unity3d - 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 wall.

I am using a Box Collider on the player, and a Mesh Collider for the level's wall. I am having issues with both a Player Character (a space ship) that the movement is controlled by the player. And with projectiles, which are fire and forget moving at a constant speed.

This is my movement code for my player. It is being run in the FixedUpdate() function.

//Movement
    haxis = Input.GetAxis("Horizontal") * speed;
    vaxis = Input.GetAxis("Vertical") * speed;

    moveVector.x = haxis;
    moveVector.z = vaxis;

    if(moveVector.magnitude > 1)
    {
        moveVector.Normalize();
    }

    rigidbody.MovePosition(transform.position + moveVector * speed);

With the bullets, they are given a velocity and the engine calculates their moviements. They are using Box Collider and it is set as a Trigger so they don't have physics. But I use OnTriggerEnter to destroy them.

//Projectiles without physics collisiions
function OnTriggerEnter (other : Collider) {
    Destroy(gameObject);
}

Some, but not all of the bullets will be destroyed when hitting the mesh collider wall. The player will sometimes hit it and stop, but can usually push through it. How can I make the collisions with the mesh collider work every time?

Answer 1

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;
}