[Opensim-dev] Sim and Phys Frames per Second (FPS) Issues

Mon Mar 2 22:24:11 UTC 2015

Raising the target frequency will *very likely* cause problems with many
part of the simulation involving motion. Many parts of the code assume a
11fps maximum rate and they may not be documented as such or even be easy
to understand. I *strongly* suggest that the 11fps target is *not* raised.

On Mon, Mar 2, 2015 at 1:31 PM, Diva Canto <diva at metaverseink.com> wrote:

>  BTW, I don't know why the stats reporter multiplies by a factor, maybe to
> stay backwards compatible with some perception that people expected?
> Simulation FPS is supposed to be constant. In the case of OpenSim, the user
> experience doesn't change if we increase this rate beyond 11/sec. If it
> goes below that, however, then that's a sign that the simulation is
> stressed.
>
> I refer anyone interested in this to documentation about simulations in
> general. Here's a good tutorial that I point students to in one of my
> courses:
> http://buildnewgames.com/real-time-multiplayer/
> Scroll down to the part about "game loops"
>
>
> On 3/2/2015 11:16 AM, Sean M wrote:
>
> There are 3 frame rates: *simulation*, *physics*, and *client*. Please,
> someone correct me if I am wrong: the *simulation fps* is how many
> simulation loops can be processed in a second, where each loop processes
> physics, scripting, region updates, etc; *physics* *fps* is just how many
> physics loops get processed per second, where each loop calculates
> collisions, gravity changes, and other movement updates for all appropriate
> objects in a region Both physics and simulation (phys/sim) fps are
> server-side. The fps the *client* is concerned with is graphics rendering
> on the viewer (firestorm, singularity, etc) and is literally how many
> visual frames/shots are displayed per second to the client. From a client
> point of view, 11fps is low because that is a low amount of image updates
> the client is visually seeing on their viewer. I am concerned with the
> simulation and physics FPSs being reported with highly inflated numbers. I
> want to use sim and phy FPSs as measures of how my region is performing but
> concerned that the correctionFactor of 5 is invalidly skewing these
> metrics, making both fps useless.
>
>  Michael, or anyone else, do you know why OpeSim ticks at 11 fps? Why 11?
> Is my understanding of what constitutes a "frame" correct?
>
> On Mon, Mar 2, 2015 at 1:37 PM, R.Gunther <rigun at rigutech.nl> wrote:
>
>>  11fps ? is that not very low. 22fps gives more rome or 33fps.
>> But i admit that i read fps maby wrong, and have nothing today with the
>> framerate or smoothness on the screen..
>>
>>
>>
>> On 2015-03-02 19:28, Michael Emory Cerquoni wrote:
>>
>> The reason physics and scripting are locked at 11fps is because this is
>> what the OpenSimulator heartbeat ticks at, the reason it is multiplied is
>> to satisfy the viewer statistics, I am not sure its possible to have it
>> report the legitimate numbers without some wierd side effects, but I could
>> be wrong, you would have to experiment, I suspect though that changing this
>> could lead to a lot of badness.
>>
>> On Mon, Mar 2, 2015 at 1:23 PM, Sean M <mondesire.sean at gmail.com> wrote:
>>
>>>  Greetings,
>>>
>>>  We at the MOSES project have noticed Simulation and Physics frames per
>>> second (FPS) have a few issues that we are trying to resolve. The issues
>>> are producing suspicious performance statistics for the analysis of the
>>> current version of OpenSim that we are running.
>>>
>>>  First, there is a correction
>>> factor (m_reportedFpsCorrectionFactor) that the raw SimFPS is multiplied
>>> by. The comment in the following line is a bit curious because it indicates
>>> that the FPS is artificially inflated to "lie" about the actual FPS being
>>> so low:
>>>
>>>  OpenSim/Region/Framework/Scenes/SimStatsReporter.cs: Line 317
>>>  // We're going to lie about the FPS because we've been lying since
>>> 2008.  The actual FPS is currently
>>> // locked at a maximum of 11.  Maybe at some point this can change so
>>> that we're not lying.
>>> int reportedFPS = (int)(m_fps * m_reportedFpsCorrectionFactor);
>>>
>>>  Also, lines 174 and 227 mention the use of this correction factor.
>>>
>>>  Second, this multiplier also comes into play in the Scene where there
>>> is a MinFrameTime, which seems to be the minimum reported amount of
>>> time to process a frame:
>>> OpenSim/Region/Framework/Scenes/Scene.cs:Line 723
>>>
>>>  Both of these variables, the correction factor and MinFrameTime, are
>>> concerning from a statistics view point as they are generating skewed and
>>> massaged numbers; therefore, I have a few questions:
>>>
>>>  1) Is it commonly known that Sim and Phy FPSs are inflated to maintain
>>> the "lie"? And if so, will it be corrected to be an accurate reporting of
>>> processed frames per second?
>>>
>>>  2) What exactly are the definitions for OpenSim's Simulation (Sim)
>>> FPS, Physics (Phy) FPS and a frame (I have found conflicting and vague
>>> definitions on the wiki)?
>>>
>>>  3) What are the known performance consequences of setting the m_reportedFpsCorrectionFactor
>>> to 1 and MinFrameTime to 0?
>>>
>>>  Thanks,
>>> Sean M.
>>>
>>> _______________________________________________
>>> Opensim-dev mailing list
>>> Opensim-dev at opensimulator.org
>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev
>>>
>>>
>>
>>
>> --
>> Michael Emory Cerquoni
>>
>>
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