By Game speed acceleration, particles applied excessive Drag

vtvitzh · September 21, 2026, 4:05am

When the game speed is increased, particles with Drag applied will look different than usual.
Is this intended behavior?

Here is the reproduction project.

Pawel · September 30, 2026, 6:01pm

Thanks for reporting! Created an issue to track it:

github.com/defold/defold

ParticleFX Drag is excessively affected by increased game speed

opened 06:00PM - 30 Sep 26 UTC

paweljarosz

bug triage

**Describe the bug (REQUIRED)** When the game speed is increased, particles with… the Drag modifier applied behave differently compared to normal game speed. The drag appears to become disproportionately strong when the game is sped up, which changes the appearance and movement of the particles instead of simply making the same particle simulation run faster. **To Reproduce (REQUIRED)** 1. Open the reproduction project: https://github.com/vtvitzh/report/tree/main/20260921/Mobile%20Game 2. Run the project at normal game speed and observe the particle effect. 3. Increase the game speed as demonstrated in the reproduction project. 4. Compare the particle movement with the normal-speed version. **Expected behavior (REQUIRED)** Increasing the game speed should advance the particle simulation faster while preserving the same overall particle behavior and trajectory. Particles using Drag should therefore look equivalent to the normal-speed simulation, only progressing faster in time. **Defold version (REQUIRED):** - 1.13.2 **Platforms (REQUIRED):** - PC Forum discussion: https://forum.defold.com/t/by-game-speed-acceleration-particles-applied-excessive-drag/83252 This may be related to how the Drag modifier is calculated when the simulation timestep is affected by increased game speed. **Workaround (OPTIONAL):** If there is a workaround, please describe it here. **Screenshots (OPTIONAL):** If applicable, add screenshots to help explain your problem. **Additional context (OPTIONAL):** Add any other context about the problem here.

britzl · October 13, 2026, 6:35am

What do you mean by “when game speed is increased”?

vtvitzh · October 13, 2026, 9:17am

The intention is to increase the “set_time_step”.

In the reproduction project, clicking toggles “set_time_step” value between 1 and 4 to demonstrate the resulting changes in particle behavior.