[Opensim-dev] Prospective ODE physics changes

[Justin Clark-Casey]

Hi folks,

I'm thinking of making two ODE related changes.

1) Replace the current ODE libraries in OpenSimulator with ones compiled using the older GIMPACT collider instead of 
OPCODE.  This is to address ODE crashes in simulators with more than one region as detailed in [1] and [2].  These don't 
appear to occur with GIMPACT.

GIMPACT is apparantly less efficient, though in my own tests I was not able to notice a difference, even with many bots 
bouncing around.  The change will be reverted once/if the ODE bug can be pinned down (which may take some time), or the 
problem turns out to be something else.

2) Reducing contacts_per_collision in [ODEPhysicsSettings] from 80 to something much lower, maybe even 1.  In my own 
testing, reducing this number can halve scene physics time.  Normal avatar operations, such as standing on prims or 
walking up ramps appear to be unaffected even at 1.  However, more testing is probably needed to arrive at a compromise 
number.

Neither of these changes will affect other physics engine plugins, such as Bullet.

I'm not a physics expert so if any more knowledgeable has input into this then I'd be interested to hear it.

[1] http://opensimulator.org/mantis/view.php?id=3251
[2] http://opensimulator.org/mantis/view.php?id=4553

-- 
Justin Clark-Casey (justincc)
http://justincc.org/blog
http://twitter.com/justincc