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Bouncing Car

Daniel

Daniel

Messages
139
Country
netherlands
I have created a car, my first model created from scratch for FSX. So far I've succeeded in creating rotating wheels, working brake lights, head/tail lights during night (optionally during dusk and dawn too).

I'm stuck with one annoying issue. When the car is moving around (either after giving it a series of waypoints or by using AI DESIRED SPEED) it bounces every now and then.

From what I've been able to find on the web, it could be related to the static_cg_height and contact points, yet, unlike the aircraft.cfg you cannot set contactpoints in the sim.cfg file.

The car in Gmax has its wheels at the surface, but in FSX the wheels would sink into the ground and the bottom of the car would be on the ground. I then raised the car by increasing the static_cg_height (and as soon as the wheels where above the surface the car started casting a shadow as well)... but now it bounces.

If anyone could shed some light on this...

Thanks,

Daniel
 
I don't know the answer... but how about a workaround.

Make the model itself higher from the 0,0 point.. (put a box under it). See if the same thing happens.
 
Hi Folks

Denial said:
unlike the aircraft.cfg you cannot set contactpoints in the sim.cfg file.
Click to expand...

Daniel -
Have a look at the R22.
It uses a sim.cfg
and has contact points.

Try replicating from that.

Also should be details in the SDK.

EDIT -
SDK sim.cfg section doesn't mention proper contact points.

Try the Robbie anyway.
Set the points initially with a couple of m vertical offset,
that should give a clear indication whether they have any effect.

HTH
ATB
Paul
 
Last edited:
Daniel,

The "bouncing car" effect is caused by the rate which FSX updates data about the altitude of the land underneath it (i.e., as the ground height underneath the car is updated, the car is moved to that new altitude if you set its OnGround property to True). This makes the car look like it is bouncing.

SP1 reduced this side effect somewhat, but it's still there. You can reduce the effect further by turning down some complexity (so that the mesh updates are quicker.)

It's most prominent on areas of ground that are hilly (obviously). I bet if you place your car out in the desert or on a runway and drive it around (or have the game AI drive it for you) you won't notice it bouncing much.

In some of the missions I've designed that use cars, this was an unfortunate side effect ... but it probably has nothing to do with your design.

Cheers,
Kevin Greene
 
Thanks for all of your replies.

The car is actually driving on taxiways, but indeed it seemed to happen more often when I used waypoints with onground set to true. I now just set desired heading and speed. I also notice it in some add-on aircraft (when I'm taxiing or standing at a gate). Slow mesh updates on my rather old system sounds plausible.

I suppose I could always 'Freeze Altitude' if it gets too annoying :)

Daniel
 
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