Moving smoothly around the bounds of a circle

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This is the image of what I'm trying to achieve, in a 3D space. I want the object to follow my finger within the green zone, but stay on the edge of the green zone if I move my finger outside of it. I have achieved this with the code below, but when moving my finger around the red zone a lot of jitters and clipping occurs as the object keeps snapping back within it's bounds. My main camera is attached to the moving object so it's important that I eliminate the jitters. How can I smooth this out?

 public class Player : MonoBehaviour
 {
     public Camera movementCam;
     readonly float radius = 0.45f;
     readonly float speed = 3f;
     Ray firstTouchPos;
     Vector2 playerPos;
 
     void Update()
     {
         if (Input.GetMouseButtonDown(0)) {
             firstTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
             playerPos = transform.position;
         }
 
         if (Input.GetMouseButton(0)) {
             Ray currentTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
             Vector2 direction = currentTouchPos.origin - firstTouchPos.origin;
             float distance = Vector3.Distance(transform.position, Vector3.zero);
             transform.position = distance >= radius ? (Vector3)(direction.normalized * radius) : (Vector3)(playerPos + direction * speed);
         }
     }
 }

Answer 1

You can achieve this by using Lerp or Slerp. See example below

 public Camera movementCam;
      readonly float radius = 0.45f;
      readonly float speed = 3f;
      Ray firstTouchPos;
      Vector2 playerPos;
  
      void Update()
      {
          if (Input.GetMouseButtonDown(0)) {
              firstTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
              playerPos = transform.position;
          }
  
          if (Input.GetMouseButton(0)) {
              Ray currentTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
              Vector2 direction = currentTouchPos.origin - firstTouchPos.origin;
              float distance = Vector3.Distance(transform.position, Vector3.zero);
              var targetPosition = distance >= radius ? (Vector3)(direction.normalized * radius) : (Vector3)(playerPos + direction * speed);
              transform.position = Vector3.Lerp (transform.position, targetPosition, 1f); 
          }
      }

However, I would recommend you put the slerp function outside of the MouseButtonDown. That way you can add a smoother following/delay

 readonly float radius = 0.45f;
      readonly float speed = 3f;
      Ray firstTouchPos;
      Vector2 playerPos;
      Vector3 targetPosition;
      float followDelay = 2f;
      void Update()
      {
          if (Input.GetMouseButtonDown(0)) {
              firstTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
              playerPos = transform.position;
          }
  
          if (Input.GetMouseButton(0)) {
              Ray currentTouchPos = movementCam.ScreenPointToRay(Input.mousePosition);
              Vector2 direction = currentTouchPos.origin - firstTouchPos.origin;
              float distance = Vector3.Distance(transform.position, Vector3.zero);
              targetPosition = distance >= radius ? (Vector3)(direction.normalized * radius) : (Vector3)(playerPos + direction * speed);
             
          }
          
           transform.position = Vector3.Lerp (transform.position, targetPosition, followDelay); 
      }

Moving smoothly around the bounds of a circle

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