Subject: Re: beachball on the water
From: [email-masked] (Gord Davison)
To: Multiple recipients of list <[email-masked]>
Date: Sat, 27 Apr 1996 01:04:47 -0700

Dennis Harp wrote:
>> A small, floating object influenced only by gentle (harmonic) wave
>> motion would generally move in circular motion as each wave passes.
>> This is because the buoyant force will develop horizontal components
>> as the surface of the liquid becomes other than purely horizontal.

Ernie wrote:
> There must be engineering models of this.  I'd think you could calculate
> a gradient for the water surface and use that to derive a mix of rolling
> and sliding for the beachball.  A job for a plug-in, although it's not
> immediately obvious to me how it would be implemented.

A plug-in of this nature might be interesting to do. It could also serve as 
a useful example of how complex models can be simplified for "artistic 
effect". A case in point is the LW implementation of motion blur: it's not 
the true "lens" method [description for another post :-)], but rather it is 
accomplished by multiple offsets of the object composited together [right?].

Fluid dynamics can get pretty complex [i.e. density, pressure, buoyancy, 
surface tension, viscosity, turbulence, etc.]. There's a healthy dose of
wave theory to deal with as well. Thankfully, many of these factors would have 
a negligible role in a simplified "ideal" model situation such as this. Still, 
it would pose an interesting challenge to implement such a plug-in :? 
NB. The fact that it's not immediately obvious to _Ernie_ is evidence of the 
*challenge* involved ;-).

==========================================================================
 Gord Davison                      | 2D/3D Animator � Multimedia Designer
 Phoenix Interactive Design, Inc.  |
 graphics � animation � multimedia |   "Complex problems have simple,
 [email-masked]             | easy-to-understand, wrong answers."
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