There is some strange issue with CCD where constrained CCD objects can get velocity nulled when hitting things while constrained, its very hard to reproduce normally in engine but happens often in VR with constrained objects (FPS difference?). For example, two swords constrained to motion controllers will hit each other and then stop and just float slowly in circles around each other, pretty much ignoring their constraints until they eventually just unfreeze. This ONLY happens with CCD enabled, even if the same motion with CCD disabled leaves them still in contact and not tunneling.

User made the reproduction project using the built in physics handles for the moving sword.

This was reported and tested in 4.23.1 (CL-9631420). This was reproduced in 4.22.3 (CL-7053642), 4.24 (CL-9756633), and Main 4.25 (CL-9757446)

Steps to Reproduce
  1. Download and open the attached project'
  2. Play In Editor

Results: The four swords on the right have CCD enabled, the four on the left do not. Intermittently the swords with CCD enabled will start some weird zero velocity interaction where they float around each other.

Expected: The swords should all behave roughly the same aside from tunneling in the non CCD swords.

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Won't Fix
ComponentUE - Simulation - Physics
Affects Versions4.
CreatedOct 23, 2019
ResolvedOct 30, 2019
UpdatedMay 8, 2020
View Jira Issue