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Vehicle physics engine going haywire on simcrossings

Judith Flow

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Since maybe a week, I noticed the physics engine of vehicles regularly go haywire on simcrossings. The effect is very inconsistent regarding both what happens and when it happens.

What I've experienced so far:

  • vehicles going into a random spin
  • vehicles completely stop moving
  • airplanes plummeting down to the ground
  • vehicle orientation changes (switching left and right, or forward turns into up, etc.)
  • The vehicles ALWAYS stop responding to any user input, whether it's directional or attempting to turn the engine on or off.

These are NOT the usual lag effects we've seen in the past. Instead, these effects seem to change the behaviour of vehicles themselves or their script on simcrossing. I haven't found any pattern for these occurances either. One moment, crossing from sim A into sim B goes perfectly, 3 minutes later, going from that same sim A into that same sim B crashes the vehicle in one of the ways described above. It's completely possible to see someone in front of you pass without trouble, while you get hit with this new "feature" yourself. I've also noticed it happens with vehicles from different creators. Some I know to script their own planes, of others I have no idea whether they script themselves or use standard or 3rd party vehicle scripts. I have spoken to a few other residents who encountered similar problems, I just haven't found anything online about this "new feature" yet.

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Hi  Judith  Merry Xmas:)

There are  many different factors that can determine  your sim crossing experience while flying  sl aircraft

I fly every day in a varity of sims private islands,mainland , and Blake sea region....and  yes sim crossings can be a little crazy  sometimes.  But  this is "normal" behavior  i.e  nothing has  gone wrong in the last  few server updates.

Keyboard Control is always lost during a sim crossing  its just a question of for how long...it varies.

Some things you can do to make it as painless as possible:

1. Slow  down  before crossing

2  Avoid being in a turn while  sim crossing....fly straight into the next sim without banking.

3. Avoid crossing in Sim corners...or  into diagonal  sim.

4 Expect  bad sim crossing if either sim has lots of Avatars and  activity

5. Dont touch  the controls once you enter the next sim...wait until you can visually see that control is restored  (the View       will do a small jerk when control is back)

6.  yes...they never fixed the problem with your camera sometimes  looking backwards after  the next sim server takes over........just "tap"  the left or right  turn  key  and the cam view will be back to looking forward.

7. Fly above 100 meters elevation when passing over unknow parcels. (to avoid ban lines).

8 Buy a hud navigation Aid  to "see" and avoid ban lines,full  parcels,no object entry etc  before you get there

9.  Your PC,graphics card, Viewer, internet connection, wi fi  and the condition of the Sim/parcel  you are entering are all important factors

Good flying  for you !  Happy Holidays  to all !

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You're fully right Judith, something changed, maybe 2 months ago.

(like a new physic engine maybe, because even ground vehicles don't react exactly the same than before)

I noticed all the bad effects that you mentioned.

However, all planes are not affected the same way.

Some crossings are able to "kill" the script, then your plane falls like a stone.

Crossings always were touchy, but this kind of bug didn't exist in the past. It was more a problem to recover the control.


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I have experienced this too, but it's been intermittent, rare, and I haven't been able to reproduce it.

I make and use boats quite a bit in SL and have done so since 2007; these bizzare haywire problems on sim crossings are definitely new. Past two months or maybe a bit earlier.

It's a physics problem (specifically a vehicle parameters problem I think), and in my experience, the script itself is still functioning but the physics is completely messed up.

Example - driving a boat from one sim to the next, after the crossing it drops like a rock till it hits the ground level. The script is still working, the control event is still firing, as evidenced by the rudder turning left and right in response to the arrow keys, and the forward/back keys still trigger the motor sounds and particle effects. The boat is still physical, and obviously still effected by sim 'gravity' since it fell till it hit the ground. But the vehicle parameters all seem to have failed. The boat no longer hovers at the set height above water, and the linear and angular motors are not working as it no longer moves in response to controls.


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I ran into an aircraft now that seems to cross fine so far. Sure, it still occasionally has the old fashioned bugs on sim crossings, but on successful crossings, the physics of the vehicle at least seem persistent instead of going haywire.

I'm not sure how the builder (MeganAnn Mills) did this exactly, but she did tell me she scripted some kind of physics reset into her script which triggers on every sim crossing to circumvent the problem. So far it seems to work, I haven't experienced a single physics mess up in her plane so far.

But, while I'm glad that she seemed able to built a fix into her script, it does mean a piece of code is triggered on every single crossing, which is undesirable from a resource-efficiency point of view. Crossings should simply work without having to run a redundant bit of code every time.

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Myself and others have been helping a few Lindens with this particular issue. Whilst they have confirmed they can recreate the problem with the vehicles I gave them, I'm having to look to work in some work around into the scripts myself and a friend worked on until LL finally get it fixed.

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For freezes

Besides reistting, a script can be put in a vehicle to check the physics state and set it back to true. A few hints at that are obvious, use coordinate get functions and figure the edge and then start checking if it is true or false and set it right. So, looking into:


For rubber banding and maybe spinning.

Maybe turning off velocity or ping interpolation may help, it is in the devlope menu. More info here: http://wiki.secondlife.com/wiki/Develop_menu and it basically says, turn off Velocity Interpolation for rubber banding. I think maybe spinning or diving may work better to.


Ctrl+Shift+1 may help to understand what may be occuring and figure out if it is a bug directly effecting veihicles OR just something else that in turn causes cars issues.
 This window doesn't show when you are in mouselook. Mouselook is another way to reduce lag a bit, or it used to be. It may tax your GPU less.  I have seen just shrinking the screen down (or changing the resolution with the settings you find for monitors in control panel) helps with GPU speed and if the whole system is running quicker some of these issues may be fixed or eased a bit. But, it sounds like network issues and the velocity interpolation issue.

But, if the creator made a lower lag plane it may also be helping a bit by helping the SL client run as quick as it can. SO, I thoguht it may be worth mentioning reducing GPU lag.

Mainland driving is so terrible sometimes it is hard to tell if it is bugs or just sims that need restarting or are full of laggy items. Scripts sometimes build up and sims end up being restarted by track managers/owners so I know from the racing tracks that mainland sims, even if you do not cross sims, are maybe not the best places to drive. Not bashing mainland, it has many other benifits and I do drive mainland now and then myself for some sims. IN fact, I am on my way to do just that lol.

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That was my ticket on jira.

Now I've had a bit more time to work on this issue, I have found that during my testing the aircraft I made goes spazzy during a sim crossing is still showing it's physics as "ON" according to a monitoring script.

If I "stop" and "Start" the main engine script whilst still seated on the aircraft, it proceeds to continue spazzing out.  If I unsit and then sit on the vehicle again, it works normally until the next sim crossing that spazzes it.


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