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

[Tom Bess]

I am reporting a comparison between sl and opensim and did not realise this. Does sl run at a true 55fps? If so why bother?  Presumably the viewer needs 55fps sent to it to get its calculations correct as at 11fps opensim does the same at sl albeit in larger steps. 

Would a faster fps improve the accuracy of devices such as the rift by having to interpolate over a shorter period of time? Admittedly I suspect viewer rendering needs to be improved as well as this aspect is holding my experience back. 

I understand that other aspects may assume that 11fps is a fixed constant and not allow for this to change presumably that can be changed but you guys know more here.

Thanks for the guide btw. 

Tom Willans  BSc(Hons)  MBCS  CITP
Chartered IT Professional

Managing Director Bessacarr Publications Ltd
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> On 3 Mar 2015, at 05:18, Sean M <mondesire.sean at gmail.com> wrote:
> 
> Thanks Justin, Dahlia, Michael, and everyone. I now have a better understanding of the way FPS is calculated and of the correction factor. 
> 
> -Sean M. 
> 
>> On Monday, March 2, 2015, Justin Clark-Casey <jjustincc at googlemail.com> wrote:
>> I think this has already been said but just to summarize.
>> 
>> * The 11 fps are the number of scene frames processed - opportunities where avatars may be notified about changes in the scene.
>> 
>> * Each of these scene frames is associated with a physics process where 5 physics frames are processed in each frame. Hence 11 * 5 = 55 fps.
>> 
>> * Why this number?  Others may know better but my guess is that it's related to the frequency of updates expected by the viewer.  Teravus may well know more if he's still around.
>> 
>> * Changing m_reportedFpsCorrectionFactor will do nothing except change the server FPS stat.
>> 
>> * Changing MinFrameTime will change the number of scene frames.  From my work in the past, you would also need to adjust other parameters like physics frames to stop things going haywire (this was with ODE, Bullet might work differently).  I expect you also wouldn't gain much if anything in scene fidelity.
>> 
>>> On 02/03/15 18:23, Sean M 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
>> 
>> 
>> -- 
>> Justin Clark-Casey (justincc)
>> OSVW Consulting
>> http://justincc.org
>> http://twitter.com/justincc
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