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Tutorial
Tumbling Objects
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Lightwave Tutorial – Object Tumble.
This is a short simple tutorial, but it does assume a basic working
knowledge of Lightwave, in particular it assumes knowledge of key
frames, nulls, and parenting. If these are new to you, it would be
handy to check the manual before you get started!
Sometimes a really nice way to show off your 3d object is to have it
gently tumble in the centre of the screen, so you get to see it from
different angles. When I first tried to do this, it was surprisingly
tricky to get it looking good.
At the risk of showing my age, what I had in mind was something like
the old computer game "Elite", an elegant gentle roll, smoothly sowing
rom every angle.
The simple approach I first tried was to get the object, and set a
steady increasing rotation on heading, pitch and bank. But it seemed to
get stuck for periods, or do odd twirls, it was very uneven, and also
very difficult to adjust. Thinking about it, when part of the object is
pointing up near the pole, (to use a geograpical analogy), a large
increase to rotation around the equator in latitude will only produce a
small movement.
After a bit of thought I came up with a better method.
The trick is to make each of the three axes independent, and this is done by use of parented nulls.
So here we go.
Getting Started:
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Start with a completely clear scene, and add three nulls.
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Name these nulls: null-roll-heading, null-roll-pitch, and null-roll-bank.
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Set the end frame on the scene to 750, or something like that –
the exact number is not important, but this should work well.I chose it because that's 30 seconds of animation.
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Go to the end frame, and select null-roll-heading. Set the heading to 340.
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Select the null-roll-pitch. Set the pitch to 250.
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Select the null-roll-bank. Set the bank to 90.
Click for a larger version.
- To avoid mistakes I recommend that you disable the other rotation
channels, by clicking on the H, P or B buttons as approprioate.
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You can choose different numbers if you like – the exact values
are not important, but make sure they are not the same. If you make
them factors of each other, e.g. 100, 200, 300 then the patterns will
repeat eventually.
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Now we need to make sure that the rolling will continue for as long as
we want, so go to the graph editor, and select each of the values we
just entered in turn. Set the after behaviour to ‘repeat
offset’, so they will carry on turning.
- Increase your end of scene value to 1500 or more to check.
Click for a larger version.
Parenting.
As we all know, good parenting is an important skill, and in this case
it is essential for the effect to work. The nulls must be parented to
each other, so that the motions add up, and we get movement in every
dimension.
So, take the null-roll-pitch, go to ‘motion options’ and set the parent object to null-roll-heading.
Next take the null-roll-bank object and parent it to null-roll-pitch,
so we have a chain of parents, from heading to pitch to bank. (The
exact order again does not matter, but for now follow me).
Here's a grab of the scematic view of the scene, click for a large version:
If you pull the frame slider backwards and forwards, you will see
things happening, but it is not clear what – for that we need to
add an object. The object will rotate around the origin, so it will
work best if the object has been centred in modeller (use the F2 key).
Pick an object, load it up, and parent it to the last null in the
chain, (in this case null-roll-bank). Now if you use the frame slider
you will see it roll nicely. A simple object is best for a first pass.
If you get a twitch or jerk at frame 750, you probably missed one of the nulls being set to post behaviousr of 'offset repeat'.
If you want a longer animation, just adjust the end frame, no need to change anything else.
Sample scene:
Here is a simple sample scene with everything set up. It uses the
‘space fighter’ object as an example, which you should have
included with your LW content. If you can’t find it, just replace
it with any object of your choice. (Something a few metres across will
work without adjustments).
(Click to download scene)
Sample Video:
(MP4, 2.5 megabytes - this uses a Tie Bomber downloaded from
www.lwg3d.com)
And here's a larger clip using one of my objects:
3.5 Mb MPG4 video
Taking things further:
The sample scene has very simple lighting, as the main objective here
is the movement. Of course you can crank up the lighting settings, turn
on motion blur, and generally improve the quality.
When you replace the tumbling object, (which is not included in the
scene), you may need to allow for a different scale. The easy way is to
go to the first frame, and pull the camera back or forwards. The
spotlight is set to target the tumbling object, you may want to adjust
it's angle of illuination, or if feeling lazy, just replace it with a
distant light.
You may want to move the object that is doing the tumbling around, for example to make it fly past the camera. A
convenient way to do this is to add a new null, (maybe called
master-null), and parent to top level null in your chain to that. You
can them move the master-null around and not mess up any key frames on
other nulls.
You can adjust the speed of the tumble easily by adjusting the degree of rotation given to each null at frame 750.
If you found this tutorial interesting, you may also like to
see:
My
downloads page
Which contains quite a few Lightwave objects and scenes
for you.
My "Ringed Planet" Tutorial
Which explains how you can make a convincing ringed planet in Lightwave.
Using Poser figures in Lightwave 3d:
My
Galleries
page
Which contains quite a few Lightwave space and science
fiction images - look
under GRAPHICS
for these.
