We are having some issues with physics in UE4, to rule out anything else causing it within our project I created a small content only project with a simple blueprint that applies a upwards force to a sphere.
Unfortunately it seems it is a bug with the engine and not our project. We get Inconsistent physics simulation between PIE mode and the standalone game, this has been reported by other users [(link)].
I have uploaded a video showing the behaviour I’m taking about.
In the video, we show the test running in PIE mode and as standalone game, with smooth frame rate and fixed frame rate and with substepping on/off.
If you compare t=0:00-0:11 (PIE) in the [video]
with t=0:40-0:50 (standalone) [link]
you can see the difference in simulation with the exact same framerate settings.
So we thought, let’s try fixed frame rate @30, which well, just doesn’t work:
If you compare t=0:12-0:24 (PIE) [(link)]
with t=0:51-1:01 (standalone) [(link)]
you will also see a drastic difference between the simulations and please note the framerate of approx 100fps not the fixed 30.
We are working on 2 projects that are both heavily dependent upon physics and these issues are making our life hell for playtesting the game. We have been using the latest promoted branch (changelist 2505032) however I ran the same test project using 4.7.5 downloaded through the launcher and the problem is the same.