[Opensim-users] Opensim Performance

Sun Dec 7 00:00:55 UTC 2014

Sure, a mesh chair is a good example. Thr visible chair can have hundreds,
even thousands of triangles in a small area. It may not be necessary to
make them completely phantom however. Using a simple cantilever shape for a
collision mesh could provide semi-realistic collisions for many cases and
probably would not require much work from the CPU. Such a shape could be
uploaded along with the chair mesh.

It's probably also worth considering that the goal of the OSCC regions was
to accommodate 100 avatars reliably in a single region, so any measures
that were taken to eliminate any unnecessary CPU overhead likely had a
strong influence on reliability.

On Sat, Dec 6, 2014 at 3:21 PM, Mister Blue <misterblue at misterblue.com>
wrote:

> For BulletSim, collisions between terrain, spheres, and boxes is an easy
> computation. Collisions with meshes is a lot more computation. For
> instance, the OSCC conference has a whole bunch of high resolution (large
> mesh) chairs. The CPU to compute collisions with them was noticeable. In
> that case, all the chairs were set phantom to save CPU time.
>
> In general, avatars on terrain or blocked structures should not create
> noticeable overhead. When you add meshes, you might have to consider
> phantoming some things.
>
> -- mb
>
> On Fri, Dec 5, 2014 at 1:32 PM, Dr Ramesh Ramloll <r.ramloll at gmail.com>
> wrote:
>
>> Thanks Dahlia :)
>>
>> On Fri, Dec 5, 2014 at 4:05 PM, Dahlia Trimble <dahliatrimble at gmail.com>
>> wrote:
>>
>>> A lot depends on where the "physical" (moving, rigid objects or avatars)
>>> are relative to the static (non-movable) non-phantom objects. Collision
>>> testing can be a significant part of simulation load. It generally happens
>>> in multiple phases: a "broad phase" where any moving objects' sizes and
>>> positions are compared to other objects to see if they are close enough to
>>> warrant more precise testing, and a "narrow phase" where any potentially
>>> colliding surfaces are tested. If your scene is set up so that you have
>>> many complex collidable (non-phantom) static objects but all of your
>>> avatars are not near them then collision testing load should be fairly low.
>>> However if they are all standing on colidable objects made of hundreds of
>>> small prims then collision testing load will be much higher. Some prims
>>> and/or mesh models can have thousands of triangles which could each be
>>> subject to collision testing.
>>>
>>> In general if you have very complex objects it's probably better to make
>>> them phantom and superimpose a simpler, invisible shape which can be used
>>> for collisions. The mesh uploader in most viewers offers an optional
>>> "physics mesh" which could be used for this purpose as well. However, if
>>> simulation CPU load is not an issue for you then you could probably get
>>> away with ignoring such optimizations although considering how content is
>>> often repurposed it could be considered a best practice to use them.
>>>
>>> On Fri, Dec 5, 2014 at 12:16 PM, Dr Ramesh Ramloll <r.ramloll at gmail.com>
>>> wrote:
>>>
>>>> Hello there,
>>>> As I was reading about opensim performance on the opensimulator.org
>>>> site, I came across these two recommendations
>>>>
>>>>    - Make as many objects phantom as possible. Phantom objects do not
>>>>    need to be tested for collisions with avatars and other objects, reducing
>>>>    physics frame time and increasing performance.
>>>>    - Make as few objects subject to physics (e.g. falling under
>>>>    gravity, movable by other avatars) as possible. Physics objects need a lot
>>>>    more collision testing than ordinary non-phantom objects.
>>>>
>>>>
>>>> I understand these appear fairly logical. I am curious though, are
>>>> these differences really going to make perceptible improvements in user
>>>> experiences? Are there any metrics that would say help us know when to
>>>> start converting unnecessarily physical objects to phantom?
>>>> Thanks
>>>> Ramesh
>>>> --
>>>> 'Consider how the lilies grow. They do not labor or spin.'
>>>> *Rameshsharma Ramloll* PhD, CEO CTO DeepSemaphore LLC, Affiliate *Research
>>>> Associate Professor*, Idaho State University, Pocatello, ID 83209 Tel:
>>>> 208-240-0040
>>>> LinkedIn <http://www.linkedin.com/in/rameshramloll>, DeepSemaphore LLC
>>>> <http://www.deepsemaphore.com>, RezMela <http://www.rezmela.com>, Google+
>>>> profile <https://plus.google.com/103652369558830540272/about>
>>>>
>>>> _______________________________________________
>>>> Opensim-users mailing list
>>>> Opensim-users at opensimulator.org
>>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>>>>
>>>>
>>>
>>> _______________________________________________
>>> Opensim-users mailing list
>>> Opensim-users at opensimulator.org
>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>>>
>>>
>>
>>
>> --
>> 'Consider how the lilies grow. They do not labor or spin.'
>> *Rameshsharma Ramloll* PhD, CEO CTO DeepSemaphore LLC, Affiliate *Research
>> Associate Professor*, Idaho State University, Pocatello, ID 83209 Tel:
>> 208-240-0040
>> LinkedIn <http://www.linkedin.com/in/rameshramloll>, DeepSemaphore LLC
>> <http://www.deepsemaphore.com>, RezMela <http://www.rezmela.com>, Google+
>> profile <https://plus.google.com/103652369558830540272/about>
>>
>> _______________________________________________
>> Opensim-users mailing list
>> Opensim-users at opensimulator.org
>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>>
>>
>
> _______________________________________________
> Opensim-users mailing list
> Opensim-users at opensimulator.org
> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://opensimulator.org/pipermail/opensim-users/attachments/20141206/00d8be83/attachment-0001.html>