Any idea why the speed of effects are related to the Frame rate in UE4?


I’m having some issues where my effects speed are tied to the FPS and not the game time in UE4. Did anyone has encounter a similar bug before? Is it well know?

There’s these settings we can edit directly in Cascade :


But it looks like in my project… it has been hardcoded to FixedTimed :thinking:

Almost everything in UE4 is tied to FPS, it’s not really a bug - it’s more like a design specification.

Fixed timestep is actually quite a big and ancient problem in programming, especially in context of creating game engines. You may google it up if you’re interested in it, but be ready for walls of hardly understandable code.

As long as your FPS doesn’t jump, like, from 20 to 120 - it shouldn’t really be a problem: it’s just some graphical effects we are talking about after all.

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Thanks for the reply @LudeosShaft

So, the better the hardware the faster the effects will play? We’re testing our game on different specs and it really shows up! We’re seeing like up to 3X the speed we’re developing into Cascade! I’ve never experience that before with Frosted or Unity.


This really shouldn’t be the case, under the hood particle movement is deltatime based in the RealTime Settings.

FixedTime uses fixed time intervals for the math, which makes it speed up or down with framerate. Unless you will have fixed framerates for sure, you really don’t want to use this setting.

So, as you pointed out earlier, best you track down who on your project, decided to put it on FixedTime, and have a chat with them to see what can be done.

(Note: Fixed time steps are usually only used for cinematics and related effects, you can make sure certain beats of your effect always align with the correct frame of the cinematic. Note2. This is just from my experience, maybe other people have other uses for it.)

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