Detailed Verification of Physical Calculations During Simulation

[Atsushisaku]

During simulations, I’ve noticed that the fps displayed varies according to the size of the scene.
(Specifically, the larger the scene, the lower the fps.)
I would like to know at what fps the physical calculations are being performed at these times. Is there a way to profile this?
I am aware that the Physics stage setting allows for setting the Min Simulation Frame Rate.
I’m interested in understanding how the calculations are performed when the simulation fps displayed is below the set value.

[Hammad_M]

How to time codes, frames, and physics steps per second relate to each other?

The simulation stepping (“Time steps per second”) should be independent here, thats strictly defining the substepping for physics simulation. However to be confused even more there is a fifth parameter that you are missing. There is also Min Simulation Frame Rate (should be in physics settings window). Now this defines the lower bound how much physics should substep, otherwise the simulation would continuously slow down the whole application if the general frame rate is not high enough. The de…

How can I raise the frame rate of physics simulations?

Hi, yes its possible to set the simulation frame rate, on the PhysicsScene you can set the Time Steps Per Second, this defines the fixed timestep for physics simulation. The simulation will to substepping with the given timestep on the Physics Scene: [image] To speedup the rigid body simulation, most of the time is usually spend in updating back the USD, you can enable omni.physx.flatcache extension to skip USD writes and write to Fabric, that will avoid the heavy writes.

[Atsushisaku]

Thank you for your reply.
I managed to find and resolve the issue on my own based on the topic you mentioned.

[Atsushisaku]

I have an unresolved issue.

I don’t understand what “In the layer properties under ‘Time codes per second’” controls.
I understand that the number of simulation steps is determined by the “Time steps per second” within Physics.

For example,
in a simulation of a large scene with the settings: Time steps per second: 60, Time codes per second: 60, Min Simulation Frame Rate: 60, the actual callback was 19/sec.
Changing the Min Simulation Frame Rate did not alter the real-time simulation video.
However, changing the Time codes per second did affect the video.

Does this mean there’s no point in changing both the Time codes per second and the Min Simulation Frame Rate?
Could you explain the relationship between Time codes per second and Min Simulation Frame Rate, or what each controls?

[AlesBorovicka]

The TimeCodesPerSecond is the frequency at which physics gets updated from the application, so if its set to 30, then the update happens on this frequency, physics updates the positions based on this, however internally the simulation runs at the time steps per second frequency on a physics scene.
The min simulation frame rate is there to avoid doing too much work when FPS drops, however in 105.1 based applications like IsaacSim 2023.1 the time passed to update physics is fixed to the time codes per second, so the min simulation frame rate is not really used unless its higher then the time codes per second.

Ales