Root Motion extraction fails to properly extract at or below 20fps

I know this is a known issue in 4.11

Does not happen in 4.10 i think. I would look for a fix in 4.12 hopefully.

Recently in our game we came across a problem where movement speeds were inconsistent on some PCs and after some debugging we found the problem only appears if fps is 20 or below. When the fps is this low the root motion from movement (and possibly other root motion animations) fail to extract the motion properly and as the fps gets lower the velocity of what is extracted gets higher.

Starting at 20fps the velocity of root motion extraction is doubled. Between 11-19fps the velocity remains at this doubled rate. Once at 10fps the velocity quadruples itself and then between 1-9fps the velocity is directly relative to each number below 10 FPS.

An interesting thing of note is that at 21fps the root motion extraction works perfectly fine but at 20fps the velocity doubles from the same root motion animation.

I’ve created a test project that shows this issue in a pretty straight-forward way for replicating it. Pressing “F” in the project will cap/uncap the FPS while displaying velocity on the UI.

Hey ,

This has been reported as UE-30178. I have added your example project to the bug report.


Hi , can you give any update on UE-30178?

Hey ,

The bug is still unresolved, but is marked as To-Do and has a lot of comment activity. They appear to have a plan on how to fix it, but haven’t finished implementing it yet.

Thank you for your patience.