[ODE] Collision impact force

[Bob Dowland]

> but this is fairly physical, and probably not a bad approximation.

agreed - there's some room for interpretation and it depends on the application and reasons for the penetration occuring - makes this an interesting question. 

having said that, is the deformation thing an argument in favour or against the penetration solution? - a squidgy bouncy ball makes less noise than a steel bouncy ball but is allowed to penetrate more because of it's higher squidgyness setting - as a result the squidgy bounces louder which is erhh wrong - or am I missing the point.

Bob.

> -----Original Message-----
> From: Adam Dershowitz [mailto:dersh at alum.mit.edu]
> Sent: 21 December 2004 18:05
> To: Bob Dowland
> Cc: ode at q12.org
> Subject: Re: [ODE] Collision impact force
> 
> 
> It is somewhat physical.  When two things that are "springy" 
> collide, then
> the penetration depth is directly related to the impact 
> force.  Maybe the
> better way to describe it, rather than impact depth, would be 
> deformation of
> the contact surfaces.  So this model is as good as the 
> assumption is that
> any collision can be modeled with a spring compression.  Real 
> impacts are
> more complex, and not just linear springs, but this is fairly 
> physical, and
> probably not a bad approximation.
> 
> -- Adam
> 
> 
> 
> 
> > From: Bob Dowland <Bob.Dowland at blue52.co.uk>
> > Date: Tue, 21 Dec 2004 17:33:00 -0000
> > To: Tyler Streeter <tylerstreeter at gmail.com>
> > Cc: <ode at q12.org>
> > Subject: RE: [ODE] Collision impact force
> > 
> > Sure thing! Although sadly I'm not likely to be trying in 
> the very short term
> > - I was just interested in hearing why you made that 
> choice. I wouldn't have
> > gone for pen depth because it's more of an artefact than a 
> physical thing (as
> > already mentioned). On the other hand, while using 
> magnitude of impulse due to
> > impact/friction seems like the obvious choice (in theory) 
> it no doubt comes
> > with an associated set of hassles.
> > 
> > There was a thread going not so long ago which threw up 
> some interesting refs
> > and analogues with fracture/breaking effects - I can dig it 
> out if you're
> > interested and/or missed it. Although those were more on 
> the synthesis side
> > rather than just volume control.
> > 
> > Bob.
> > 
> >> -----Original Message-----
> >> From: Tyler Streeter [mailto:tylerstreeter at gmail.com]
> >> Sent: 21 December 2004 16:25
> >> To: Bob Dowland
> >> Cc: stenyak at iespana.es; ode at q12.org
> >> Subject: Re: [ODE] Collision impact force
> >> 
> >> 
> >>> Tyler,
> >>> 
> >>> sounds like you've thought about this - what was wrong with
> >> "the joint feedback way" aren't the reaction mags easy enough
> >> to get hold of, too noisy, what gives - (?)
> >>> 
> >>> Bob.
> >>> 
> >> 
> >> Actually, I haven't tried the joint feedback way.  I just 
> happened to
> >> try using the penetration depth first and never got around to using
> >> the joint feedback structure.  If you do use the joint feedback to
> >> adjust the sound volume, let me know how it goes.
> >> 
> >> Tyler
> >> 
> > 
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> 
>