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Pathfinding Questions

On Aug 6, we sent a series of questions to Linden Lab, concerning Pathfinding; we got answers back - here they are.

  • If region owners disable PF on their regions, will the next roll out re-enable it?
    LL: “No. This data is stored as a simstate variable and will persist with the region unless re-enabled by the user or an explicit override provided by us.”
  • Given the math changes, PF regions will potentially be able to have more prims, if a region owner adds more prims and 3 months down the road turns off PF, will prims begin getting auto returned?
    LL: LL “No. The ability to enable/disable pathfinding has no effect on the land impact formula.”
  • Will disabling pathfinding fix broken vehicles due to SVC-8048 or does it stay on the same havok version when disabled so they will be broken anyway?
    LL: “Toggling dynamic pathfinding will have no effect on vehicle physics”
  • Two regions next to each other, region A disables PF and region B keeps it on, will vehicles passing between them break.
    LL: “Toggling dynamic pathfinding has no effect on the Havok version being used by the simulator and there no effect on mesh object transmission between regions.”
  • Will disabling PF cause PATHBUG-156 to happen?
    LL: “No. Only server code change or unlinking/relinking an object should cause that to happen.”
  • What does PATH-794 and PATH-787 actually cause? Seeing as those issues are hidden.
    LL: “PATH-794 refers to a problem caused by setting a parcel to “Linden Content” whereby the parcel's “no object entry” flag is cleared. This can only be done by Lindens and should not be a concern outside the lab. PATH-787 refers to a bug where, given a parcel set to “no object entry” on region A which borders another parcel on region B, the characters may attempt to cross from A to B or vice versa when that should not normally be permitted (and is not permitted if both parcels are on the same region). This is a bug that we will hopefully fix in an upcoming maintenance release but which is not severe and is not expected to be a major source of problems.”
  • Does a region need a reboot after enabling and disabling PF? What bits are actually disabled & not disabled?
    LL: “Yes, the region must be restarted. Only “dynamic pathfinding” (i.e., updates to behavior driven characters and updates to the navmesh based on movable obstacles) is disabled by the setting.”
  • What performance stats did you get for unoptimised regions/optimised regions & does there look like there will be a problem with unoptimised regions?
    LL: “The theoretical worst case behavior should be about 4ms worse for full regions on average and 1ms worse for homesteads on average. Individual frames may spike significantly higher but we have not seen anything very noticeable as a user. If an unoptimised region region experiences significantly worse performance than that, the problem can be resolved by disabling dynamic pathfinding.”
  • How did Homesteads perform on PF when unoptimised?
    LL: “Homesteads have been throttled to allow only 1ms average to be devoted to navmesh updates. If an update during one frame takes longer than this, updates in subsequent frames will be skipped to bring the average in line.”

For details on known Pathfinding issues, please refer to this page.

pf_questions.txt · Last modified: 2013/02/19 01:12 by miro.collas