more suitable to the use of computers
to aid such activity,
drawn animation is more directly
applicable to using computers to
replace manual techniques and
thid is the main topic of discussion
here.
Animators in the film industry
are skilled people and the sue-
32
GRAPHICS
Wise Moves
Michael Spencer shows us some ways of
getting things moving around the
screen.
cess of the work depends on
their grasp of two factors-timing
and realism. Correct timing can
convey the impression of animation
well and that timing ought
to reflect the behaviour in the
real world of the object being
animated. Realism ensures that
the object and its behaviour
reflect the laws of motion and
the presence of gravity. These
techniques have been built up
over many years and it is only
their application in the use of
computers that is new — the
computer screen is only another
medium on which to display images
(it may be called electronic
paper). The computer may also
be a means to an end, com
puters as animators' tools are
having an impact on the film industry.
Remember the Walt
Disney film TRON about a computer
programmer and his battle
against a wayward super computer?
A good deal of that film
was made by using computer
animation and still graphics a
novel approach that created a
stunning impact. Computers
can take the tedium out of the
process of producing images for
animation a single image
can be manipulated to a new
position, size or shape by applying
mathmatical routines. Taken
to an extreme it may be possible
to produce a complete film in a
few years time, and indeed a
Hollywood film company is using
a CRAY super computer to
cope with the fantastic number
of calculations involved in such
processes. This machine made
its debut code cracking in
American for the Government
and has since made contributions
in many other fields.
Animation itself involves
three basic processes
preparation of the image,
manipulation and display. It is
the manipulation that is at the
heart of the technique of anima
tion. The computer offers the
electronic paper for us to exploit
and the characteristics of that
paper determine what sort of
animation is possible. There are
three sorts of graphics that can
be created on most home computers
block, pixel and line
graphics. Block graphics involve
the use of character sized
shapes (see the top row of the
Spectrum keyboard} which may
be used individually or as part of
larger shapes which can be moved
around the screen. The pro
gram in figure one creates such a
shape and moves it around. The
program is reasonably effective
and shows some of the basics of
simple animation. An image
drawn on the screen is erased
and a new image created in a different
place which gives the apperance
of motion. A variation
a very reasonable resolution of
176 by 256 pixels each of
which can be individually set
and tested. In case of a single
pixel being moved around the
screen the technique is similar to
block graphics, the pixel is set
and unset (erased) and moved to
a new position after appropriate
delay. Groups of pixels make up
the high resolution screens that
form the bulk of a computer
games attractions. These
shapes can be animated by dealing
with the individual pixelsthat
make them up. Collision deted-
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