heartbeat loop time and physics step time

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heartbeat loop time and physics step time

AJLDuarte
Heartbeat loop time close to 100ms and physics step time close to 20ms
correspond to acceptable values for the simulation of "social life" type of
in-world interactions.

OpenSim does support other values for other uses and contrary to what was
written here, faster heartbeat has positive impact on the simulation result.
Simulation and network loads do not scale as fast as heartbeat rate.

Heartbeat does not control many aspects of the simulation timing, it does
control the rate at most entities updates are sent.
(It does not control all updates because the default 100ms wasn't good
enough and so bypasses where added)
 
If you don't want to pile up dozen of regions on a Atom class CPU machine,
and do want to have some simulation of moving objects, you should try to
reduce heartbeat loop time. 22ms is a typical value, in fact several forks
of OpenSim do use it as default.

Simulation inducing high stress levels on users may require overall fps well
above 100. But this is just a comment, well outside current OpenSim, in fact
many commercial games capabilities.

Physics simulation time step is another valid configuration option except on
legacy ODE.
Dahlia warning about timing assumptions are absolutely valid in legacy ODE.
its time step must be around 20ms.
On new ode this may be used within reason to reduce the consequences of ODE
not having CCD.

Region owns or grid managers should test the best values for that specific
region needs. OpenSim Defaults are just basic safer options.
Since reported FPS is mainly for scripts and users, the multiply factor
should be also configurable or automatically set so to report the nominal
legacy fps they expect.

Regards,
Leal Duarte (Ubit Umarov)

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