// Called once per physics update
void FixedUpdate()
{
//Raycast down along the suspension to find out how far the ground is to the wheel
if (Physics.Raycast(new Ray(_dummyWheel.position, -_dummyWheel.up), out _hit, groundDetectorDistance, groundLayers)) //The wheel is in contact with the ground
{
if (!_isGrounded) //If not previously grounded, set the prevPosition value to the wheel's current position.
{
_prevPosition = _dummyWheel.position;
}
_isGrounded = true;
}
else //The wheel is in the air
{
_isGrounded = false;
}
//Set steering angle of the wheel dummy
_dummyWheel.localEulerAngles = new Vector3(0, _wheelSteerAngle, 0);
//Calculate the wheel's rotation given it's angular velocity
_wheelRotationAngle += _wheelAngularVelocity * Time.deltaTime;
//Set the rotation and steer angle of the wheel model
this.transform.localEulerAngles = new Vector3(_wheelRotationAngle, _wheelSteerAngle, 0);
//Apply rolling force to tires if they are grounded and don't have motor torque applied to them.
if (_isGrounded && _wheelMotorTorque == 0)
{
//Apply angular force to wheel from slip
_wheelAngularVelocity -= Mathf.Sign(_forwardSlip) * _forwardFriction.Evaluate(_forwardSlip) / (Mathf.PI * 2.0f * radius) / mass * Time.deltaTime;
}
//Apply motor torque
_wheelAngularVelocity += _wheelMotorTorque / radius / mass * Time.deltaTime;
//Apply brake torque
_wheelAngularVelocity -= Mathf.Sign(_wheelAngularVelocity) * Mathf.Min(Mathf.Abs(_wheelAngularVelocity), _wheelBrakeTorque * radius / mass * Time.deltaTime);
if (_isGrounded && parentRigidbody != null)
{
//Calculate the wheel's linear velocity
Vector3 velocity = (transform.position - _prevPosition) / Time.fixedDeltaTime;
_prevPosition = transform.position;
//Store the forward and sideways direction to improve performance
Vector3 forward = _dummyWheel.forward;
Vector3 sideways = -_dummyWheel.right;
//Calculate the forward and sideways velocity components relative to the wheel
Vector3 forwardVelocity = Vector3.Dot(velocity, forward) * forward;
Vector3 sidewaysVelocity = Vector3.Dot(velocity, sideways) * sideways;
//Calculate the slip velocities. Note that these values are different from the standard slip calculation.
_forwardSlip = -Mathf.Sign(Vector3.Dot(forward, forwardVelocity)) * forwardVelocity.magnitude + (_wheelAngularVelocity * Mathf.PI / 180.0f * radius);
_sidewaysSlip = -Mathf.Sign(Vector3.Dot(sideways, sidewaysVelocity)) * sidewaysVelocity.magnitude;
//Forward slip force
_totalForce = _dummyWheel.forward * Mathf.Sign(_forwardSlip) * _forwardFriction.Evaluate(_forwardSlip);
//Lateral slip force
_totalForce -= _dummyWheel.right * Mathf.Sign(_sidewaysSlip) * _forwardFriction.Evaluate(_sidewaysSlip);
parentRigidbody.AddForceAtPosition(_totalForce, transform.position);
}
}
