Light ROM 4/Light ROM 4 - Disc 1.iso/text/maillist/1996/012296.doc/[e-mail] _Fri Jan 26 22:57:41 1996.msg

Internet Message Format | 1996-02-04 | 6KB

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From: [e-mail] (Christopher Eric Hanson) ()
To: Multiple recipients of list <[e-mail]>
Subject: Expressions as a Plug-In (Re: Lightwave convenience feature...)
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In article <[e-mail]> Christian Aubert <[e-mail]> writes:
> One way of doing this that would be really cool is through expressions
> like Alias doest it. You can define a motion channel for an object as a
> relation to another object's. For example:
> Wheel:Z_Rot = Car:X_Trans * ( 4 (wheel diameter) * 3.1416 (pi) / 360)
> You can get some really cool effects this way, like control panels for
> characters!

  A friend of mine who works at Disney, and gave us a demo of their
Alias setup when we were in LA for VTU Expo. Disney uses Alias' expressions
heavily, to set up such control panels that modify and operate complex
character motions and deformations.

  The way this works is to take a simple object (say, a sphere) and
place it somewhere out of the visible scene. Call this object KnobA.
Now, you can set up expressions that correlate the motion of other objects
(or NURB control points) as functions of the motion of this KnobA.

  LeftInnerEyeBrowCtrlPt:Y_Trans = KnobA:Y_Trans
  LeftOuterEyeBrowCtrlPt:Y_Trans = (KnobA:Y_Trans * .6) - .2
  LeftMidEyeBrowCtrlPt:Y_Trans = (KnobA:Y_Trans * .9) + .4
  LeftMidEyeBrowCtrlPt:X_Trans = KnobA:Y_Trans * .1

  My syntax may not be perfect, but what this means is that as you slide the
KnobA up and down on the Y Axis, the inner, outer and mid control points of
the Left Eyebrow all move up and down by varying amounts. In addition, if
you look at the last line, the mid eyebrow control point moves outward just
a little as the eyebrows go up.

  So, complex motions can be designed by the model designer, and codified
into simple knobs. Then, the model designer gives the character to the
animator, who just has to twiddle with these knobs to make the character
dance.

  The whole thing is keyed by moving the knob object around and keyframing
_it_. Special tweaks can be done on the object itself where necessary,
but the major of actions on a well-designed character can be executed
with just the 'control panel'.

  Virtual marionettes.

  At Disney, they will have a huge View (Alias has multiple simultaneous
3D Scene Views) open on a 1280x1028 SGI display, just filled with these
knobs for a given character. The object designer typically puts a simple
square container object around each knob to indicate the 'useful' range of
the slider, beyond which the object starts to deform or wig out. Also, they
have some method of putting simple bitmapped text adjacent to each knob
to indicate what it controls: Smile, Step, lean, sniff, eyebrow, look
direction, etc. And many knobs (like look direction) are multi-axis,
where you can cause the character to look around by sliding the knob
on the X and Y axis.

  The general opinion on Alias at Disney was that it was a big slow pig,
but that Disney is sticking with it for the Expressions capability. My
contact (who shall go unnamed, in case I've divulged something proprietary)
thought that Lightwave might have a good chance at some of the projects
they did if it could support something like this.

  I believe something like this could be fairly easily implemented
(almost trivially) as a Lightwave motion class plug-in. (In fact, I
think Real3D has had this for a while, but no one every understands
that program. Besides, I think you have to write scripts in RPL to
do it in Real3D).

  I'd like to write one of these myself, but I already have too many irons
in the fire. Maybe BML Bob or someone else is looking for a killer
plug-in app.

  As an aside, it would be even slicker if instead of having to use
polygon wasting spheres and boxes and text objects, you could actually
dynamically create a GUI for each character that had real sliders and
knobs and labels on it.

  Any nibbles? Do any other character animators think this is an
effective way to animate? I guess it'd even be pretty useful to the
mechanical brigade and all their walking robots and spaceships and
stuff. One knob that says "Landing Gear", and when you slide it from
top to bottom, the wheel covers unfold, the gear extracts out and the
landing lights deploy.

  I imagine you could probably even put a field in to specifiy which
_frame_ to steal the motion from. That way you could easily set up a
row of objects that all did the same motion, each 12 frames behind the
previous.

  The possibilities are... DBL_MAX.

>  Christian Aubert - 3D Art Tech        750 Cote de la Pente Douce
>  http://www.megatoon.com/~chris               Quebec, PQ, G1N 2M1
>  email:[e-mail]                   vox:418-527-3636 #236
>  Megatoon Studios Inc                       fax:[phone]

Chris - Xenon
--
 Chris Hanson | [e-mail] | I've got friends in low latitudes!
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