Amiga Computing - Commodore Is Awesome

GRAPHICS
nyone interested in 3D modelling has,
at some point, seen a model so well
made it makes them stop and admire
the creator's handiwork. Whether it be
dinosaurs, animated human faces, or cars with
smooth, flowing lines, there are plenty of examples
around that make you think 'how did they
do Mar
Often, the answer is that they used a 3D digitiser
to 'scan' a physical object and import its
vital statistics to a ray tracing package, where
the model is tidied up before textures and other
effects are added. Indeed, much of the drudge
work in modelling can be done by electronic
sidekicks if you have the sort of production budgets
enjoyed by Industnal Light and Magic.
In high-end digitisers used by movie companies,
a scanning laser beam builds up a picture
of an object's surface in minute detail before
passing the data to a Silicon Graphics machine
for interpretation. The 3D artist can build a
model in plastic or any other substance, or have
it built by the traditional model makers who
brought us the Star Wars designs, then digitise
it to cut out most of the time-consuming job of
translating the model to computer graphics.
PRICE DROP
For a long time now, small companies and
enthusiasts have been unable to use this sort of
technology, but a growing number of American
manufacturers are releasing smaller, less
expensive digitisers which are now coming
down in price - enough for them to be a realistic
option. One such unit is the Immersion
Personal Digitiser which, though still not cheap,
is a powerful tool for any modeller.
Laser scanning would be tar too expensive,
so the personal digitiser makes use of a jointed
arm (much like a robot arm) with a stylus on the
end. This sits on a bread-board-sized base and
is connected to the Amiga via a control box and
serial cable.
Build quality is as good as you'd expect from
a device costing this much. The arm itself is
made of tough, thick plastic with a solid brass
stylus. and the base board is half an inch thick
with rubber feet to stop it sliding around. To
avoid any plug difficulties on either side of the
Atlantic, the control box uses a standard kettle
lead connection, and all necessary cabling
Eand for 'lour bum
Why not just use splines, or the Forms editor in
Imagine? I mean, it's not easy to create organic
shapes, but it can be done. Why spend money on a
digitiser? Apart from obvious benefits in terms of cutting
design and modelling time, 3D digitisers make it
much easier to create a complete model with one continuous
skin. Until Amiga packages utilise the 'smart
skin' techniques found in some Silicon Graphics software,
even fairly simple objects such as a human head
are difficult to produce without bolting two or more
objects together,
Three rough models
created using the
dig/tiger. Note tha t the
human face uses more
5amplos then the other
two, and is therefore
much more eccurate
1•
(including a custom serial cable) is supplied_
The units Vedisketch software is installed
in no time and uses ARexx macros to enable
the digitiser to be controlled directly from
Lightwave's Modeller. There are several con-
trol macros, but the most important - Get
Point - simply passes a position request to
the digitiser's control unit which replies with a
three dimensional co-ordinate. A point is then
created on screen to correspond to the arm's
position when the macro was invoked.
Hardly any delay is involved in the process.
so digitising a long series of points is a simple
matter of moving the stylus to a new location
with one hand and hitting the relevant function
key with the other. The manual suggests
using F10 for the Get Points macro, but you
can set this system up any way you like
Several macros are supplied to ensure
agreement between the arm and Lightwave's
internal 3D world. Set Origin, for example, can
be used to select any point within the arm's
reach and treat that point as Modellers equivalent
of co-ordinate 0,0,0. and the Set
Orientation macro ensures that your digitising
table is oriented in the same way as the
N
the Wjoin
will usually show, and there's nothing more
realism-killing I
than a dirty great line where, for example,
M the shoulder joins the arm. Putting bones Into an
object N like this will produce decent animated effects,
but
i
with one continuous object the effect is far more Using tmagine'a Forms e ditor So cre a te orga nic sha pe s is
convincing.
one a nswe r, but it ca n be a ve ry time-consuming proce ss
V
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Amiga Computing
MAY 1995
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Even relatively sample shapes, like this pipe
bowl, cart be digitised lamter than you could
model them from scratch
Modeller environment. The latter becom
very important because you have an °tail
which is too big or awkward to digitise in o
piece. By creating a simple triangle
Modeller and aligning it with another that y
create using the digitiser, users can arm
that the centre of the digitiser's universe
always in the same Lightwave position.
With this common frame of reference,
is much easier to ensure that two parts al
larger object can be glued together agi
once they've been digitised.
I say much easier, but the process still is
what you'd call a walk in the park. Probal
the biggest limitation of digitisers such as II
one is that they have problems with large
oddly-shaped subjects.
At full stretch, the tip of Me stylus will rea
about 55cm from the base of the arm. t
when you have to loop the arm up and ON
an object, this reach comes down to atx
3
1 For objects such as a thigh bone (uSeC
3one
of the pre-supplied examples), this me
cdigitising
in two or more sections and
rresulting
hassles when the hnished modo
a glued together in Lightwave.
o For smaller objects, the arm is easily et
r ble of digitising a complete object. anc
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