[Opensim-dev] Prospective ODE physics changes

[Justin Clark-Casey]

The current ODE library is already post 0..11.1 (r1755).

On 03/01/12 22:28, M.E. Verhagen wrote:
> Maybe it is a good idea to also update the ode to the 0.11 version ?
>
> 2012/1/3, Adams, Robert<robert.adams at intel.com>:
>>> ...
>>> According to [2], the maximum reported scripting collision contacts is 8.
>>>
>>> Testing with 8 on Wright Plaza today in the Tuesday meeting seemed to
>>> greatly reduce physics scene time compared to
>>> previously without any apparent loss of required fidelity (50ms with 18
>>> avatars, albeit mostly sitting down -
>>> unfortunately I didn't record previous week's numbers but they were
>>> higher.  Nebadon tested one of his vehicles).
>>
>> Looking at the code, contacts_per_collision is the number of collision
>> points reported by ODE for each collision -- like a prim sitting on rough
>> terrain and touching multiple places on the ground. Reducing the count to 8
>> means that no more than 8 contact points will be reported by ODE and, if
>> there are more, you can't be sure you get the 'best' ones.
>>
>> I suspect that most of the time there are only a few contact points so it
>> doesn't make sense that reducing the number from 80 to 8 would significantly
>> reduce the compute time. If it is the number of contact points causing the
>> computation overhead then ODE must be normally returning more than 8 contact
>> points. Is this really the case? Or is something else going on?
>>
>> -- ra
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Justin Clark-Casey (justincc)
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