Wheel Rotation Issue

Unity Engine
1

I’m having a bit of an issue I can’t seem to resolve no matter what I do. The wheels are rotating locally as they should be (to make it appear the wheels are turning as the car accelerates). I am observing the transforms for the wheels with the issue and noticing every so many frames they are getting a 180- degree rotation in the Z axis. Basically as I accelerate they seem to be “flipping” around the Z axis. I have a hunch it’s this line of code

the variable aRight is a Vector3 “var aRight : Vector3;”

private var rotateAmount : Vector3;

function updateWheels()
{		

	// front wheels need rotating on their y axis too, for steering
	wheelT[0].localEulerAngles.y = horizontal * 30;
	wheelT[2].localEulerAngles.y = horizontal * 30;

	rotateAmount = aRight * (relativeVelocity.z * 1.7 * Time.deltaTime * Mathf.Rad2Deg);

	wheelT[0].Rotate(rotateAmount);
	wheelT[1].Rotate(rotateAmount);
	wheelT[2].Rotate(rotateAmount);
	wheelT[3].Rotate(rotateAmount);
}
2

SOLVED: Well I solved this issue and it’s not too hackish. Basically I realized the Euler Angle calculations for the steering effect (wheels turning around Y axis) was conflicting with the Rotate that was making the wheels rotate around X axis based on kart speed. I created parent gameobject transforms for the two front wheels, exposed them as public assignable variables and then just separated out the Euler Angle calculations on those parent transforms. Seems this separation worked like a charm. So my script function ended up smaller and like this:
"function updateWheels()
{

// front wheels need rotating based on speed
wheelT[0].transform.Rotate( relativeVelocity.z * 2, 0, 0);
wheelT[1].transform.Rotate( relativeVelocity.z * 2, 0, 0);
wheelT[2].transform.Rotate( relativeVelocity.z * 2, 0, 0);
wheelT[3].transform.Rotate( relativeVelocity.z * 2, 0, 0);

// front wheels need rotating on their y axis too, for steering
LFWheelTransform.localEulerAngles.y = horizontal * 40;
RFWheelTransform.localEulerAngles.y = horizontal * 40;
}

3

Glad you solved your issue :wink: looking at your code in the second post it looks like you are going to have 4 “transform” lookups every frame eg :

wheelT[0].transform.Rotate( relativeVelocity.z * 2, 0, 0);

I believe it would be better to cache the transforms themselves , perhaps in a different list or array or fields whatever to avoid this look up 4 times per frame per car.

4

another nano second optimization would be to create one Vector3 like this for the expression:

var wheelRotationVector:Vector3 = new Vector3(relativeVelocity.z * 2,0,0);
wheelTTransforms[0].Rotate( wheelRotationVector);
wheelTTransforms[1].Rotate( wheelRotationVector);
wheelTTransforms[2].Rotate( wheelRotationVector);
wheelTTransforms[3].Rotate( wheelRotationVector);

very small optimizations but i guess it doesn’t hurt to know

5

Thanks for the help. All optimizations are worth it :slight_smile: