Unity 5: Now the ball from the first tutorial rolls itself

After a longer absence from touching Unity I just tried the good old Roll-a-ball tutorial project as a small refresh in Unity 5. Unfortunately, as soon as the function AddForce() on the rigidbody component is used (even with no data from the input) the ball starts to roll away in +Z direction after about 8 seconds when I start game mode.

It's just a script with a the usual MonoBehavior class and FixedUpdate:

Code (CSharp):

1.  
2. void FixedUpdate() {
3.        Vector3 movement = new Vector3(0.0f, 0.0f, 0.0f);
4.        GetComponent<Rigidbody>().AddForce(movement);
5. }
6.  

I also tried the tutorial in Unity 4 and there the ball sticks correctly at its original position.

Any idea?

Thanks,
Robbson

 

This might be related to the physx upgrade.

You're constantly doing something with the rigidbody so it is never set to sleep mode, after a while floating point errors get large enough to move the ball. I've had a similar problem, it can be solved by only calling addforce when you actually have a force to add.

 

Yes, probably it's a floating point issue. But if you use debug output of all the related values you still see plain 0.0 values. I would expect rather some very small values like in the transform component.

It seems to be working when I add if(movement != Vector3.zero) before AddForce().
Maybe it's catching invalid values or something.

But still 0.0 should be an reliable value, especially when nothing is added.
If there are some problems to be expected it should be mentioned in the tutorial.

 

I have the same problem, but can't get it to work. Could you share the script that is working for version 5? Thanks!

 

@gerdw
As I wrote, you just insert the addtional if-statement:

Code (CSharp):

1.  
2. if( movement != Vector3.zero) {
3.     GetComponent<Rigidbody>().AddForce(movement);
4. }
5.  

 

You should not call GetComponent<Rigidbody>()every frame though!

 

Of course not... but for the sake of a basic tutorial it's ok.

 

I still keep getting message to fix errors. This is the script:


using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour {

public float speed;

void FixedUpdate()
{
float moveHorizontal = Input.GetAxis ("Horizontal");
float moveVertical = Input.GetAxis ("Vertical");

Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

if( movement != Vector3.zero) {
GetComponent<Rigidbody>().AddForce(movement * speed * Time.deltaTime);
}
{

 

You have some mangled braces in your script gerdw. You should have something like (indents really help to know what you are missing ):

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class PlayerController : MonoBehaviour {
5.  
6.   public float speed;
7.  
8.   void FixedUpdate()
9.   {
10.     float moveHorizontal = Input.GetAxis ("Horizontal");
11.     float moveVertical = Input.GetAxis ("Vertical");
12.    
13.     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
14.    
15.     if( movement != Vector3.zero) {
16.       GetComponent<Rigidbody>().AddForce(movement * speed * Time.deltaTime);
17.     }
18.   }
19. }

 

thanks for the tip. This is what I have right now, but the ball is still moving up and down, while it should lie still on the ground...

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.    
4. public class PlayerController : MonoBehaviour {
5.        
6.     public float speed;
7.     public Rigidbody rb;
8.    
9.     void Start()
10.     {
11.         rb = GetComponent<Rigidbody>();
12.     }
13.  
14.     void FixedUpdate()
15.     {
16.         float moveHorizontal = Input.GetAxis ("Horizontal");
17.         float moveVertical = Input.GetAxis ("Vertical");
18.  
19.         Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
20.  
21.         if (movement != Vector3.zero) {
22.             rb.AddForce (movement * speed * Time.deltaTime);
23.         }
24.     }
25. }

 

Do you have a controller connected? It could be stuck giving 0.05 vertical input for example.

 

No, there is no controller connected. I am working on a MacBook without any external controllers.

 

You might want to submit a bug report then.