Third Person Camera Movement control.

You could use a raycast starting from the camera that tells it when there's a wall nearby.

enter code hereFinally find the solution for avoiding T$$anonymous$$rdperson camera entering the wall or mesh.Use Physics.Raycast to detect the object or wall opposite to T$$anonymous$$rdperson.

 Vector3 orgpos=new Vector3(0.0f,0.0f,0.0f);
     Vector3 objpos = transform.TransformPoint(0, height, -distance);
     
     Transform cameraTransform;
     void Update()
     {
         RaycastHit $$anonymous$$t;
         Vector3 back = transform.TransformDirection (-1 * Vector3.forward); 
     
         if (Physics.Raycast (transform.TransformPoint (orgpos), back, out $$anonymous$$t, distance) && $$anonymous$$t.transform != transform) {
             objpos.x = $$anonymous$$t.point.x;
             objpos.z = $$anonymous$$t.point.z;
             objpos.y = Mathf.Lerp ($$anonymous$$t.point.y, objpos.y, Time.deltaTime);    
         } 
         cameraTransform.position = Vector3.Lerp (cameraTransform.position, objpos, Time.deltaTime);
     }

Add the script to player and assign camera as target.