Pathfinding Q&A

[BlackMagi Darkwatch]

Another question about Exclusion Volumes (EV)

I created an EV for a building out of prims, positioned, linked – prims used = 6 (LI 3, physics shape Convex Hull). Tested the path using the floater from inside the building to the outside, no problems at all. Tried the same exercise but this time using a single mesh and then hit a bit of a wall.

The mesh shown in the linkset window was bracketed as concave and there was no option in the drop down list to turn it into an EV as physics type prim.  However, upon changing the physics type to convex hull (as we’ve been told there is no agent interaction with an EV) I was then able to select EV from the drop down list in the linksets floater.  Rebaked the navmesh and then tested – there was no way to place the test character within the building and upon inspecting the object it had turned itself phantom.  Not sure if this is a bug or expected behaviour but it would be very nice to have the option to create a 1LI EV for people who would like to use pathfinding. What does the concave bit mean?

 

Thank you

Black

[Darrius Gothly]

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Innula Zenovka wrote:

I honestly don't know.   According to this

transcript from 2007

, back then the sim took a snapshot once an hour, but that was five years ago.   Things might have changed since.   ... [snip]

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(ToffT) I sell a product that rezzes a fairly large number of prims .. once .. then sits idle forevermore. On more than one occassion both the device and all the prims it rezzes have vanished after a restart. Usually, but not always, once it has sat for at least 24 hours then it is still present after restart. However if a restart occurs anytime within that first 24 hours, the chances of it vanishing are VERY high. It's also not a No Copy item, it is Copy/Mod so it's simple to replace. However the annoyance factor is quite high.

[Perrie Juran]

Thank you Innula

I had read about the snapshots being taken also before the restarts.  And I refrain from rezzing no copy items on the days they are doing restarts.

Like so many things that are Second Life, we all live with a degree of uncertainty.  It's frsutrating when you get caught by a 'glitch.'

Like you, everything in my Intan is legitimate.  But what's thirty or forty dollars to Linden Lab? 

Over the years Inventory Back Up has been requested multiple times.  What the problem is in providing this is a puzzle, especially when considering that obviously the systems that are in place do fail from time to time. 

But that is a whole other topic.

https://jira.secondlife.com/secure/IssueNavigator.jspa?

https://jira.secondlife.com/browse/VWR-3796

https://jira.secondlife.com/browse/SVC-4304

[Falcon Linden]

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BlackMagi Darkwatch wrote:

Another question about Exclusion Volumes (EV)

I created an EV for a building out of prims, positioned, linked – prims used = 6 (LI 3, physics shape Convex Hull). Tested the path using the floater from inside the building to the outside, no problems at all. Tried the same exercise but this time using a single mesh and then hit a bit of a wall.

The mesh shown in the linkset window was bracketed as concave and there was no option in the drop down list to turn it into an EV as physics type prim.  However, upon changing the physics type to convex hull (as we’ve been told there is no agent interaction with an EV) I was then able to select EV from the drop down list in the linksets floater.  Rebaked the navmesh and then tested – there was no way to place the test character within the building and upon inspecting the object it had turned itself phantom.  Not sure if this is a bug or expected behaviour but it would be very nice to have the option to create a 1LI EV for people who would like to use pathfinding. What does the concave bit mean?

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Great questions. 

1) Exclusion volumes are, by definition, "volumes". They must be made up of one or more well-defined volumetric shapes (e.g., boxes, spheres, cylinders, convex hulls, etc.). Meshes, on the other thand, are composed of individual triangles generally do not represent convex shapes (if you're using a mesh to represent a convex shape, don't. Use a convex hull instead). Essentially, for a mesh object, we don't have a good way of determining "inside" from "outside" without some very expensive calculations (and, in many cases, there is no "inside" vs "outside" because the mesh doesn't form what mathematicians call a "closed, orientable surface"). So if we were to let you designate a mesh as an EV what you'd end up with is an object where each individual triangle behaves like a 2D exclusion volume (e.g., by slicing the navmesh where they intersect) which is definitely not the idea. The same thing applies to Material Phantoms.

One workaround might be to upload the mesh using a convex decomposition for physics and leave it as shape type prim. The result would be a shape made up of one or more convex hulls, but still representing the original mesh fairly accurately. To be clear, I've never tested this as it wasn't really expected to be a common use case, so if you try it, please report back.

2) Exclusion volumes and material phantoms are always phantom. The idea is that they should be used to designate volumes in a region which have different properties (e.g., EVs designate volumes characters can't enter and material phantoms designate volumes where characters may move at different speeds). Designating an entire house as an exclusion volume doesn't make much sense. Perhaps what you want to do in this case is set the house to Static Obstacle? That will prevent it from being included in the navmesh but will allow it to behave normally in the physics system.

3) Yes, LI 1 exclusion/material volumes would be nice. It was an idea we discussed internally but determined that it had too many implications. To ensure that the low land impact was only applied to objects that were being used exclusively as exclusion/material volumes (rather than allowing a new exploit for getting any linkset down to 1 LI) and that that land impact accurately reflected resources consumed on the server, we would have had to make EVs/MVs into a new kind of "first class object" (like Linden Trees, Prims, etc.). This, in turn, would have introduced significant UI work and under-the-hood complexity.

 

Hope that helps,

Falcon

[Vladi Hazelnut]

I never said they called me a liar, read my post. I said "I was all but called a liar and told that it can't happen" When they got uppity and said its been out and we should have been testing I got a little ruffled since we have been testing and working with them. Feeding them information, showing them snapshots and even making video. The truth of the matter is things we tested got the opposite results when it rolled out grid wide than they did during testing (only two days before I might add). They duplicated our sim on the beta grid just so we could perform such tests. We also tested in the pathfinding sandboxes on the magnum server.

On two instances during the meeting I was told what I said couldn't happen. I am not mentally handicapped, I saw what I saw as did the owner of the sim who was testing with me. We worked weeks days and hours coming up with a fix for the problems this would have on our sim and products. And then when it rolled out grid wide it reacted differently and we had to scramble to figure it out.

And not only that, when it first rolled our cars and track worked ok. Other sims were having problems. 4 to 5 hours laters all of a sudden our sim starts doing the same. That is just messed up right there. And this was not after a restart or anything, just out of the blue.

Then when I try to discuss these issues I am told its not the right place? Was this not a pathfinding meeting? As for reproducing the problems, some of them we can, easily all they have to do is come watch a demostration. Obviously telling them about it isn't enough because they don't believe us. As for things acting differently after the roll out, that one is kind of hard to prove isn't. Unles I take video of every test I do. Which is what I should do in the future. But then again why waste my hard drive space when they just dismiss it anyway.

Am I upset, you bet I am. If you thought that was not civilized you might want to know I was really holding back.

[Syn Short]

 

Support for regions with any sorta path-finding turned off is not available.

Reason why:  It causes crashes.  ( a known problem )

 

 

[Perrie Juran]

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Syn Short wrote:

 

Support for regions with any sorta path-finding turned off is not available.

Reason why:  It causes crashes.  ( a known problem )

 

 

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Was this an "Official Answer" you got to a support request?