Vehicle Buoyancy

First this is setting the vehicle parameters, this is different from llSetBuoyancy, that's not being set.

Is something really not right with vehicle buoyancy? I set an object physical, set it to be a balloon, shut off hovering (time scale = 1000), shut off all the motors (start time scale = 1000), and friction (time scale = 1000).

If I set the vehicle buoyancy = 1 it takes off for the stratosphere. It seems like a neutral value is about .37 or so.

Is that really correct or am I missing something?

That really is how Vehicle Buoyancy behaves, in my experience. Usually for my vehicles, a buoyancy value of 0.95 or so seems to be approximately neutral... in your case, 0.37 seems pretty severe, so maybe some other force is involved.

For at least one project I've done, I actually disabled vehicle buoyancy and turned on llSetBuoyancy, which didn't have this problem. Despite the warnings not to mix physics functions, it worked just fine. You might want to try it. Just be sure they're not both on at the same time!

Hmmmph, thanks very much Lex.

I've wondered if the actual value is related to the object's mass. For my latest vehicle, a setting of about 0.92 had a mostly neutral buoyancy. But it would still creep upwards after a while... I never emperically nailed down the exact figure, as while my craft is gravity-neutral it should always be in motion and this isn't a big concern.

Good idea on using normal buoyancy, but I wonder if there is a difference in how energy is used. In other words, a slow moving vehicle using llSetBuoyancy() wouldn't notice a large amount of energy drain, but a fast vehicle might. I'm not entirely clear on the relationships between prim energy and the vehicle system. (Seems to be closely related, just like using the impulse system to drive an object.)

I think maybe the problems with vehicle buoyancy might be an issue of a difference between an object's prim-center and its center of mass. In other words, if something's lopsided, the vehicle system might not deal with it properly.

As to energy, the vehicle system is completely exempt from energy, but llSetBuoyancy isn't. So if your object is too heavy for llSetBuoyancy to handle, then you're kinda stuck with the wonky vehicle buoyancy.