How to prevent colliders from passing through each other?

Question

I am having trouble keeping game objects inside of a contained space. When they reach the edge, there is some momentary push back but then they will go right through the wal

Answer 1

1.) Never use MESH COLLIDER. Use combination of box and capsule collider.

2.) Check constraints in RigidBody. If you tick Freeze Position X than it will pass through the object on the X axis. (Same for y axis).

Answer 2

I have a pinball prototype that also gave me much trouble in the same areas. These are all the steps I've taken to almost (but not yet entirely) solve these problems:

For fast moving objects:

• Set the rigidbody's Interpolate to 'Interpolate' (this does not affect the actual physics simulation, but updates the rendering of the object properly - use this only on important objects from a rendering point of view, like the player, or a pinball, but not for projectiles)

• Set Collision Detection to Continuous Dynamic

• Attach the script DontGoThroughThings (https://www.auto.tuwien.ac.at/wordpress/?p=260) to your object. This script cleverly uses the Raycasting solution I posted in my other answer to pull back offending objects to before the collision points.

In Edit -> Project Settings -> Physics:

• Set Min Penetration for Penalty to a very low value. I've set mine to 0.001

• Set Solver Iteration Count to a higher value. I've set mine to 50, but you can probably do ok with much less.

All that is going to have a penalty in performace, but that's unavoidable. The defaults values are soft on performance but are not really intented for proper simulation of small and fast-moving objects.

Answer 3

Old Question but maybe it helps someone.

Go to Project settings > Time and Try dividing the fixed timestep and maximum allowed timestep by two or by four.

I had the problem that my player was able to squeeze through openings smaller than the players collider and that solved it. It also helps with stopping fast moving objects.

Answer 4

Collision with fast-moving objects is always a problem. A good way to ensure that you detect all collision is to use Raycasting instead of relying on the physics simulation. This works well for bullets or small objects, but will not produce good results for large objects. http://unity3d.com/support/documentation/ScriptReference/Physics.Raycast.html

Pseudo-codeish (I don't have code-completion here and a poor memory):

void FixedUpdate()
{
    Vector3 direction = new Vector3(transform.position - lastPosition);
    Ray ray = new Ray(lastPosition, direction);
    RaycastHit hit;
    if (Physics.Raycast(ray, hit, direction.magnitude))
    {
        // Do something if hit
    }

    this.lastPosition = transform.position;
}

Answer 5

• Edit ---> Project Settings ---> Time ... decrease "Fixed Timestep" value .. This will solve the problem but it can affect performance negatively.

• Another solution is could be calculate the coordinates (for example, you have a ball and wall. Ball will hit to wall. So calculate coordinates of wall and set hitting process according these cordinates )

Answer 6

So I haven't been able to get the Mesh Colliders to work. I created a composite collider using simple box colliders and it worked exactly as expected.

Other tests with simple Mesh Colliders have come out the same.

It looks like the best answer is to build a composite collider out of simple box/sphere colliders.

For my specific case I wrote a Wizard that creates a Pipe shaped compound collider.

@script AddComponentMenu("Colliders/Pipe Collider");
class WizardCreatePipeCollider extends ScriptableWizard
{
    public var outterRadius : float = 200;
    public var innerRadius : float = 190;
    public var sections : int = 12;
    public var height : float = 20;

    @MenuItem("GameObject/Colliders/Create Pipe Collider")
    static function CreateWizard()
    {
        ScriptableWizard.DisplayWizard.<WizardCreatePipeCollider>("Create Pipe Collider");
    }

    public function OnWizardUpdate() {
        helpString = "Creates a Pipe Collider";
    }

    public function OnWizardCreate() {
        var theta : float = 360f / sections;
        var width : float = outterRadius - innerRadius;

        var sectionLength : float = 2 * outterRadius * Mathf.Sin((theta / 2) * Mathf.Deg2Rad);

        var container : GameObject = new GameObject("Pipe Collider");
        var section : GameObject;
        var sectionCollider : GameObject;
        var boxCollider : BoxCollider;

        for(var i = 0; i < sections; i++)
        {
            section = new GameObject("Section " + (i + 1));

            sectionCollider = new GameObject("SectionCollider " + (i + 1));
            section.transform.parent = container.transform;
            sectionCollider.transform.parent = section.transform;

            section.transform.localPosition = Vector3.zero;
            section.transform.localRotation.eulerAngles.y = i * theta;

            boxCollider = sectionCollider.AddComponent.<BoxCollider>();
            boxCollider.center = Vector3.zero;
            boxCollider.size = new Vector3(width, height, sectionLength);

            sectionCollider.transform.localPosition = new Vector3(innerRadius + (width / 2), 0, 0);
        }
    }
}