Detetecting collision or trigger between instantiated objects

Unity Engine
1

I have watched a bunch of tutorials about this and read the manual concerning onCollisionEnter and onTriggerEnter, however I still can’t figure out what should be a very straightforward task.

All I want is to detect when two instantiated objects touch each other and add a point to the score.

Both objects have rigid bodys, one is kinematic because I don’t want physics to move it. I am detecting for both onCollisionEnter and onTriggerEnter because I really don’t know which one I should be using here.

This is the code I have. I have it attached to the camera. When I play the game, no matter how many spheres contact the target and bounce off, the points variable never changes.

public int points = 0;

void OnCollisionEnter(Collision col)
{
   points += 1;
}
void OnTriggerEnter(Collider other)
{
   points += 1;
}

void Update()
{
   //create sphere
   GameObject sphere = GameObject.CreatePrimitive (PrimitiveType.Sphere);
   //add a rigidbody
   Rigidbody spheresRigidBody = sphere.AddComponent<Rigidbody> ();
   //here I calculate a vector 3 and use AddForce to shoot the sphere,
   //I am using a rigid body and an AddForce because I want the sphere
   //to arc in a natural way effected by physics
   //to keep this short I won't include all that

   //create target
   GameObject target = GameObject.CreatePrimitive(PrimitiveType.Cylinder);
   //add rigid body and make kinematic (don't want target falling)
   Rigidbody targetRigidBody = target.AddComponent<Rigidbody> ();
   targetRigidBody.isKinematic = true;
}
2

You should add an if statement that asks if the two collide a point shall be added so it would be like:

void OnTriggerEnter(Collider other)
{
     if(gameObject.tag == Your object)
{
      gameObject.Active (false);
      points += 1;
}
}

This is how I do it in my code :slight_smile:

P.S. I shouldn’t add it to you Camera as the camera has nothing to do with it.
Make an empty gameobject and attach it to that but thats just what I would do :smile:

1 Like
3

Thanks JobR!

I don’t have any of the objects tagged. Do I have to add a tag to make this work?

Also, why change the object to not active?

4

Forgot to mention make sure both the object have colliders and the target is a trigger

5

It’s just the way I do it and think is the most easiest so you can choose if you want to use the tagging :slight_smile:

So it isn’t on the screen anymore and can’t be picked up 1 again but you can delete that part if you want to have it all the time in the scene

6

I don’t understand. If I don’t want to use tagging, then what would I put in the if statement?

Also, changing isTrigger = true on the target results in the spheres passing right through. I’d like to keep them bouncing off if they hit. Does that mean I’ll have to use OnCollisionEnter?

7

If you don’t want to use tagging you should declare a variable for the target and put that in.
If you want to let them bounce well I don’t know how to keep that going as OnTriggerEnter and OnCollisionEnter means that if they enter something happens so sorry :frowning:

1 Like
8

You have to put OnCollisionEnter() on the target. So you have to add a script component too if you want to create the target dynamically.

1 Like
9

JobR - that’s ok, I really do appreciate your help!

Fraconte - Ok, I’ve never done that before. Would I create a new separate script with OnCollision Enter() in it?

like:

targetColScript:

using UnityEngine;
using System.Collections;

public class targetColScript : MonoBehaviour
{
   void OnCollisionEnter(Collision col)
   {
     points += 1;
   }
}

and then attach this script to target by using:

target.gameObject.AddComponent<targetColScript> ();

I tired doing that but get the error:
Assets/targetColScript.cs(8,17): error CS0103: The name `points’ does not exist in the current context

Thanks for helping this dumb noob!

10

Don’t quit everyone needs to learn why it doesn’t work is because there is no variable called points

1 Like
11

“points” was declared in the first script. If I declare it again in targetColScript, won’t it be a different variable then? So then there will be 2 global variables named “points”?

12

Did you declare your first script in the second one?

13

No, how would I go about doing that?

14

Ok, I figured out one way to make it work, not sure if it’s the best way or not. I simply declared points in the first script as a global static…

public static int points = 0;

…and then put this in the second script:

void OnCollisionEnter(Collision col)
{
     firstScript.points += 1;
}

The only other question I have is how can I test to make sure that the collision is between the sphere and the target? I would assume that if one sphere collided with another sphere that OnCollisionEnter() would still fire and +1 points, which I don’t want.

15

OnCollisionEnter (Collision col) detects all (and only) the collisions involving the gameObject who owns the script. If other objects can hit your target, you can check the Collision parameter (i.e.: col.gameObject.name or col.gameObject.tag).

1 Like
16

Thanks, guys.