generate_polygon_rad.fnc

create or replace function generate_polygon_rad(
  p_min_radius    in number,
  p_variance_pct  in number,
  p_lon           in number default 0,
  p_lat           in number default 0)
  return sdo_geometry
is
  c_upper_limit constant number := p_min_radius + p_min_radius*(p_variance_pct/100);
  v_cur_radian number := 0;
  v_x number;
  v_y number;
  
  /* array of point used to construct the polygon */
  v_ordinate_array_points sdo_ordinate_array := sdo_ordinate_array();
begin
  /*
     Each itteration will add a point at a random distance from the center point
     on the current radian.
     asin(1)*4 = 2pi
  */
  while v_cur_radian < asin(1)*4 loop
    select t.x, t.y
      into v_x, v_y
      from table(sdo_util.getvertices(
                     sdo_util.point_at_bearing(
                         sdo_geometry(2001,
                                      4326,
                                      sdo_point_type(p_lon, p_lat, null), null, null),
  /*
     Since sdo_util.getvertices increments radian in a clockwise direction
       and a valid polygon must be defined in a counter-clockwise direction
       we'll change our v_cur_radian to a negative value.
  */
                         v_cur_radian * -1,
                         round(dbms_random.value(p_min_radius,c_upper_limit))
                     )
                 )
                ) t;

    /* add x and y value of new point */
    v_ordinate_array_points.extend(2);
    v_ordinate_array_points(v_ordinate_array_points.count-1) := v_x;
    v_ordinate_array_points(v_ordinate_array_points.count) := v_y;

    /* increment the current radian by .1 to .5 radians */
    v_cur_radian := v_cur_radian + round(dbms_random.value(.1,.5),2);
  
  end loop;

  /* add x and y value of first point as the last point of the polygon to close it */
  v_ordinate_array_points.extend(2);
  v_ordinate_array_points(v_ordinate_array_points.count-1) := v_ordinate_array_points(1);
  v_ordinate_array_points(v_ordinate_array_points.count) := v_ordinate_array_points(2);

  return sdo_geometry(2003,  -- two-dimensional polygon
                      4326,
                      null,
                      sdo_elem_info_array(1,1003,1), -- simple polygon
                      v_ordinate_array_points
                     );
end;