Keeping Rigidbody Within Distance From Point

Unity Engine
1

I’m trying to keep a rigidbody from moving beyond a certain distance from a point. I’ve tried using joints, but the don’t allow the rigidbody to move freely within the radius- they snap back to their initial position.

Does anyone have any ideas?

2

You might be able to do something with this:

So you calculate the vector from the point to the rigidbody and then you limit the maximum magnitude/length/distance that is allowed between the point and rigidbody :slight_smile: And you just do that in Update() or maybe in FixedUpdate(). I don’t know if this will work well with a rigidbody with physics applied to it though…

3

I think a configurable joint with Linear Limit set to your radius would do what you want.

4

Hmmm. That might work, but you still have to deal with physics…

Tried that. Problem is the radius is from the initial position of the attached object, not the point I want the system to be limited to.

5

Have you set the Connected Anchor to be the point you want to circle?

6

(Sorry for late response)

Yes. It works if I create the joint in the editor, but if I do it via script, it doesn’t constrain the object. Code:

					//Stick Tether
					tetherTransform.position = hit.point;			
					tetherIsExtending = false;
					tetherIsMoving = false;	
					
					tetherTransform.rigidbody.mass = 800;
					
					myJoint	= tetherTransform.gameObject.AddComponent(ConfigurableJoint);
					myJoint.anchor = Vector3(0,0,0);
					myJoint.axis = Vector3(0,0,0);
					
					myJoint.linearLimit.limit = maxTetherRange/2;
					myJoint.linearLimit.spring = 0;
					
					myJoint.xMotion = ConfigurableJointMotion.Limited; 
					myJoint.yMotion = ConfigurableJointMotion.Limited; 
					myJoint.zMotion = ConfigurableJointMotion.Limited; 
					
                                        //These were the editor defaults, but they default to zero if the joint is created via script
					myJoint.xDrive.maximumForce = 3.402823e+38;
					myJoint.yDrive.maximumForce = 3.402823e+38;
					myJoint.zDrive.maximumForce = 3.402823e+38;
					
					tetherJoint = hit.transform.gameObject.AddComponent(FixedJoint);
										
					tetherJoint.connectedBody = tetherTransform.rigidbody;
					myJoint.connectedBody = myRigidbody;