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phaedra Exonar

Pathfinding Q&A

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Found this on the phoenixviewer web page, has some info on the separation of pathfinding and new physics changes, good to know if you want to turn off pathfinding, all so they have the instructions to turn off pathfinding if you wish to do so.

http://wiki.phoenixviewer.com/pf_questions

http://www.phoenixviewer.com/

If regions have to be manually optimized, why isn't LL putting this info in the face of every land owner, currently only people who read the server forum or have an interest in pathfinding are like to even know about this.

 

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Speaking as a landowner, I've been aware of this for ages.    That's because tier on sims represents quite a significant outlay and rentals on them represent quite a significant income, so I make a point of keeping up -- via the server forum,  the wiki, knowledge base, blogs like Nalates' and Inara Pey's and discussions in SLU -- with what's going on.

In point of fact, while I've turned off pathfinding as a precautionary measure, until I can make time to optimise stuff, everything I'm being told by people who know far more about it than do I suggests that I'm being over-cautious, in that having it turned on or off isn't going to make any difference unless people start introducing pathfinding objects onto the sim and, even then, in practice I shouldn't notice any ill-effects from not having optimised the sim other than that the pathfinding objects weren't performing as well as they might.

 

 

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I am a little concerned that Tara Undercroft feels that this is not appropriate for the Server Blog, what ever does Pathfinding concern if it does not concern Servers??

I cannot help mumbling to myself about sweeping and carpets.

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But I thought that phaedra was complaining that "currently only people who read the server forum or have an interest in pathfinding are like to even know about this."   So isn't moving it to the General Discussion Forum, in order that people who don't normally read the server forum may become aware of it, too, a sensible thing to do?   Or am I misunderstanding something?

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turning off path finding in your region will not effect anything. It won't help with performance issues related to path finding and it won't fix any of the glitches the new code has introduced. The only thing it does is disable the ability to use pathfinding characters on your region.


And from what I can gather the pathfinding code should not effect your sim performance anyway, unless you are using it. The only reason to optimize your sim for path finding would be if you were actually running path finding characters on your sim. Then you would want to optimize how they interact with the land and prims they are moving around.

Pathfinding completey fubared our race race cars and drag strip. So I have been playing to see what effects it really has on the sim and stuff on it. Turning off path finding did nothing, nada, no difference. Sim performance was the same and everything that was broke is still broke. Optimizing it via the bulk setting also did nothing. Ok it did do something, it broke every vehicle that was currently out because I set it to static object instead of movable. But either way it didn't change sim performance, even by a .01 MS. And manually going trhough and trying optimize it didn't do anything either.

Then again we are not running any path finding characters on our sim.

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It is my understanding that turning off Pathfinding will not make a blind bit of difference to the problems many are experiencing. Pathfinding required an upgrade to the Havok 7 physics engine, and that upgrade breaks a lot of existing content. Some of us may be lucky. Some of us will not be.

&Unfortunately, from what I've seen of the trial on the Magnum RC, Pathfinding has only been tested for fish.

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I originally posted the link because I thought they might answer some of the questions people were asking in the server forum, I added that comment at the end, because once again many of the answers that people need are there, but not easy to find. Now that the post has been moved it shows in both places which works out better.

I've been testing path finding scripts for months now, but I only own a small parcel of land on the main land, so wasn't able to opting in to enable path finding on my land early.  Some one with a full sim has a lot more options for dealing with path finding.  For some one on a sim with out a single region owner theres no option to turn it off so optimizing is our best option. 

The sim I'm in has 2 other land owners, one of them is LL.  Each owner will need to optimize their part of region.  Small land owners are the ones to must likely not be aware of all the changes, it seams to me that the the path finding info should have been made more visible for every one.  Especially since the default setting for objects is the least efficient from my understanding. 

 

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Heavens above.. now we're back on the Server forum!

This is getting silly.

I don't know that the default setting for scripted objects -- moveable obstacle -- is the least efficient.  It's certainly the safest, since if you set something that actually needs to move -- a door, for example -- to static obstacle, then it can't be moved by script (and it throws an error if the script tries to).

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Innula

It may be my comment that brought the thread back to the server forum.  I did think that since Pathfinding is a server issue folks would look for a server blog...it seemed logical to me.  But there's a real mess out there in SL and a lot of folk are yelling about bandwidth.

I have noticed that on sims where there is little or no "spare time" that the sim tries to send the data over a hugely inflated bandwidth (up to 4Mbps) which is way beyond SL's own servers' capacity.  Now this needs some attention because folk are upping their own bandwidth to try to help and it does no such thing.

The problem does not occur if the sim has a few ms of spare time.  I think LL knew about this and simply warned sim owners that this might be a problem.  Whether they expected to see this bandwidth issue I do not know.

Coupled with the issue over traffic calculation (SVC-8099) I think there is a real thunderhead of resentment building.  The sky may not be falling but it sure looks like rain!

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What's the bandwidth issue?  This one's new on me.  

My understanding of pathfinding and updates -- gained mostly from Nalates, who's been following it very closely -- is that the way pathfinding's set up, if updates to the NavMesh are going to have a bad effect on region performance, they wait until the region's less busy,  so pathfinding objects may start behaving strangely but other things shouldn't.   

As an addition to the resources phaedra posted, I'd add this Pathfinding Overview by Inara Pey, Nalates' discussion of Second Life Pathfinding Performance (linked to above) and Lorca Linden's detailed comment on Nalates' article (in which I'm delighted to see he says they're going to update the information in the wiki, which has left me utterly confused as it stands).   

I agree about traffic calculation, which is a nightmare, but that can't be to do with pathfinding, surely?

 

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Innula Zenovka wrote:

Heavens above.. now we're back on the Server forum!

This is getting silly.

it's path finding for the forums, you need to set a post to "static post" to keep it from moving now lol :)

 

 

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phaedra Exonar wrote:


Innula Zenovka wrote:

Heavens above.. now we're back on the Server forum!

This is getting silly.

it's path finding for the forums, you need to set a post to "static post" to keep it from moving now lol
:)

 

 

In that case, I think the functions llFleeFrom and, for some people, llDeleteCharacter may come in very useful!

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That's actually really amusing :)

Anyway, whilst not strictly OT to the OP - here are my questions about pathfinding.

 

Why do we need to use another viewer to update (optmise) our parcel / regions?

Why do I now need to unlink buildings (remove the floor prim) to make it walkable?  This is especially pertinant as mesh builds can't simply be unlinked.  The only option (if I've read correctly) is to add another prim to act as the physics shape?! Or re-upload the mesh...

After applying a change to a fence as per the wikki - how long is it supposed to take to update the Navmesh?

Thanks

Black

 

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Glad you liked my little joke!    I'll try to answer your questions, but I'm by no means an expert in this -- I'm simply a landowner who's been trying to find out what to for the best with my sims, and how to do it, and a scripter who's been trying to find out how pathfinding is likely to affect what I do.    

I think at the moment you need the latest Beta viewer or the Project Viewer to do very much with optimising things because they are the only viewers with the new floaters (off the build menu) that you need to change things from being moveable obstacles into something else, or making areas walkable or whatever.    Niran's latest viewer may have them, too -- I've not looked yet, but certainly neither the official viewer nor any of the TPVs do.  

The reason, as I understand it, you need to start unlinking stuff  if you want to make parts of it walkable is that the NavMesh sees (or doesn't) entire linksets.   So it's not like texturing parts of the build with edit linked parts.   But I've not really explored that area in any detail.   So I'm not sure what happens if you set the whole building to being walkable -- presumably the creatures are going to know not to try to walk up the walls.    But I just don't know about that.    

Certainly the tool in the beta viewer you use for that simply gives you a list of objects (it looks a bit like the top scripts window in the Region/Estate tools, which you may have seen if you're a sim owner or estate manager).   

That why you have to unlink the doors-- much to my annoyance, I have to say -- if you want to make a building a "static obstacle".   If you leave the doors linked, they'll be static too, and that means that llSetRot and llSetPos stop working on them (and throw a script error if you try to touch the door to open it).   But I'm not all sure it makes a great deal of difference if you leave the door linked unless you particularly want pathfinding objects to be able to negotiate it.   I did a couple of tests with Npose and MLPV beds, and they don't seem to mind being turned into static obstacles, but I want to do some more testing before I commit myself on that.

When you've done something that affects the navmesh in a region, you get an extra button appear at the bottom of your screen, which you can click to to send the changes back to the Navmesh (so long as no one else is editing it).   Or you can leave it and changes will be sent back as and when the sim gets round to it.   It doesn't take very long at all.  

I found Inara Pey's articles on pathfinding very helpful as an introduction to the viewer tools and how they work.   And apparently the wiki articles are going to be revised shortly, which is good news since parts of them are badly in need of it.

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Thanks for the reply Innula - the reason I asked about the viewer is that LL have pushed pathfinding out (which therefore must be working more or less as intended) but not given an easy route to optismise parcel / regions which I guess is what LL would like us to do?

As for delinking things so they can be walked around - don't think I am going to bother as I prefer the lower land impact afforded by linksets since the introduction of the new prim accounting system.  In the future perhaps I'll create specific builds to take advantage of pathfinding but that is a way off for now.

There indeed was a button at the bottom of my screen labelled "Clean Region" ...  the button label was way to eh?! to risk pressing it (I had visions of things being returned so decided to leave it and will let the sim do whatever it needs to do in due course).

Heaing off now to look at the link.

Black

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So if Pathfinding is "ON" by default, on a shared Mainland SIM,instead of watching an army of Bots on a parcel, we'll be watching an army of scripted objects going around in circles.  This sound better everyday.

When I first heard about Pathfinding, I had thought this is really cool.

But the more I read of it's massive impact, the more I'm thinking that this was a very bad idea.

As far as informing Residents of the deploy goes, Only Linden Lab know how many hits (and hence about how many Residents) the Path Finding blog post got.

What should be on the Log In screen is a huge blurb saying "Path Finding Comes To Second Life." with links to information.

But once again LL does NOT know how to communicate (use it's own tools) with the general population of Second Life.

Mainly from what I see it is people with a vested interest in SL who check these Forums or even SLU.  Every one else mainly hears only second hand and often incomplete or inaccurate information if they hear anything at all.

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The button is now "Rebake Region".  I don't know if it used to be "Clean Region" but the one to press is certainly "Rebake Region".

I think, reading between the lines of Lorca Linden's reply to Nalates, they seem to want to get pathfinding rolled out onto the whole grid without anything too dreadful happening, and also make sure the tools in the beta viewer were working properly, before doing an official viewer with the tools.    At that point they''ll announce pathfinding is officially turned on, I think.  So that's why you need the beta viewer to optimise regions; pathfinding isn't really out of beta yet.    

It also, I guess, gives people who are interested a chance to familiarise themselves with the tools, so we can help people in the groups and forums and so forth.   By the time everyone starts using it, they'll be enough people in the building and scripting and viewer support groups who feel confident enough to answer questions.   I think we're going to see lots of conversations on the lines of 

-- "Why have all the doors in my house stopped working and started giving me error messages about pathfinding? Is it a known bug?" 

--"Did you just turn your whole house into a static obstacle with the new tools?"

--"Why yes, now you come to mention it...."

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According to Lorca Linden's reply to Nalates ,Perrie,


We do not consider pathfinding to be fully released until the pathfinding viewer tools are out of beta. This is why we have not yet made an official announcement. I agree that we need to do a pass on our pathfinding related wiki as some of the information there has not been updated since we were in alpha. We plan to make a blog post in the near future that will address some common misconceptions we have heard about pathfinding. We also plan to continue updating the “Good Building Practices” guide so that it will be a useful resource for Residents looking to make optimized content.


I don't particularly agree with the reasoning, but there will be an announcement shortly, it seems, once they're satisfied the viewer tools are working OK and they've given the wiki articles a much-needed update.

What is the massive impact it's supposed to have?  Everything I've read recently suggests the technical Lindens involved are saying that, under normal circumstances, the only things that are going to take a hit from pathfinding performance issues are pathfinding objects, but I've probably missed something.

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Ok I went to the path finding meeting yesterday on the beta grid and talked to Falcon and Lorca linden. Well I tried to anyway, for the most part they do not want to hear what we have to say unless we can document it and reproduce it in a jira. When I told them stuff was acting inconsistantly I was all but called a liar and that it can't happen. Then we were advised that it was not the proper place to discuss these issues. However when I asked them were the proper place was, I recieved no answer.

They did answer some of my questions though and I did find some stuff out.

For most of the issues people are having, especially with vehicles and other stuff is not really pathfinding. Its the new havoc engine they rolled out with path finding. It effects the script call llVolumeDetect which sets prims phantom yet physical. We have opened a JIRA on it if you wish to read more and vote on it.

https://jira.secondlife.com/browse/PATHBUG-181?focusedCommentId=338678

 

I also specifically asked what is meant by Optimizing a region for path finding. If it was needed if did not intend to run path findig characters on your sim. And if simply turning the feature off was good enough.

First of all, simply turning it off will not help if you have issues. Like I said before this only disable the abality to run characters in that region. Falcon suggested that you look at your sim stats to see if you are indeed having issues. If you are then it should be optimized. If you see no change then you probably don't need to mess with it.

The 18 percent or 4ms performance hit is mostly if you are running numerous path finding characters on a sim that is not optimized for it. And even they they said its very rare. They have been watching performance since it rolled out and it doesn't seem to be making much of a difference and they are not getting compliants about it. As much as I hate to admit it, our sim performance actually went up lol.

If you want to optimize your region you do need the beta pathfinding viewer and you can do a bulk change setting to the whole region. Here is the page that shows how.   http://wiki.secondlife.com/wiki/Universal_Attribute_Changes_for_Pathfinding


Falcon suggested using the setting to change unscripted items to static objects. you would type in   "update-pathfinding-objects region unscripted obstacle"

Keep in mind path finding does not see everything on the sim. So you may want to check some of it manually.

DO NOT choose "all obstacle" it will seriously screw up scripted items, especially if it moves, like cars and doors. Take my word for it, I learned the hard way. Thank god I did it on an almost empty sim lol.

They did also admit they are not done with project yet, but they felt is was good enough to roll out and get it started to see what would happen. And they are still working on tweaking the tools for the actaul vewer release.

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Innula

I'm going to take the second point first:

"it can't be to do with pathfinding?" Well, perhaps to a degree it isn't, but the basic error in traffic calculation was certainly introduced to server code around the time Pathfinding infected the Grid, and it certainly first surfaced as an issue on Magnum RC.  Guilt by association?

There is another aspect though, and this is more insidious: I suspect that as Pathfinding and Havok 7 was rolled to the Grid some aspects of sim operation were changed, maybe "reverted" in Lindenspeak.  It now seems that bots are being counted as genuine avatar visitors again.  That is definitely an aspect that is NOT "working as expected"...unless...I recall that back when Rod announced the advent of Pathfinding that "empty spaces" are not inviting.  So maybe there is an algorithm that is intended to count NPCs as vistors to give ranking in search to Pathfinding sims and this code also allows bots to be counted in seach ranking?  The sounds a tad Macchiavellian, but it's the best explanation I have for what is a very real issue, yet we are told all is "working as expected"

As regards the bandwidth issue I am a bit out of my depth here.  However this may be a consequence of sims that have little or no "spare time".  The connection has held on all the sims that I have seen this issue.  I had noticed in times past that these sims had very little on no spare time, so Havok 7 physics may well be causing this. 

Note I am not blaming Linden Lab for this, it is a consequence of the change that we were warned might occur.  I am old enough to recall the manifold issues that accompanied the introduction of Havok 4 to the Grid some years ago.

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I downloaded the latest project viewer this morning to have a look at path finding so the button label “Clean Region” was the one presented at the bottom of the screen.  I actually didn’t notice the button until I moved to another area on our mainland parcel.

 

That is a good point however about people changing linksets into static obstacles – I as a builder prefer not using rez boxes and the like, if using sculpts for instance I will try and make the sculpt fit my build without using scripts.  So the “static obstacle” setting might be an issue in the future…   The whole building process might be turned upside down thinking about how to make things walkable by NPC’s.

 

So, with baited breath we will wait until the tools are out of Beta and then see what happens but my first tentative steps have yielded positive results in so much as the beginning phase of optimising our parcel – I wonder what the impact will be though and whether other parcel owners in this region will update / optimise their parcels!

 

Update

Further to this morning’s post the Navmesh has been updated (according to the floater) and the changes I made on our parcel to individual objects have ‘stuck’ without me pressing anything – this pleases me as I certainly won’t have building rights on other parcels in this region.

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Ayesha Askham wrote:

Innula

I'm going to take the second point first:

"it can't be to do with pathfinding?" Well, perhaps to a degree it isn't, but the basic error in traffic calculation was certainly introduced to server code around the time Pathfinding infected the Grid, and it certainly first surfaced as an issue on Magnum RC.  Guilt by association?

There is another aspect though, and this is more insidious: I suspect that as Pathfinding and Havok 7 was rolled to the Grid some aspects of sim operation were changed, maybe "reverted" in Lindenspeak.  It now seems that bots are being counted as genuine avatar visitors again.  That is definitely an aspect that is NOT "working as expected"...unless...I recall that back when Rod announced the advent of Pathfinding that "empty spaces" are not inviting.  So maybe there is an algorithm that is intended to count NPCs as vistors to give ranking in search to Pathfinding sims and this code also allows bots to be counted in seach ranking?  The sounds a tad Machiavellian, but it's the best explanation I have for what is a very real issue, yet we are told all is "working as expected"

As regards the bandwidth issue I am a bit out of my depth here.  However this may be a consequence of sims that have little or no "spare time".  The connection has held on all the sims that I have seen this issue.  I had noticed in times past that these sims had very little on no spare time, so Havok 7 physics may well be causing this. 

Note I am not blaming Linden Lab for this, it is a consequence of the change that we were warned might occur.  I am old enough to recall the manifold issues that accompanied the introduction of Havok 4 to the Grid some years ago.

I'm sorry, but I don't see that makes much sense.   You might say "guilt by association" (never a sound principle, to my mind), but I'd rather say "post hoc ergo propter hoc"    

I just do not understand how some Machiavellian scheme by LL to count NPCs as characters would either involve allowing bots to be counted in search ranking (since bots aren't NPCs, they're avatars, and LL can only tell the difference between a bot and an avatar with a human driving it if you flag your bot as being one) or, more to the point, cause traffic ratings on busy sims suddenly to fall dramatically (which is what the problem is).   I can see how it might cause them to go up where they shouldn't, but not go down.    And I simply can't see why the problem, if it's caused by pathfinding, didn't become obvious before on the pathfinding beta sims or on the Magnum sims, which got the pathfinding code a week or so ago.

As to the bandwidth issue, it's just not one of which I'm aware.   How does it manifest itself?    Does it affect sims or the avatars on them, and what should I be looking at in the statistics window to know whether I am, or the sim I'm on is, experiencing it?

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I've been using the Beta Viewer, Second Life 3.4.0 (262596) Jul 27 2012 13:41:21 (Second Life Beta Viewer), which certainly says "Rebake Region" (I assume we're talking about the same thing):

rebake region.JPG

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Innula

Firstly I did not say that it MUST be to do with Pathfinding.  There was other code introduced alongside Pathfinding so it MIGHT have been that...I don't know.  All I DO know is that there are a lot of folk posting in a very responsible way to JIRA SVC-8099 about a serious negative change in traffic calculation, which appears to be inconsistent.  And I have seen it on a parcel that my partner manages, so I know it's not horse feathers. 

There will be many folk seeing things happening which are not to their liking and automatically blaming Pathfinding - I am NOT one of them.

The Bandwidth issue is something that I am less sure of.  You see the bandwidth in the Stats window below Viewer FPS.  Also, at least in my Firestorm there's the little bars up in the top right-hand corner that show packet-loss and bandwidth in various traffic-light colours: red is Bad!

I asume that a high bandwidth figure indicates a lot of data being downloaded to the viewer, since I see it regularly rise if I visit a sim for the first time after a cache clearance.

Why this bandwidth thing is worse I simply do not know, but as I say I am fairly sure it has to do with the amount of free-time (also in the stats window toward the bottom) a sim has. 

Although I have not been adversely affected by this, other than textures taking an age to rez..others say it causes huge amounts of client lag.

PS: The edit was to move a block of text from one paragraph  (where Lithium decided that I wanted it) to where I wanted it!!

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Update 11/08/2012

With the latest Beta Viewer from the downloads page, the wording for the button label is "Rebake", much clearer to understand.

So, I created a simple character using the new LL pathfinding functions and watched it merrily wander around - I won't be leaving the object out though as my simple 1 prim cube had a LE of 15!  Not sure if the LE values are going to tweaked - I do hope so as I feel that is way to costly.

Thanks for all your help Innula.

Black

 

Oh, now I can see the issue with the wording of the button label!  I downloaded "Second Life 3.3.3 (260597) Jun 26 2012 11:18:14 (Project Viewer - Pathfinding)" and not the Beta Viewer from the viewers page - will try that one later on :)

Black

Snapshot showing Clean up region.jpg

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