Facing some issues trying to set up a vehicle with Z+ as up.

[D8H]

GDevelop uses Z+ as up to be better integrated with the 2D engine that uses X and Y. I tried to modify the Wheeled Vehicle Controller Demo to set Z+ as up, but I couldn't make it work.

Do you see any issue with the way I set up the engine?

Untouched demo (Y+ is up)

Branch with logs:

• main...D8H:JoltPhysics.js:add-logs

The logged distance on Y between the car center and the wheel contact with the ground is a bit more than 0.8 as expected:
halfVehicleHeight + suspensionMinLength + wheelRadius = 0.2 + 0.3 + 0.3
The contacts rectangle is from (-0.85, -1.4) to (0.95, 1.4) which is expected according to halfVehicleWidth and wheelOffsetHorizontal.

Car center
0.000 -3.157 25.000
Wheel contacts
-0.852 -4.000 23.600
0.948 -4.000 23.600
-0.852 -4.000 26.400
0.948 -4.000 26.400

Modified demo (Z+ is up)

Branch with changes:

• main...D8H:JoltPhysics.js:test-car-on-z

Changes:

• Set vehicle and wheels up to: (0, 0, 1) and forward to: (1, 0, 0)
• Set wheels positions accordingly
• Override vehicle gravity to (0, 0, -9.8)
• Explicitly set the up for the collision tester
• Use the raycast tester (because I couldn't get contact with the other 2)
• Rotate the tracks
• Rotate to car to face the same direction relatively to the track

Result:

• The car body is lying on the ground
• When pressing W key, the wheels rotate but the car doesn't move
• When pressing A or D, the wheels doesn't seem to turn (but I only see 2 of them so I'm not sure).
• I'm not sure the wheels are rendered where they really are (so I relied on logs)

The logged distance on Z between the car center and the wheel contacts is about 0.2 which is probably the halfVehicleHeight as if there weren't any wheel.
The contacts rectangle is from (-0.91, -1.4) to (1.06, 1.4) which is kind of expected I guess.

Car center
0.023 -10.000 -13.807
Wheel contacts
1.081 -8.600 -14.000
-0.891 -8.600 -14.009
1.081 -11.400 -14.000
-0.891 -11.400 -14.009

[jrouwe]

I took a quick look and don't immediately see what's wrong. I know that it is possible to have a car with Z-up because I've done it. I need a bit of time to debug this.

[jrouwe]

You can control the wheel orientation, suspension direction and steering axis separately, so you have to change:

wheelS.mWheelUp = new Jolt.Vec3(0, 0, 1);
wheelS.mWheelForward = new Jolt.Vec3(1, 0, 0);

to:

wheelS.mWheelUp = new Jolt.Vec3(0, 0, 1);
wheelS.mWheelForward = new Jolt.Vec3(1, 0, 0);
wheelS.mSuspensionDirection = new Jolt.Vec3(0, 0, -1);
wheelS.mSteeringAxis = new Jolt.Vec3(0, 0, 1);

and then it works as intended. This can be used to give your wheels camber or toe or to give the suspension a caster angle.

So the whole sample becomes this:

vehicle_wheeled.zip

[D8H]

Thank you, it works like a charm!