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Intro | Part
I | Part II | Part
III | Part IV | Part
V | Part VI | Part
VII | Downloads
Introduction
This tutorial is an introduction
to the use of LightWave 3D's expressions to rig
mechanical systems. I assume very little mathematical
or expression knowledge, but I do assume you
have a little working knowledge of the rest of
LightWave®. The tutorial uses an imaginary
pedal powered helicopter to illustrate the use
of expressions in a few simple contexts. Since
the emphasis of this tutorial is on the use of
expressions to rig mechanical systems, I have
provided all the objects and scene file (I will
have little to say about the modelling of the
Copter) – see the download page.
The tutorial is broken into
several parts. At the beginning of each part
the complete scene file up to that stage is provided.
Thus you can skip any part, load the scene file
at the beginning of that part and do only that
part of the tutorial.
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Part
I: A general introduction LightWave® Expressions.
This
part is somewhat brief (and not intended
as a replacement to the manual). You
can skim through this part at first reading
and return later as needs be.
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Part
II: Null rigging of the model.
The
use of Nulls is very important in any
mechanical rig, thus in this part we
load the objects and parent them to appropriate
Nulls.
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Part
III: The pedals.
This
Copter is pedal powered. The rotation
of the pedal gear will be under the animators
control with keyframes, but, using expressions,
we will make sure the pedals automatically
point in the same direction (irrespective
of the rotation of the gear).
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Part
IV: The chain.
The
rotation of the chain connecting the
pedals to the rotor can be set up in
several ways. We will use the morph method
with an expression controlling the morph
percentage to ensure the chain rotation
is synchronised to the gear rotation.
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Part
V: Rotor, counter rotor and associated
gears.
In
this part we set up expressions to link
the rotation of the rotor to the pedals
and chain.
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Part
VI: Rotor Droop.
To
add some realism to the motion we use
use an EndoMorph rotor object and expressions
to control the "droop" of the
Copter rotor blades. The new ingredient
in this part (cf. part IV) is that we
want the droop to be controlled by the
speed of rotation (not the amount of
rotation).
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Part
VII: The Wheels.
Finally,
we add rotation to the wheels. In this
part conditional (or control) expressions
are introduced to ensure the wheels only
rotate when the Copter is on the ground,
but respond to keyframing when the Copter
is off the ground.
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I hope this
tutorial flattens the learning curve a little.
Drop me an email (r.brak@richardbrak.net)
if you have any queries or comments.
Cheers,
Richard Brak.
PS. Almost
all the images can be clicked on for higher resolution
versions (in a separate window – which
closes automatically, or, if you prefer, clicking
on the target,  ,
which will open the image in the same window).
All contents copyright © 2001 Richard
Brak unless otherwise specified. All the
objects and scenes are copyright. They may
only be used as part of this tutorial and for
no other purpose whatsoever unless my permission
is first obtained.
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