[4.5] Navigation Mesh Rebuild At Runtime causing 20-40 fps loss in 4.5 only

#Repro

  • Make a large level with a very large nav mesh
  • project settings-> nav mesh → rebuild at runtime

Reload editor, and make sure the “building navigation” message lasts at least 10 seconds

  • construct a reasonably complex scene that takes fps below max on your machine

  • do this in 4.3 and in 4.5

  • observe difference in FPS while nav mesh is rebuilding itself in 4.3 vs 4.5

  • create some actors during runtime via key press, in 4.3 and 4.5, that have CanEverAffectNavigation set to true

Result = endless loss of FPS in 4.5 as long as you keep triggering navigation mesh to rebuild

So what this means for me is

#I have to revert to 4.3 until this issue is fixed

I can’t test actual fps drop of other game mechanics until this issue is fixed, and so I must revert to 4.3, because AI is stage of development I am most focused on right now.