[SOLVED]: bullet passing through object in specific condition

Questions & Answers
1

Hi there,

I have first person shooting game where the camera is fixed. The player shoots at moving shapes.
-I have a cube that has a rigidbody and a bunch of child colliders that break it up into zones.
-I also have invisible walls that prevent the shapes from moving off camera or too close to the camera (and therefore the bullet must always pass through one or more invisible walls to get to a shape). The invisible walls are box colliders.
-When the bullet is fired, I use IgnoreCollision on all the invisible walls with the bullet.
-The bullet has a rigidbody with continuous dynamic collision detection and a sphere collider
-The cube has discrete collision detection (rigidbody/collider setup mentioned above)

This works fine when the shape is near the center of the screen or has distance from the invisible walls. However if the shape is very close to an invisible wall and very close to the edge of the screen (sharp angle from projectile), the bullet will pass through the shape and hit the wall behind it. I have attached to both of them this “DontGoThroughThings.js” script that creates raycasts every frame to ensure that it will not pass through things:

   // http://www.unifycommunity.com/wiki/index.php?title=DontGoThroughThings

#pragma strict 

var layerMask : LayerMask; //make sure we aren't in this layer 
var skinWidth : float = 0.1; //probably doesn't need to be changed 
private var minimumExtent : float; 
private var partialExtent : float; 
private var sqrMinimumExtent : float; 
private var previousPosition : Vector3; 
private var myRigidbody : Rigidbody; 
//initialize values 
function Awake() { 
	if (name.Contains("zone")) {
		myRigidbody = transform.parent.rigidbody;
	}
	else {
   		myRigidbody = rigidbody; 
	}
   previousPosition = myRigidbody.position; 
   minimumExtent = Mathf.Min(Mathf.Min(collider.bounds.extents.x, collider.bounds.extents.y), collider.bounds.extents.z); 
   partialExtent = minimumExtent*(1.0 - skinWidth); 
   sqrMinimumExtent = minimumExtent*minimumExtent; 
} 

function FixedUpdate() { 
   //have we moved more than our minimum extent? 
   var movementThisStep : Vector3 = myRigidbody.position - previousPosition; 
   var movementSqrMagnitude : float = movementThisStep.sqrMagnitude;
   if (movementSqrMagnitude > sqrMinimumExtent) { 
      var movementMagnitude : float = Mathf.Sqrt(movementSqrMagnitude);
      var hitInfo : RaycastHit; 
      //check for obstructions we might have missed 
      if (Physics.Raycast(previousPosition, movementThisStep, hitInfo, movementMagnitude, layerMask.value)) {
      if (hitInfo.transform.gameObject.tag!="InvisWall") {
         myRigidbody.position = hitInfo.point - (movementThisStep/movementMagnitude)*partialExtent; 
      }
      }
   } 
   previousPosition = myRigidbody.position; 
}

Does anyone have any insight into why this might happen?

Thanks,
Candace

EDIT

Solution: Removed invisible walls and changed shapes to follow a waypoint system for movement.

2

Well, if you want to, a easier way to solve this would be to make the gun fire Raycasts instead of actual bullets. Then you just make the invisible walls a different layer that is not affected by these raycasts, but the targets still are. Also, for what reason do you have the invisible walls for? Would it be easier just making a Waypoint system that the targets follow? But back to your original question. It might pass through because the bullets are moving to fast, or your frame rate is to low or a combination. I’ve had problems like this on very slow computers. There could be other reasons such as you are using trigger colliders (I doubt that though) instead of actual colliders.

3

Just off the top of my head, but:

  1. Set bullet as a trigger by default
  2. Fire bullet from behind wall, so it must travel all the way through it.
  3. Set up OnTriggerExit() on the walls that turns bullet trigger off, which should re-enable physics detection(and thus destroy the bullet if it hits the back invisible wall)