Thanks. You have clarified much. I realised the rift is viewer control but was not so clear about the impact/relationship between viewer and server frame rates and the interpolation needed.
Thanks again. Tom Willans BSc(Hons) MBCS CITP Chartered IT Professional Managing Director Bessacarr Publications Ltd +44 (0)121 288 0281 email: [email protected] skype: tom.willans Second Life and OSGrid: Tom Tiros Sent from my mobile > On 3 Mar 2015, at 09:08, Dahlia Trimble <[email protected]> wrote: > > If my memory is correct, SL sims run at a default of 45 frames/second. > OpenSimulator runs at 11. I'm not certain exactly why 11 was chosen but I do > know that increasing it increases the amount of work the simulator must do. > E.g., if you go from 11 to 45 you quadruple the work the simulator must do > > The only signal I'm aware of that affects the viewer is "time dilation". This > value varies from 0.0 to 1.0 where 1.0 indicates the simulator is running at > full speed. If for some reason the physics engine cannot keep up with the > simulation it can signal the viewers to slow movement. This value is sent > with many UDP packets that are involved with the scene and moving objects, so > the viewers will know this value as timely as possible. > > Running the simulation at 11 fps shoudl *not* affect devices such as the Rift > as the camera is controlled entirely viewer side except under special > circumstances such as a user surrendering camera control to a script. The > viewer frame rate is *entirely independent* of the simulator frame rate and > will run as fast as the hardware allows if configured to do so. > > Choosing an appropriate simulation frame rate would involve weighing the > tradeoffs between simulation workload and responsiveness to user controls > such as those that control avatar position movement. Bear in mind that there > are also network delays involved; a simulation running at 11 frames/second > will respond to a user control every 89 ms but there will also be round-trip > network delays which may typically be 100-200 ms but as high as 1.5 seconds > or more. Increashing the simulation frame rate will likely not produce a > perceivable difference in performance but will *significantly reduce* the > capacity of the simulator to do things like host more avatars and scripted > objects. > > Also bear in mind that much of the code assumes 11 frames/second and raising > that may create motion-related and other bugs that may not be apparent until > much later. OpenSimulator is tuned to function properly at 11 frames/second. > > To recap: the user camera is for the most part entirely controlled within the > viewer and is unaffected by simulation frame rate. As such devices such as > the Rift which manipulate the camera will not be affected. > >> On Tue, Mar 3, 2015 at 12:09 AM, Tom Bess <[email protected]> wrote: >> >> 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 >> +44 (0)121 288 0281 >> email: [email protected] >> skype: tom.willans >> Second Life and OSGrid: Tom Tiros >> >> Sent from my mobile >> >> >>> On 3 Mar 2015, at 05:18, Sean M <[email protected]> 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 <[email protected]> >>>> 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 >>>>> [email protected] >>>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev >>>> >>>> >>>> -- >>>> Justin Clark-Casey (justincc) >>>> OSVW Consulting >>>> http://justincc.org >>>> http://twitter.com/justincc >>>> _______________________________________________ >>>> Opensim-dev mailing list >>>> [email protected] >>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev >>> _______________________________________________ >>> Opensim-dev mailing list >>> [email protected] >>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev >> >> _______________________________________________ >> Opensim-dev mailing list >> [email protected] >> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev > > _______________________________________________ > Opensim-dev mailing list > [email protected] > http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev
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