Balloons

I know there are several people with balloons out there, someone must've noticed these things before..

Specifically, I'm noticing weird things with
llSetVehicleFloatParam(VEHICLE_HOVER_HEIGHT, hoverHeight);

1) This seems to top out at 100m global height. (Why?) Surely not all balloons are limited to 100m, there must be a better way than using the hover height that I have not uncovered.

2) When I increase my hover height, it also imparts forward velocity to my craft. I took out all calls to VEHICLE_LINEAR_MOTOR_DIRECTION to be sure that my script wasn't accidentally causing this, and it still happened.


I've looked in the script library, and there's no balloon script in there to peek at, unfortunately. Anyone have any tips for success with balloons?

Yeah, it's limited to 100 meters. Not sure why. You can cheat slightly by making it track against land height instead of global height, which will let you always clear mountains and such, but then your balloon will bounce all over the place.

Most people, instead, set a neutral bouyancy and just use a linear motor on the Z axis to move up or down.

I believe vehicles are effected by wind, could this be causing the movement you see? If so, you could set the linear motor to <0.0, 0.0, 0.0> to put the breaks on.

I've encountered the same thing, Wednesday, trying to build a hover-vehicle of some sort, a while back. Anytime I would try to change the hoverheight, the vehicle would surge forward or backwards, depending on... well, some random thing. I kinda gave up on vehicles at that point.

Ah! I tried using the z component of the linear motor to raise/lower my vehicle, but had problems with it going in other directions in addition to straight up. Maybe I should re-visit that method and clamp the vehicle so it can't move its local z axis off of straight up and down. Thanks, Reitsuki.


Wednesday, if it was just the effect of the wind, I would expect to see the movements all the time, not specifically limited to when I change the hover height.

Unexplained forward or backward movement when you are trying to move a vehicle vertically or horizontally is almost always due to VEHICLE_LINEAR_DEFLECTION_*. This is especially true if you are using something other than the linear motor to move the vehicle.

Less linear deflection (higher timescale and/or lower efficiency) will cause this behavior to lessen. At the same time if you rely on linear deflection to keep the craft aloft (if it's a standard hover vehicle, you should be using 1.0 buoyancy and no linear deflection), then the craft will tend to float or fall downward.

The vehicle parameters we have at our disposal interact with each other in many subtle ways. Learn them all and you can weave your own magical web of behaviors. Or something.

Some of the most fun balloons are not vehicles at all!

Toss the following in state_entry():
llSetBuoyancy(1.0);

...and you have an instant balloon. Add a little more sophistication and you have my drifter balloon script (public domain, available upon request).

Ah, beautiful, the LINEAR_DEFLECTION parameters solved the problem of skewing forward/backward when i try to go up or down. One problem solved!

Tried following Reitsuki's advice about using the linear z motor to go up and down instead of the hover height, with bad results. For some reason the vehicle really wants to hover exactly 7m above current ground level. This is very puzzling to me; I have no HOVER parameters set anywhere. When I pass an x value to the linear motor I get a noticeable response with relatively low numbers, for example, a 1 will set me moving forward. But changing the z does almost nothing -- pumping it up to 50 or so will cause a very slight movement upward (about 2.5m). I wondered if it was remembering parameters from a previous version of the script, so I added hover parameters to make it hover 100m up -- worked fine. Removed the hover statements, went right back down to 7m.