How do i test whether my box collider is touching the floor or not?

Questions & Answers
1

I have a script that makes my car drive but i really cant figure out how to test if my box collider is grounded so i can stop it from moving forwards in the “Z” axis whilst in mid air.

Here Is My Script:

public var CarGravity : float = -20;
private var accel : Vector3;
public var throttle : float;
private var deadZone : float = .001;
private var myRight : Vector3;
private var velo : Vector3;
private var flatVelo : Vector3;
private var relativeVelocity : Vector3;
private var dir: Vector3;
private var flatDir : Vector3;
private var carUp : Vector3;
private var carTransform : Transform;
private var carRigidbody : Rigidbody;
private var engineForce : Vector3;
 
private var turnVec : Vector3;
private var imp : Vector3;
private var rev : float;
private var actualTurn : float;
private var carMass : float;
private var wheelTransform : Transform[] = new Transform[4];
public var actualGrip : float;
public var horizontal : float;
private var maxSpeedToTurn : float = .2;
 
public var frontLeftWheel : Transform;
public var frontRightWheel : Transform;
public var rearLeftWheel : Transform;
public var rearRightWheel : Transform;
 
public var LFWheelTransform : Transform;
public var RFWheelTransform : Transform;
 
public var power : float = 300;
public var maxSpeed : float = 50;
public var carGrip : float = 70;
public var turnSpeed : float = 3.0;
 
private var slideSpeed : float;
public var mySpeed : float;
 
private var carRight : Vector3;
private var carFwd : Vector3;
private var tempVEC : Vector3;
 
function Start()
{
    Initialize();
    Physics.gravity.y = CarGravity;
}
 
function Initialize()
{
    carTransform = transform;
    carRigidbody = rigidbody;
    carUp = carTransform.up;
    carMass = rigidbody.mass;
    carFwd = Vector3.forward;
    carRight = Vector3.down;
    setUpWheels();
    carRigidbody.centerOfMass = Vector3(0,-0.7,.35);
}
 
function Update()
{
    checkInput();
    carPhysicsUpdate();
}
 
function LateUpdate()
{
    rotateVisualWheels();
    engineSound();
}
 
function setUpWheels()
{
    if((null == frontLeftWheel || null == frontRightWheel || null == rearLeftWheel || null == rearRightWheel ))
    {
       Debug.LogError("One or more of the wheel transformshave not been plugged in on the car");
       Debug.Break();
    }
    else
    {
       wheelTransform[0] = frontLeftWheel;
       wheelTransform[1] = rearLeftWheel;
       wheelTransform[2] = frontRightWheel;
       wheelTransform[3] = rearRightWheel;
    }
}
 
private var rotationAmount : Vector3;
 
function rotateVisualWheels()
{
    LFWheelTransform.localEulerAngles.y = horizontal * 30;
    RFWheelTransform.localEulerAngles.y = horizontal * 30;
 
    rotationAmount = carRight * (relativeVelocity.z * 1.6 * Time.deltaTime * Mathf.Rad2Deg);
 
    wheelTransform[0].Rotate(rotationAmount);
    wheelTransform[1].Rotate(rotationAmount);
    wheelTransform[2].Rotate(rotationAmount);
    wheelTransform[3].Rotate(rotationAmount);
}
 
private var deviceAccelerometerSensitivity : float = 2;
 
function checkInput()
{
    if (Application.platform == RuntimePlatform.IPhonePlayer ||(Application.platform == RuntimePlatform.Android))
    {
       accel = Input.acceleration * deviceAccelerometerSensitivity;
 
       if(accel.x > deadZone || accel.x < -deadZone)
    {
       horizontal = accel.x;
    }
    else
    {
       horizontal = 0;
    }
       throttle =0;
 
       for (var touch : Touch in Input.touches)
    {
       if(touch.position.x > Screen.width -Screen.width/3 && touch.position.y < Screen.height/3)
       {
         throttle = 1;
       }
       else if(touch.position.x < Screen.width -Screen.width/3 && touch.position.y > Screen.height/3)
       {
         throttle= -1;
       }
    }
}
    else if (Application.platform == RuntimePlatform.WindowsEditor || RuntimePlatform.WindowsWebPlayer || RuntimePlatform.WindowsPlayer )
    {
       horizontal = Input.GetAxis("Horizontal");
       throttle = Input.GetAxis("Vertical");
    }
}
 
function carPhysicsUpdate()
{
    myRight = carTransform.right;
    velo = carRigidbody.velocity;
    tempVEC = Vector3(velo.x,0,velo.z);
    flatVelo = tempVEC;
    dir = transform.TransformDirection(carFwd);
    tempVEC = Vector3(dir.x,0,dir.z);
    flatDir = Vector3.Normalize(tempVEC);
    relativeVelocity = carTransform.InverseTransformDirection(flatVelo);
    slideSpeed = Vector3.Dot(myRight,flatVelo);
    mySpeed = flatVelo.magnitude;
    rev = Mathf.Sign(Vector3.Dot(flatVelo,flatDir));
    engineForce = ( flatDir * ( power * throttle ) * carMass);
    actualTurn = horizontal;
    if(rev < 0.1f)
    {
       actualTurn =- actualTurn;
    }
    turnVec =((( carUp * turnSpeed ) * actualTurn ) * carMass )* 800;
    actualGrip = Mathf.Lerp(100, carGrip, mySpeed * 0.02);
    imp = myRight * ( -slideSpeed * carMass * actualGrip);
}
 
function slowVelocity()
{
    carRigidbody.AddForce(-flatVelo * 0.8);
}
 
function engineSound()
{
    audio.pitch = 0.30 + mySpeed * 0.025;
    if (mySpeed > 30)
    {
       audio.pitch = 0.25 + mySpeed * 0.015;
    }
    if (mySpeed > 40)
    {
       audio.pitch = 0.20 + mySpeed * 0.013;
    }
    if (mySpeed > 49)
    {
       audio.pitch = 0.15 + mySpeed * 0.011;
    }
    if ( audio.pitch > 2.0 )
    {
       audio.pitch = 2.0;
    }
}
 
function FixedUpdate()
{
    if(mySpeed < maxSpeed)
    {
    carRigidbody.AddForce( engineForce * Time.deltaTime);
 
    if (mySpeed > maxSpeedToTurn)
    {
    carRigidbody.AddTorque ( turnVec * Time.deltaTime);
    }
    else if(mySpeed < maxSpeedToTurn)
    {
       return;
    }
    carRigidbody.AddForce( imp * Time.deltaTime );
    }
}
2

Sorry if this is wrong =) , you could try this, but for this to work you would have to tag the terrain with a tag called “Terrain”, you can use a different tag just remember to change the code!.

function OnCollisionEnter(collision : Collision) {
        if(collision.gameObject.tag == "Terrain"){
                print("The object is colliding with the floor!");
        }
}
3

you may also include something with oncollisionstay to make shure your car is grounded.
if you only include on collision enter your car will only get information on it being in contact with terrain for only one frame so you should also include oncollisionstay.