constructor(lon, lat, r) {

    this.lon = lon;

    this.lat = lat;

    this.pos = this.lonlat2pos(lon, lat);

    this.r = r;

  }

​

  lonlat2pos(lon, lat) {

    return (new createVector(width / (2 * PI) * (PI + this.lon), height / (PI) * (this.lat)))

  }

​

  update() {

    this.pos = this.lonlat2pos(this.lon, this.lat);

  }

​

  show(mode) {

    if (mode == 1) {

      const dtheta = 0.01;

      stroke(255);

      strokeWeight(2);

      for (let theta = 0; theta <= 2 * PI; theta += dtheta) {

        for (let xi = -1; xi <= 1; xi++) {

          for (let yi = 0; yi <= 0; yi++) {

            line(this.pos.x + this.r * cos(theta) + xi * width,

              this.pos.y + this.r * sin(theta) + yi * height,

              this.pos.x + this.r * cos(theta - dtheta) + xi * width,

              this.pos.y + this.r * sin(theta - dtheta) + yi * height);

          }

        }

      }

    }

  }

​

  move(dlon, dlat) {

    this.lon = (this.lon + dlon + 2 * PI) % (2 * PI);

    if (this.lat + dlat > PI) {

      this.lat = 2 * PI - dlat - this.lat;

      this.lon = (PI+this.lon)%(2*PI);

    } else if (this.lat + dlat < 0) {

      this.lat = - this.lat - dlat;

      this.lon = (PI+this.lon)%(2*PI);

    } else {

      this.lat = this.lat + dlat;

    }

  }

}