Ground Vehicle contact points

I am working on a SimObject of type GroundVehicle:


And it is a LARGE vehicle - it is a NASA crawler transporter, measuring 131 feet long and 114 feet wide.

The problem I have is, when it is moving over UNEVEN ground, its tracks (extreme ends) go up and down off the ground. The reason for that is, the sim calculates the normal vector to the ground of its CENTERPOINT, and adjusts the pitch and roll of the object. This isn’t the problem for small vehicles like cars or trucks, but large vehicles will have their extreme parts larger than the terrain mesh grid point span, so while the object’s center may be over a certain terrain point altitude, its part that is far away from the centerpoint may “hang” in the air or embed into the ground.

This would be fixed if, as it is the case with Aircraft type object, GroundVehicle had the ability to define individual contact points in the format:

point.1 = param, param, param…
point.2 = param, param, param…

point.n = param, param, param…

With that, I could define 4 points where tracks are, and the model would be then properly placed on the ground. But it doesn’t.

Is there anything that can be done about this? So far, I’ve been going through my options:

  • Flatten the ground where the vehicle moves. This works, but then introduces other problems, like creating unrealistic “throughs”
  • Use SimConnect to set pitch and yaw to zero, so that the terrain is not a factor in setting the vehicle attitude. This however, will still cause tracks to hang in the air or get embedded in the ground over uneven terrain.
  • Create the vehicle as an Aircraft object. Probably the best way to go - but I am unsure about all the rest of the parameters and files that I can cull and remove to make this vehicle a very very simple airplane.

Can anyone suggest the best option for this?

Terrabuilder Team

Interesting situation, I doubt that anyone at MSFS has imagined this need, I don’t think they can give you a solution.

One possible approach is to create each boogie as independent simobject with their own contact point, then have them work relatedly in a hierarchy with the platform.

I think it would even be similar to how that thing should work in real life, right?

Don’t ask me how this would be done or if it’s possible, I have no idea, I’m just suggesting a conceptual approach.


Hi, thanks for chiming in! You are correct, the 4 bogeys are indeed pivoting in pitch and yaw, and they move up and down on massive hydraulic pistons - that’s how they get to level the platform when it goes up a launch platform incline. So - with this in mind, I attempted to define the SimObject as an Aircraft, not a GroundVehicle. This way, I can then give bogeys all the properties of the landing gears, including damping shock absorbers. I have to then redesign the model to include bogeys animating up and down on the hydraulic pistons.

So before I went too deep into this, I wanted to test if the waypoint flight plan would work properly. I gave this a go using a simple aircraft flight model from the samples, however this presents a new problem. I am not very good with Aircraft flight modeling and all the parameters. I changed a few parameters (like reference speeds) and I got the plane to move really slow (2 kts), but when I add a waypoint flightplan to it (Through SimConnect), it starts taking off right away, even at 2 kts. Completely unrealistic. I am not sure if the waypoint system can be used to taxi on the ground. It is really strange, if I give the same flightplan with waypoints to a GroundVehicle, it sticks to it precisely, but with Aircraft, it just takes off and ingores it. All the waypoint altitudes are specified as 0 AGL.

*** EDIT ***
I just looked into this and it is a known ASOBO bug that aircraft ignore the ground taxy waypoints. So - my approach to use Aircraft suspension system will have to wait till this is fixed. In the meantime, I will experiment with suppressing roll and pitch on the GroundVehicle SimObject - see if that gets me anywhere.

TerraBuilder Team


Thank you for your feedback!

These are all known issues, and some rework on the ground collision system is in our wish list. Hope it will be done sooner rather than later.

Have a good day,

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Hi Andrey,

Thanks for your reply. I actually managed to fix it somewhat, by using a flatten polygon (terraformer). I tried that before and it looks like I played with its height, and it was leaving deep troughs.

I tried again, but this time I didn’t adjust its height - I just left it as created. This actually flattened the area nicely without any steps on its edges. The movement of the vehicle is MUCH smoother, although it still has a few small snaps here and there, but they are quite acceptable.

TerraBuilder Team

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