unity

unity

            RaycastHit rcHit = new RaycastHit();

            Ray bottom = new Ray(this.transform.position,Vector3.down);

            if (Physics.Raycast(bottom,out rcHit,20))
            {
                double posy = transform.position.y;
                //with this you rotate object to adjust with terrain
                transform.rotation = Quaternion.Slerp(
                    transform.rotation, 
                    Quaternion.FromToRotation(Vector3.up*Time.deltaTime, rcHit.normal),
                    Time.deltaTime
                );
            }