How can I get a rigidbody to follow my cursor without penetrating through colliders?

Question

I'm trying to get a rigidbody to follow a target point (controlled by the mouse) that is moving around inside an enclosed mesh collider for my level. If the target point leaves the mesh collider, I need to guarantee that the rigidbody stays inside. I.e. if it can't reach the target point, it calmly presses against the mesh collider until it can.

I tried using rigidbody.MovePosition, but the rigidbody "bleeds through" walls it pushes up against, then starts vibrating violently and finally penetrates right through when the target point moves outside the mesh collider.

I tried implementing my own version of "MovePosition" by calculating the rigidbody's velocity to match the target point's position, but there was near-identical behavior as MovePosition.

Is there some way I haven't thought of to achieve what I'm after? Thanks!

Answer 1

Best Answer

Answer by calbar · Sep 29, 2013 at 07:47 PM

I stuck with adjusting the velocity according to mouse displacement and switched Collision Detection to Continuous, which solved my issues with penetration. A simplified version of my movement code:

rigidbody.velocity = ( ( transform.right * mouseMovement.x ) + ( transform.forward * mouseMovement.y ) ) / Time.deltaTime;

The rigidbodies still have an ugly jitter when they collide with walls, especially in corners. I've smoothed this out by averaging the last couple frames of motion, so while it feels slightly mushy, at least it's smooth and not going through walls.

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tfishell · Oct 18, 2020 at 01:08 AM 0

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I'm not sure if too much time has passed on this question for me to reasonably expect an answer, but can you explain what you meant by "averaging the last couple frames of motion"?

Answer 2

Answer by Nexxiom · Aug 31, 2016 at 07:54 AM

             Collider2D col1,col2;
             col1 = GameObject.Find("objectname").gameObject.GetComponent<Collider2D>();
             col2 = GameObject.Find("objectname").gameObject.GetComponent<Collider2D>();
             Physics2D.IgnoreCollision(col1, col2, true);

This works great! @calbar

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Answer 3

Answer by DanielKhoroshko · Mar 15, 2015 at 11:24 AM

After a few hours of pain I went to this simple code

  Vector3 destintaion; //you fetch it in advance
  float sens = 10; //sensetivity
  
  GetComponent<Rigidbody>().velocity = (destination - transform.position) * sens;

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Answer 4

Answer by robertbu · Sep 24, 2013 at 01:00 AM

How about upping the drag some and then using AddForce() to move the object in the direction of the cursor. I just ran a quick test with a sphere inside four wall with the following code, and it worked fine:

 #pragma strict
 
 function Update () {
     var pos = Input.mousePosition;
     pos.z = -Camera.main.transform.position.z;
     pos = Camera.main.ScreenToWorldPoint(pos);
     var dir = pos - transform.position;
     rigidbody.AddForce(dir * 10);
 }

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calbar · Sep 29, 2013 at 07:29 PM 0

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Thanks for your reply robertbu.

Unfortunately, I've found AddForce to be really unwieldy for getting precise, controllable results. It always ends up with me experimenting with values until it just "looks right", and in some cases this is totally O$$anonymous$$!

But in this case, trying to get my object to follow mouse movements closely resulted in a lot of lagging behind and over-shooting, even when using the VelocityChange force mode for some reason.

It's entirely possible my understanding sucks or I was too impatient to figure out the math, but I opted for adjusting the velocity directly. Feel free to chime in if there's anything I may have missed or misunderstood. :)

How can I get a rigidbody to follow my cursor without penetrating through colliders?

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