vehicle movement ceiling

The maximum height ceiling for physical vehicles is 4096m, while the maximum height for non-physical vehicles is 768m. Why the disparity?

Thanto, this relates because the regular build height for prims is capped at 768 m. However, if I'm not mistaken, I've seen some tricks used to surpass that limit too. It's been awhile since I've checked personally, so...

I'm moving this to Scripting Tips forum... anyone have any hints?

Hey Thantos,

If my sources are correct, the limits on build height are for two main reasons, one practical and one technical.

Practically speaking, it would be awfully easy to lose objects in space if there was no build altitude cap. A region simulating builds up to 768m (~0.5 mile) has 50 million cubic meters in which you can lose objects. Simulating up to 4096 (< 3 miles) gives you 268 million cubic meters. Imagine the waste and clutter on the server if the build limits were higher, or if any of those objects were poorly scripted and lagged things terribly. Not good.

The technical reason is that the objects inworld are stored with a given precision. As the numbers get bigger (e.g., with high altitude), the precision suffers (1, 2). In simple terms, imagine your object is at:

<128.000, 128.000, 25.000>

roughly the center of the sim at ground level. Then jack it way up in the sky. The data structure used to store each of the three numbers has only limited space to store the height (z) component, so it begins chopping decimals off one by one to make room for the bigger numbers:

<128.000, 128.000, 1000.000> 1000m (~2/3 mile) altitude

<128.000, 128.000, 10000.00> 10,000m

<128.000, 128.000, 100000.0> and so on

<128.000, 128.000, 1000000>

After awhile, the system is rounding off positions to the nearest meter or more, which will make your carefully, precisely positioned avatar bits or skybox start to look really bizarre.

The result is a simple cap that keeps your builds where you can find them and looking good.

What was the question again?

I'd speculate that the disparity between build and vehicle limits is because, practically, folks probably don't need buildings that are more than a half-mile high (768m). At some point, high is just high regardless if it is a half mile or ten miles. Nonphys vehicles conform to these rules because at a more technical level, they're not handled much differently than a stationary building is.

The speeds at which physical vehicles travel, though, may require more space. For example, a booster-assisted jet in SL can easily break 300 mph. At that speed, you'd hit the 768 ceiling in, what, six seconds? Not very much fun.

(Don't quote me, I'm probably completely wrong. )

There are a few problems with the aforementioned explanations. One is that large physical objects can push themselves ridiculously high (from what others have said, there's no limit, and people have gone upwards of 100km up), and they can keep themselves at that level through various means. Additionally, physical objects can be made non-physical, at which point there's no longer a need to push themselves up (though I'm not sure what happens to the object if it's about 768m). I asked in Linden Answers, because I wanted such issues dealt with also. It seems silly and entirely arbitrary to me to allow physical objects to be lost in space, but not non-physical objects. If there is some reason, I'm sure the Lindens would know.

One thing I'd probably rectify...I don't think a non-physical vehicle can go above the prim height cap, though I have not tested this yet as I've only just now started delving into this 'cookie jar' of almost limitless prims.

I do know that you can push a physical object well above the 768m as I've sat and watched a friend shoot of gigantic rockets that report their position at an interval...and the last he got was above 4k, and my vehicles seem to act normally when I fly just above skyboxes that everyone loves to put at the build height cap.

Now, I have seen builds that were up higher than this, and I've managed to get something to stay up rediculously high as well. The problem was as soon as I tried to edit something, it dropped everything in the linkset I was messing with down to 768.

Sure, there are workarounds and loopholes in most any complex system like SL.