koobas.hobune.stream
rigidBody.MovePosition() skips collisions
Hi all.
I have following situation (iOS and android oriented game): object with attached rigidboby, when object is pressed, it moves with the finger on Update().
Update() { ... if (isDragging) mainRigidbody.movePosition(pos); ... }
Than I have another object I need to collide with, but during fast movement of object 1 collision (I use onTrigger function) is not called.
Can anybody advice me how to fix that situation?
Here was my solution to this problem.
Cast a ray from your current position to the desired movePosition. Check if we hit a collider. If so move to the hit location, if not then move as usual.
Vector3 direction = new Vector3(desiredPosition - currentPosition);
Ray ray = new Ray(currentPosition, direction);
RaycastHit hit;
if (!Physics.Raycast(ray,out hit,direction.magnitude))
rigidbody.MovePosition(desiredPosition);
else
rigidbody.MovePosition(hit.point);
There is no solution in the sense that there will always be the chance of an extremely fast object literally missing the collider wall altogether. The only way to stop this would be to have a restriction on the maximal speed, or have an infinitely-wide collider.
But, maybe this will help:
(1) make sure you test for collisions in FixedUpdate(), not Update(), so that the checks occur at exact regular intervals, without the risk of framerate reduction when the CPU is working extra hard (e.g. when scrolling fast!).
(2) to address the collision-miss, that still could occur with if you follow (1), make sure you
(2.1) have a wide-enough collider. You could even program the game so that the collider scales-out when an object is moving very fast. A thin collider has a higher risk of never being touched during the FixedUpdate calls.
(2.2) Failing that, you could record a boolean for the object saying "isLeftOfWall", which switches to true after the object goes through the wall, even if no collision is detected. This can be implemented by checking the coordinates of the wall with the current transform.position to see if your object is left or right of the wall. (Obviously you can do this trick for any axis, not just left/right). Then you just call the collision function (or another function that does the same stuff) as if there was a collision detected.
I would recommend using (2.1). There is no reason why your wall couldn't have a HUGE collider, or two trigger colliders on the left and right side of it, that just reports whether the object is inside it or not.
Here was my solution...
Cast a ray from the current position to the desired move to position. If the ray hits any obstacles handle accordingly, either pass through or move to the hit point.
This seems to be a solution. No matter how fast my object moves it will never pass through another collider.
Thank you for your response!
Ahh yes, I've seen that solution too. Personally, I'm still trying to make sense of Raycast and none of the beginner/intermediate tutorials explain it in a straightforward way, so I tend to just avoid them for now! But I suspect your way is better than $$anonymous$$e.
Maybe you can try to put rigidBody.MovePosition() in FixedUpdate(). In this way the changing in position is synchronized with the physic, namely with collisions
Apparently rigidbody's "continus" mode helps, (I'm trying to figure it out), but if not, raycast works always.
