This is a good point, though there are still some walking/standing avatars in meetings. And as there haven't been any
other significant physics changes recently or changes to the layout of WP (as far as I know) then from my testing the
collision adjustment is really the only varying change.
On 04/01/12 00:21, Dahlia Trimble wrote:
Would a Wright Plaza meeting even have multiple point collisions? Most (all?)
of the active physical objects are avatar
agents and they use capsule colliders rather than meshes. Also, most are
sitting and the few that aren't are standing on
or moving across a flat surface, probably far away from any vertex in a
collision mesh.
I suspect if you are seeing different physics statistics it's probably
something else that's contributing to it.
On Tue, Jan 3, 2012 at 1:32 PM, Justin Clark-Casey <[email protected]
<mailto:[email protected]>> wrote:
On 02/01/12 20:56, Melanie wrote:
Hi,
On 02/01/2012 21:51, Justin Clark-Casey wrote:
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.
I'm not happy with that as a general decision. We should, if
anything like that is done, include both versions to give users the
choice. The OPCODE should remain the default in order to not
jeopardize existing setups and the GIMPACT libs can be copied in by
those experiencing the bug.
Many people don't run multiregion at all and would see only
downsides if this were done.
Multi-region is a non-experimental configuration that is useful to a large
number of people. In my view, it's not
correct for out-of-the-box OpenSimulator to continue with such crashes in
the long term. This hurts adoption and
ultimate long-term success/survival.
However, it just so happens that on scouring the Internet, GIMPACT is
actually the newer collider, as per [1]. I
don't know why I thought it was the other way around - I may have
misinterpreted something that somebody said.
Indeed, apparently for our common use case (mostly static objects), GIMPACT
should perform better, so I was also
wrong about the performance issue. However, as I said, in my own testing I
haven't yet noticed any significant
difference and these questions are complex ones. But it's certainly my
experience that using GIMPACT eliminates the
ODE crashes in stress-testing, possibly due to something connected with [2]
where global object caches are shared
between collision spaces. But this is still a wild-assed guess (we can't
use TLS as OpenSim crashes immediately
upon startup).
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.
This would greatly affect scripts using physics. I believe the
optimum would be 16-20, which would ensure that the scripting
maximum (16) collision contacts are always available.
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).
Testing will continue on the osgrid plazas.
[1] http://www.ode.org/old_list___archives/2006-October/020664.__html
<http://www.ode.org/old_list_archives/2006-October/020664.html>
[2]
http://groups.google.com/__group/ode-users/browse_thread/__thread/f38c56584c650536#
<http://groups.google.com/group/ode-users/browse_thread/thread/f38c56584c650536#>
[3] http://wiki.secondlife.com/__wiki/Collision
<http://wiki.secondlife.com/wiki/Collision>
--
Justin Clark-Casey (justincc)
http://justincc.org/blog
http://twitter.com/justincc
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