OnCollisionEnter/Exit and Collider edges.

Questions & Answers
1

Hello everyone,

I have a project in which when you click on an object you select it. When selected, the object follows the mouse cursor. Now I want to have the selected object jump on top of any other objects that I point my mouse on. Here is my piece of code that controls the mouse movement and object collision detection.

public bool isSelected;

public List<Collider> currentlyCollidingWith = new List<Collider>();
	public GameObject lastCollidedObject;

	void OnCollisionEnter(Collision col){
		currentlyCollidingWith.Add(col.collider);
		lastCollidedObject=col.gameObject;
	}

	void OnCollisionExit(Collision col){
		currentlyCollidingWith.Remove(col.collider);
	}
void OnMouseDown(){
		isSelected=!isSelected;
	}

void FixedUpdate(){
		if(isSelected)
		{
			Vector3 distanceToCam = Camera.main.WorldToScreenPoint(transform.position);
			Vector3 mousePos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x,Input.mousePosition.y,distanceToCam.z));
			if(currentlyCollidingWith.Count>0)
			{
				transform.position=new Vector3(mousePos.x,lastCollidedObject.collider.bounds.max.y+gameObject.collider.bounds.extents.y,mousePos.z);
			}
			else
			{
				transform.position=new Vector3(mousePos.x,gameObject.collider.bounds.extents.y,mousePos.z);
			}
			if(Input.GetKeyUp(KeyCode.Mouse1))
			{
				transform.RotateAround(new Vector3(transform.position.x,transform.position.y,transform.position.z),new Vector3(0,1,0),45.0f);

			}
		}
	}

Also you can see my problem on this video as well:

The problem occurs only when an object’s collider touches the edge of another collider. On such occasions, the collider returns a collision on one frame but no collision on the next frame which causes the object to change positions every frame.

Any help is appreciated. Thank you.

2

Have you tried using OnCollisionStay() as that is called every frame that a collider is inside or touching another.

OnCollisionEnter() is only called on the frame where to colliders touch so in the next frame if there is still a collision the collider has not enterd or exited so CollisionEnter and Exit are not called.

Here is a link to the documentaion