Laurent Couvidou

A couple months before release, QA reported that we sometimes had enemies stuck inside inaccessible buildings. You couldn’t see them normally, but AR markers revealed that they were living behind walls. Using the debug cam, we saw them wandering inside sealed, unlit buildings — and had no idea how they got there. 2/n

At first we thought it was an asset issue. We checked the spot where the issue was the most frequent, and found a static mesh instance not flagged to carve the nav mesh. This affected lower LODs using nav mesh walking and ignoring collisions. We sorted that out. It didn’t fix the bug. It became less frequent, but still occurred here and there, with no faulty data around. The plot thickened as the release date approached. 4/n

Despair was close. Impossible to debug: never in editor, never on camera. So we built a small tool to record the full movement history. Finally, we saw the paths that led them inside buildings. They were always straight, 2-point paths. Leading right through collisions, ignored due to nav mesh walking. That was the final piece: these paths were an artefact of crowd avoidance that should not have been used as-is, but LOD shenanigans made them slip through. 6/n

We fixed it. QA confirmed. Massive relief. We shipped with too many bugs (see: the whole Internet back then), but *not* this one ✌️ 7/7 The End

@fn0rd Obviously you are not addressing the right problems, duh

There was no way they could have pathed inside, and yet somehow they did. It might sound minor, but in some cases you have to kill all enemies to progress, so this was a nasty mission blocker 😬 It only happened in a handful of places, seemingly randomly. But we knew it only occurred after scouting with the companion drone in manual control, which puts our LOD systems under a lot of stress. It was fairly rare, maybe once every other day across QA tests. 3/n

Further investigation pointed to level streaming. MindsEye loads geometry as you move about, bringing its own complications. So we took a big swing: abort path following whenever an NPC froze due to streaming. It reduced the frequency. But again, it didn’t eliminate it. Now it was just very, very rare 🥹 5/n