Suspension arm

Questions & Answers
1

I hate 3dsMax, It screws up the pivots of objects and makes using them really difficult,

This should be easy to do but I can’t for the life of me figure it out, Hope someone can help.

My Car has a suspension arm which is attached to the wheel, I want to make the suspension arm travel up and down when the wheel bounces up and down.

I figured the way to do this is to put the pivot in the right place on the suspension arm, and then use a “look at” using the target as the wheel’s transform.

However, doing this, when the car goes up or down a slope, the object appears to “twist” - I figure I need to lock one of the axis’s of the look at - and here’s the question:

When I use LookAt - the object appears to completely disregard it’s children status, (it doesn’t add the cars heading or tilt to the look at equation.)

Is there another method I should use, I want a subject object suspension arm to move it’s pivot up and down based on the height of an attached wheel - but thats it, no fancy rotations or anything like that, just bounce up and down…

2

You can use LookAt, but you must specify the second parameter, worldUp. It’s a vector that defines the up side; if not specified, Unity assumes Vector3.up - that’s why the arm stays horizontal even when the vehicle is on a slope.

If the suspension arm is childed to the vehicle’s body, you can use this attached to the arm:

var wheel: Transform; // drag the wheel here

function Update(){
    transform.LookAt(wheel, transform.parent.transform.up);
}

If the arm isn’t a vehicle child, you can define the vehicle’s transform in a variable, like this:

var wheel: Transform; // drag the wheel here
var vehicle: Transform; // drag the vehicle's body here

function Update(){
    transform.LookAt(wheel, vehicle.up);
}

For this to work, the arm model Z axis must point to the wheel, and its pivot must be correctly set. If you have problems with this, create an empty game object, rotate it to have Z pointing to the wheel, then set its position at the correct point in the vehicle’s body. Attach the script to the game object, and child your arm model to it.