How can I create objects that are placed along the circumference of a circle,and then expand and contract the circle

Questions & Answers
1

I’m just starting to learn unity2d and I’m trying to create rotating obstacles that expand and contract.The obstacles are supposed to be in the pattern of a circle,which needs to keep rotating.
I first created multiple objects and then added the following code to each,with each object having a different angle.
Here is the code I’ve got for rotation and the expansion.But there is something wrong with it that makes the looping go wrong.

	void Update()
	{
		if (radius < 1) {
			angle += speed * Time.deltaTime;     
			radius += speed * Time.deltaTime; 
		} 
		if (radius > 5) {
			angle -= speed * Time.deltaTime;     
			radius -= speed * Time.deltaTime; 
		} 


		x = Mathf.Cos (angle) * radius;
		y = Mathf.Sin (angle) * radius;
		transform.position = new Vector3 (x,y, -5);
		
			

	}
3

You probably want to use different speed values when computing your angle, and radius changes.

I’m not sure what the if(radius<0) is supposed to detect- don’t you always want to have a (radius >0)? If this is to check the minimal size of the circle, I don’t see where you check for the maximum size of the circle radius?

May I suggest, that instead of if-statements, you use another SIN function to add/subtract a cycling amount from your radius.

e.g.

 angle += speed * Time.deltaTime;
 float sin_value = Mantf.Sin(radius_speed * Time.time);
 float current_radius = base_radius + (radius_flux_size * sin_value);
 float x = Mathf.Cos (angle) * current_radius ;
 float y = Mantf.Sin(angle);  * current_radius ;
 transform.position = new Vector3 (x,y, -5);
2

public float angleOffset = 0;

float rotateSpeed = 5f;
float maxRadius = 0.5f;
float minRadius = 0.25f;
float oscillateSpeed = 0.1f;

float radius = 0.5f;
float angle;
float t = 0;

void FixedUpdate () 
{
    t += oscillateSpeed;
    var v = Mathf.Sin(t); //gives you a value between -1 and 1
    v = (v + 1) / 2; //v is now between 0 and 1
    v = minRadius + v * (maxRadius - minRadius); //
    radius = v;
    print(v);
    

    angle += rotateSpeed;
    var rotation = Quaternion.AngleAxis(angle + angleOffset, Vector3.forward);
    transform.position = rotation * (Vector3.right * radius);
}