Move rigidbody to a specific position?

Archived Forums Questions & Answers
1

For now I am using:

    Vector3 targetPos = new Vector3(43.4,2,2);
    void Update(){
    transform.position = Vector3.Lerp(transform.position,targetPos,(Time.deltaTime*3)/Vector3.Distance(targetPos,transform.position);
    }

This works nicely , but i need rigidbody with correct velocity and all simulations.

I don’t need rigidbody.MovePosition or rigidbody.position because that works but that doesn’t change velocity.

I need something that will return velocity.

Please provide a fuller description. Your object is at point A. You want to move it to point B over what length of time: single frame? Some specified amount of time? Note if the movement is very large, moving something in a single frame with realistic physics may result in a huge increase in velocity. Or perhaps your object is standing still and when you move it you what the some specified velocity to match the direction of movement? Or perhaps you want to continue the current velocity but in the direction specified by the move?

 –

I want to move it until it reaches the destination with a speed of 2unit/s I think i should do someting like lerp rigidbody.velocity but I don't know how to calculate the velocity so it matches the direction of the point B

 –

2 Answers

2
3

To calculate a directional Vector :

var dir : Vector3 = target.position - transform.position;

to give this vector a magnitude in relation to speed, normalize it then multiply the result by the speed :

var dir : Vector3 = (target.position - transform.position).normalized * speed;

finally, simply apply the vector to the velocity variable of the rigidbody component :

rigidbody.velocity = dir;

Rigidbody :

Vector information :

To see if the rigidbody has reached the target, you could look into how waypoints are used and implemented. But here’s a quick and dirty way to check if a waypoint has been reached :

#pragma strict

var target : Transform;
var speed : float = 2.0;

private var desiredVelocity : Vector3;
private var lastSqrMag : float;

function Start() 
{
	// calculate directional vector to target
	var directionalVector : Vector3 = (target.position - transform.position).normalized * speed;
	
	// reset lastSqrMag
	lastSqrMag = Mathf.Infinity;
	
	// apply to rigidbody velocity
	desiredVelocity = directionalVector;
}

function Update() 
{
	// check the current sqare magnitude
	var sqrMag : float = (target.position - transform.position).sqrMagnitude;
	
	// check this against the lastSqrMag
	// if this is greater than the last,
	// rigidbody has reached target and is now moving past it
	if ( sqrMag > lastSqrMag )
	{
		// rigidbody has reached target and is now moving past it
		// stop the rigidbody by setting the velocity to zero
		desiredVelocity = Vector3.zero;
	} 
	
	// make sure you update the lastSqrMag
	lastSqrMag = sqrMag;
}

function FixedUpdate() 
{
	rigidbody.velocity = desiredVelocity;
}

Thanks. What if i want to rotate the character to look at the target? Transform.LookAt works , but as i said i need velocities. How can I use something like rigidbody.angularVelocity?

 –

Can I contact you? We might help eachother. I am working on some maths for interpolation/extrapolation on photon. I've got RTS camera and i click where I want the character to go. Anyway I am thinking about ditching rigidbodies and using Navigation on my character. BTW marked as accepted. Even though I solved it using something even easier (rigidbody.velocity = transform.forward)

 –

You can send personal messages from the forum, click on your name where it says Welcome, [username]. After hearing what you are working on, I think I'm out of my depth here!

 –
2

Assuming you are using a rigidbody, and assuming there are no other forces (like gravity) impacting the rigidbody, you can do something like:

rigidbody.velocity = (targetPos - transform.position).normalized * speed;

Note this is done once, not in every frame. And it will not stop at your targetPos unless you write code to make it stop. ‘speed’ is a variable you define, will be in units per second, and for your question would be 2.0.