If throttling happens, rendering won't act correctly (speed for entities).

[Norlock]

Bevy version

0.6.1

https://github.com/norlock/sparticles-bevy/tree/bug-more-particles
8c6bf7559b3ec8fc1a7ad3a378ef62427408b7ca

Operating system & version

I use Arch on Wayland.

What you did

In main.rs there is a field I changed:
particles_per_emission: 200,

If you change from 20 particles_per_emission to 200 you can see it will start to drastically increase in speed.
I use delta in transform, and turned off all animations / forces to turn off external factors.

What you expected to happen

That it won't drastically speed up if it starts to throttle but stay in range of its actual speed. I can understand if it stutters but not to speed up.

What actually happened

It will start to speed up.

Additional information

[alice-i-cecile]

8c6bf7559b3ec8fc1a7ad3a378ef62427408b7ca (bug-more-particles branch)

I think you intended to link to one of your repos here? I'm having a hard time understanding what you're trying to report.

[DJMcNab]

8c6bf7559b3ec8fc1a7ad3a378ef62427408b7ca isn't an object in my local clone of bevy's repository, and neither GitHub nor Google give any results for commits with that hash.
Additionally, the string particles_per_emission never appears in the bevy respository, and "bug-more-particles" bevy also gives no results.

[Norlock]

I added my repository I forgot, but what I'm trying to explain is that somewhere if it starts to throttle (by changing particles to 200), the movement speeds up. Maybe I'm too inexperienced with gamedev and not really grasping what is causing it. I thought the delta I added in the transform system would mitigate the changes in frame performance and that it shouldn't visually appear to speed up (in this case movement of particles).

[alice-i-cecile]

So, questions for help with specific problems belong in Discussions. I'm going to convert this to a discussion. If you can identify a clear bug in Bevy's code with a minimal reproduction, please feel free to file a new issue.

[DJMcNab]

What's happening in your program is the interaction between Time and FixedTimeStep.

The delta_seconds in Time is only updated every frame.

However, due to your fixed timestep, the system transform_particle_system runs multiple times each frame, but with the delta between each real frame each time.

The easiest way to fix this will be to use the delta of 1./60. instead of time.delta_seconds() in transform_particle_system.

In the future, we'll want to make this issue more difficult to run into. Basically, Time::delta_seconds is currently reasonably meaningless in a system controlled by a FixedTimeStep