Jumping when I alter land

[Cully Andel]

We just bought  some mainland. When I alter the land to make it level parts of it seem to be 'unstable' If you stand on it you jsut jump around all over the place. I've tried clicking the button that comes up at the bottom requesting region rebake, but it's still the same. Been tested on 2 diferent viewers so I know it's not that.

 

I will send a ticket but any thoughts on this? (Please note I'm not technically minded so has to be simple English)

[Qwalyphi Korpov]

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Cully Andel wrote:

We just bought  some mainland. When I alter the land to make it level parts of it seem to be 'unstable' If you stand on it you jsut jump around all over the place. I've tried clicking the button that comes up at the bottom requesting region rebake, but it's still the same. Been tested on 2 diferent viewers so I know it's not that.

 

I will send a ticket but any thoughts on this? (Please note I'm not technically minded so has to be simple English)

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My recollection on this is that after the next region restart things will settle down.   It's happened to me also with various viewers.

[UncommonTruth]

I'm not exactly sure what you mean by jumping around... but did you smooth it after you raised/lowered? 

[Medhue Simoni]

Ok, I'll just mention some unique properties of mainland sims. Mainland has limits on how far you can alter the height of the land. I think it is +/- 10 meters from their set default. This might have something to do with the jumping. Maybe you are near the limit.

Rebaking a sim, as far as I know, only rebakes the Navmesh of the sim. So, basically, if you move items or change the land height, you would rebake to have the Navmesh reflect the changes. Navmesh is the collision mesh for pathfinding objects.

[Qwalyphi Korpov]

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UncommonTruth wrote:

I'm not exactly sure what you mean by jumping around... but did you smooth it after you raised/lowered? 

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I can get this to happen if I lower an area and then step into it.  Sometimes I "float" as if the ground was unchanged.  Sometimes I drop into the lowered area and bounce up and down... like what happens if you fly into an area with ban lines and then stop flying.  You drop down to about 80 meters and bounce around.   I think a server restart resolves all that.

[Qwalyphi Korpov]

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Medhue Simoni wrote:

Ok, I'll just mention some unique properties of mainland sims. Mainland has limits on how far you can alter the height of the land. I think it is +/- 10 meters from their set default. This might have something to do with the jumping. Maybe you are near the limit.

Rebaking a sim, as far as I know, only rebakes the Navmesh of the sim. So, basically, if you move items or change the land height, you would rebake to have the Navmesh reflect the changes. Navmesh is the collision mesh for pathfinding objects.

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Tiny correction - the typical mainland limit is +/- 4 meters.   The bouncy effect isn't related to that limit afaik.  It's how the AV/viewer interacts with the terrain.  I don't really have any understanding of specifically what is out of sync causing the bounces.

[Eisenkreuz]

The problem with you jumping around is the sim still thinks the land is at the previous level. No need to file a ticket. Simply just rebake the region, and the problem will clear up for you. If you are using the SL viewer, the rebake Region option is under the BUILD>Pathfinding menu.

 

 

[Qwalyphi Korpov]

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Eisenkreuz wrote:

The problem with you jumping around is the sim still thinks the land is at the previous level. No need to file a ticket. Simply just rebake the region, and the problem will clear up for you. If you are using the SL viewer, the rebake Region option is under the BUILD>Pathfinding menu.

 

 

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Please note that the use of rebake region was mentioned as not helping in the initial post.

[Tamara Artis]

The answer is simple, move few steps away and don't change the land right below your feets;) you can fly around, sit on some chair or something...

[Andrew Linden]

I can explain why the avatar bounces when you raise the terrain under its feet:

The terrain info is stored in two formats:  (1) a 2D array of floating point heights (a "heightfield") that is used for visualization and (2) a big list of triangles (a "mesh") which is used fo collision purposes.  Whenever you modify the terrain you are actually changing the heightfield data (1), which then must be translated into mesh form (2) before you avatar can collide with it.  The conversion to mesh is computationally expensive and can take a significant amount of time to complete.  To reduce lag caused by the mesh calculation the simulator employs two strategies (a) it waits several seconds after the last terrain modification just in case the person editing it is going to make another change (no need to compute the mesh if it is about to change again) and (b) it performs the mesh calculation on a separate thread, which allows the simulator to continue moving things along in the meantime.

The mesh format was added to help optimize the physics engine.  It is faster than a heightfield shape for collisions in general and most ray-trace events, however the benefits of going to mesh did not outweigh the work required to get it done... until we added the pathfinding characters.  The performance improvements for computing paths over a mesh shape is much much better than doing the same for a heightfield collision shape, hence the work was done.

So, when you make a change to the terrain it can take several seconds for the collision shape to update, but why does the avatar bounce?

There is special code in the simulator that checks to see if your avatar is under the terrain.  If it finds this to be true then it will lift your avatar to the surface.  Unfortunately the code that performs the underground check is still using the heightfield data rather than the mesh data.  The way to fix it would probably be to perform a ray-trace up against the terrain mesh from the avatar's feet and then if the ray hits the terrain we'd know the avatar's feet were actually below the mesh.

In the meantime... don't stand where you're raising the terrain.

[Ciaran Laval]

As an aside, why do we need an under the terrain feature? I'm thinking along the lines of tunnels, underground railways, roleplaying dungeons etc. I've been wondering about flattening my land and building a mesh terrain, but that would take time I currently don't have.

[Qwalyphi Korpov]

Wow.  Thanks for that explanation.

[Jenni Darkwatch]

Might be a safeguard? Don't know. In game engines it's sometimes done to avoid chars from going "offworld" and becoming corrupted. Though I'd think a simple "if you're below 0m, move to 0m" would fix that.

[Ciaran Laval]

Yup I've had items go offworld in the past, so there is a need for detecting when something has gone offworld. Maybe it's to do with the physics engine not being a fan of hollows.