Issue with x axis flipped on vehicle

[Pindrought]

In the jolt vehicle constraint test, I have modified the code for generating the wheel settings to easily identify which wheels were which. I just changed the position to be offset differently for the X for one side on the front & back.

     // Wheels
    WheelSettingsWV *w1 = new WheelSettingsWV;
    w1->mPosition = Vec3(half_vehicle_width * 2, -0.9f * half_vehicle_height, half_vehicle_length - 2.0f * wheel_radius);
    w1->mMaxSteerAngle = max_steering_angle;
    w1->mMaxHandBrakeTorque = 0.0f; // Front wheel doesn't have hand brake

    WheelSettingsWV *w2 = new WheelSettingsWV;
    w2->mPosition = Vec3(-half_vehicle_width, -0.9f * half_vehicle_height, half_vehicle_length - 2.0f * wheel_radius);
    w2->mMaxSteerAngle = max_steering_angle;
    w2->mMaxHandBrakeTorque = 0.0f; // Front wheel doesn't have hand brake

    WheelSettingsWV *w3 = new WheelSettingsWV;
    w3->mPosition = Vec3(half_vehicle_width * 2, -0.9f * half_vehicle_height, -half_vehicle_length + 2.0f * wheel_radius);
    w3->mMaxSteerAngle = 0.0f;

    WheelSettingsWV *w4 = new WheelSettingsWV;
    w4->mPosition = Vec3(-half_vehicle_width, -0.9f * half_vehicle_height, -half_vehicle_length + 2.0f * wheel_radius);
    w4->mMaxSteerAngle = 0.0f;

I have attached an image showing a comparison between my engine and jolt's vehicle test. The first thing i'm confused about is why is the x axis flipped (In the jolt test)?

The wheels with a negative x are on the right and the wheels with a positive x are on the left (In the Jolt test).

I am also having the issue of in my engine where since the x axis is flipped (in comparison to the jolt test), my wheels turn the wrong way.

I know I can just reverse what I am passing into for the right value into controller->SetDriverInput but I wanted to see what the alternatives are and if there is some setting I should be changing. I was also concerned that if the wheels are meant to turn at different speeds based on how far they are turned that this would cause issues to just reverse the -right instead of fixing the problem at hand.

Thank you.

[jrouwe]

SetDriverInput with inRight = 1 is supposed to steer to the right, so there's definitively something wrong.

How have you configured VehicleConstraintSettings::mUp and VehicleConstraintSettings::mForward? By default Z is forward and Y is up. Jolt uses a right handed coordinate system so X must be left. So that's why the left wheel has positive X and the right wheel negative X. If your X axis is flipped, you're probably using a left handed coordinate system which is also valid, but not the one Jolt is using.

Can you confirm which axis points in which direction in your engine?

[Pindrought]

I am using a left handed coordinate system in my engine so positive x points to the right and positive z is forward and positive y is up. I am constructing my perspective matrix with the XMMatrixPerspectiveFovLH function from DirectX.

For my VehicleConstraintSettings, I am using the default mUp of {0, 1, 0} and the default m_Forward of {0, 0, 1}

Since I am using a left handed coordinate system, would the correct approach just be for me to reverse the inRight value that I am passing to SetDriverInput or should I be approaching this a different way?

Thanks so much for taking the time to respond.

[jrouwe]

I think that should work, but I am wondering what other issues you may run into (it's hard for me to oversee every place where I made the right handed assumption). Another possible fix is to flip the x axis on every transform you send to Jolt and again on the way back.

[Pindrought]

Okay thank you so much for the reply and for the physics library. The code and samples are great. I am going to think on this today. It might make more sense for me to just adjust my engine to use right handed coordinates instead so that it aligns with Jolt.