Sphere cast problem

Unity Engine
1

I am having problems with sphere cast.

I am using it to move a sphere across a scene, and if it hits a box collider move it to that location.

The problem I am having is that I can end up inside objects. This only happens when I am moving quickly (when gravityAmount is high.)

I have checked that I am not starting from within the object but I still hit the ‘Bad News’ debug line.

The problem is intermittent and I cannot replicate it everytime so the Time.deltaTime variable is possibly playing a part.

Any help would be vey welcome.

void UpdateFalling ()
	{
                int layerMask = 1 << 8;

                //gravityAmount is a class variable (float)
		gravityAmount = Mathf.Min (maxGravityAmount, gravityAmount + (Time.deltaTime * gravitySmooth));
		
		RaycastHit hitInfo;
		
		if (Physics.SphereCast(transform.position, 20.0f, gravityVector, 
			out hitInfo, gravityAmount, layerMask))
		{
			//Do something with hitInfo
		}
		else
		{
                        //We can move to the position
			transform.position = transform.position + (gravityAmount * gravityVector);

                        //Check we have not somehow collided.
                        if (Physics.CheckSphere(transform.position, 20.0f, layerMask))
                        {
                                 Debug.LogError("Bad news");
                        }
		}
	}
2

Are you calling UpdateFalling from FixedUpdate? Physics code should use FixedUpdate rather than Update.

3

Thanks Sajidfarooq, I tried this but I’m afraid it did not help.

As I understand it, you need to use FixedUpdate when using RigidBodies and applying forces.

I don’t have a rigidbody attached to to either object involved.

It does seem to only happen if the object being collided with is moving though, but I didn’t think it was possible for another object to move during an method.

4

When I use Custom collision detection i write my own update methods.

public Awake()
{ 
     StartCoroutine(CoUpdate() );
}
public IEnumerator CoUpdate()
{ 
    while(true)
    {
          //Check Sphere Cast here
          yield return new WaitForSeconds(0.001f); // The faster the better for collision.. should help to never miss. 
    }
}

Even better idea… Make the WaitForSeconds based on how fast the player is traveling… So it can be dynamic checking…

5

Thanks Ereous. Any chance that you can explain why you need to do this so I can better understand why it’s solving my problem.

Is it just a case of making the update happen more frequently so raising the chance of catching a collision?

6

I do this for better control. Since I program in C# it allows me to halt updating if I want by simply added in a bool before hand…

if(haltUpdate)
yield return null;

But also as you stated you can control how fast something reacts as well.