RC-Car-Sim throttle/acceleration issue

Getting Started
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6

Thanks alot :blush:

I kinda fixed it, or atleast it drives ok now and this is how the suspension looks while driving:

Iam honestly not really sure why it works now. I switched back to the approach with the accelerationPoint and change the CG as @CodeSmile recommend in the settings of the Rigidbody. Before that I changed the values in my script before. I also noticed that my AddForceAtPosition points for my lateral grip where wrong and maybe that also messed with the weight transfer, but I honestly don’t know. Thats my changes:

// Throttle

private void ApplyThrottle(Transform tireTransformFront, Transform tireTransformRear, bool v)
{
    RaycastHit hit;

    Vector3 frontRayOrigin = tireTransformFront.position;
    Vector3 rearRayOrigin = tireTransformRear.position;

    Vector3 frontRayDir = -tireTransformFront.up;
    Vector3 rearRayDir = -tireTransformRear.up;

    RaycastHit frontHit;
    RaycastHit rearHit;

    bool frontRayDidHit = Physics.Raycast(frontRayOrigin, frontRayDir, out frontHit, frontRaycastLength, groundLayer);
    bool rearRayDidHit = Physics.Raycast(rearRayOrigin, rearRayDir, out rearHit, rearRaycastLength, groundLayer);

    bool rayDidHit = frontRayDidHit || rearRayDidHit;

    if (rayDidHit)
    {
        float throttleInput = Mathf.Max(0f, thbrInput);

        Vector3 forwardDir = carTransform.forward;

        float carForwardSpeed = Vector3.Dot(forwardDir, carRigidBody.linearVelocity);

        carVelocityRatio = Mathf.Clamp01(Mathf.Abs(carForwardSpeed) / maxSpeed);

        float motorTorqueCurve = powerCurve.Evaluate(carVelocityRatio);

        float throttle = (throttleInput * motorTorque * motorTorqueCurve);

        //carRigidBody.AddForce(carTransform.forward * throttle, ForceMode.Force);
        //carRigidBody.AddForceAtPosition(carTransform.forward * throttle, frontAccelerationPoint.position, ForceMode.Force);
        carRigidBody.AddForceAtPosition(carTransform.forward * throttle, rearAccelerationPoint.position, ForceMode.Force);

    }
}

// Brake / Drag Brake

private void ApplyBrake(Transform tireTransformFront, Transform tireTransformRear, bool v)
{
    RaycastHit hit;

    Vector3 frontRayOrigin = tireTransformFront.position;
    Vector3 rearRayOrigin = tireTransformRear.position;

    Vector3 frontRayDir = -tireTransformFront.up;
    Vector3 rearRayDir = -tireTransformRear.up;

    RaycastHit frontHit;
    RaycastHit rearHit;

    bool frontrayDidHit = Physics.Raycast(frontRayOrigin, frontRayDir, out frontHit, frontRaycastLength, groundLayer);
    bool rearrayDidHit = Physics.Raycast(rearRayOrigin, rearRayDir, out rearHit, rearRaycastLength, groundLayer);

    bool rayDidHit = frontrayDidHit || rearrayDidHit;

    float forwardSpeed = Vector3.Dot(carRigidBody.linearVelocity, carTransform.forward);

    if (rayDidHit)
    {
        if (forwardSpeed > 0f)
        {
            float brakeInput = MathF.Abs(Mathf.Min(0f, thbrInput));

            Vector3 brakeVec = -carTransform.forward;

            carVelocityRatio = Mathf.Clamp01(Mathf.Abs(forwardSpeed) / maxSpeed);

            float brakeForceCurve = brakeCurve.Evaluate(carVelocityRatio);

            float brake = (brakeInput * brakeForce * brakeForceCurve);

            //carRigidBody.AddForce(-carTransform.forward * brake, ForceMode.Force);

            //carRigidBody.AddForceAtPosition(-carTransform.forward * brake, frontAccelerationPoint.position, ForceMode.Force);
            carRigidBody.AddForceAtPosition(-carTransform.forward * brake, rearAccelerationPoint.position, ForceMode.Force);

            // Drag Brake

            if (Mathf.Abs(thbrInput) < 0.05f && rayDidHit)
            {
                //carRigidBody.AddForce(-carTransform.forward * dragBrake, ForceMode.Force);
                //carRigidBody.AddForceAtPosition(-carTransform.forward * dragBrake, frontAccelerationPoint.position, ForceMode.Force);
                carRigidBody.AddForceAtPosition(-carTransform.forward * dragBrake, rearAccelerationPoint.position, ForceMode.Force);
            }

        }
    }
}

I outsourced throttle and brake form the suspension function. I copied and pasted the rayDidHit stuff I used before and applied it to throttle and brake.

And my fixedUpdate:

for (int i = 0; i < tireTransformFront.Length; i++)
{
    Transform front = tireTransformFront[i];
    Transform rear = tireTransformRear[i];

    ApplyThrottle(front, rear, true);
}

for (int i = 0; i < tireTransformFront.Length; i++)
{
    Transform front = tireTransformFront[i];
    Transform rear = tireTransformRear[i];

    ApplyBrake(front, rear, true);
}

ChatGPT came up with this and I dont really understand why I needed to write the code like this and couldnt just call the function.

Thats a good idea to do that with a force. I tried to do that with changing grip levels:

float frontGripDownforceMultiplier = frontDownforceCurve.Evaluate(carVelocityRatio);
float frontGripRatio = (frontGrip * frontGripMultiplier) + (frontDownforceCoefficient * frontGripDownforceMultiplier);

Thanks! I will try that too.