[ODE] Collision callback pattern

[Dave Lloyd]

Nate W wrote:

>On Tue, 2 Sep 2003, Dave Lloyd wrote:
>
>  
>
>>Thanks for the pointers, Nate. I like the approach you're suggesting 
>>here - I was having similar thoughts but I wasn't sure how to handle the 
>>mutual interaction of the two surfaces in contact.
>>    
>>
>
>To be honest, I'm not really sure either. :-)  Would the contact friction
>be the average of the two materials, or the lesser of the two?  Would
>bouncyness be the greater of the two, or the sum?  I guess the latter in
>both cases, but it's just a guess.
>
Seems like a good strategy then would be to blend the materials 
empirically according to 'typical physics' (i.e., best guess) and 
provide escape mechanisms for unusual material combinations. An 
alternative would be to provide a rule for each pair of surface types - 
admittedly more awkward to introduce new surfaces as each combination 
must be considered but I suspect in many cases there won't be that many 
surface types. Each surface type could of course be parameterised. This 
would allow us to distinguish the effect of chunky tyres on tarmac 
versus slicks on tarmac or studded tyres on ice. We may also need to 
have a finer detail description of the surface than the geom - I use a 
trimesh geom for each terrain patch (roughly 32m square) but might have 
surface details at the triangle level. Hmm.

I also like the idea of setting rules for other effects driven by the 
contacts: e.g., dust particles from rubber/sand proportional to the 
linear velocity.

Cheers,
Dave