Extrude 3D polygons in Oracle spatial

Question

Dear Everyone,
I have two data sets of the city footprints imported in the Oracle Spatial already. One is a 2D polygon layer with only x and y, and the other is a 3D polygon layer with z values (the x and y are identical to the first one).
Now I am trying to extrude the 3D polygon to 3D composites based on the z value. I can successfully extrude the 2D polygons with specifying the ground heights (say sdo_ordinate_array(0)) and topheights (say, sdo_ordinate_array(20.0)).
However, how to extrude the 3D polygon taking each vertex's z value as the ground heights to an specified top heights is a problem for me. Since, I am very new to use PL/SQL, besides, I am not sure if it is possible to do this.
Here is the sample data extracted from the sample data:
select sample.geom.sdo_ordinates from sample2d_polygon sample
NUMBER(715202.739577727,733492.909091357,715206.759608945,733492.412077086,715208.666575034,733506.889047512,715204.72752625,733507.364066093,715202.739577727,733492.909091357)
select sample.geom.sdo_ordinates from sample3d_polygon sample
NUMBER(715202.739577727,733492.909091357,12.4890003204346,715206.759608945,733492.412077086,12.4890003204346,715208.666575034,733506.889047512,12.4540004730225,715204.72752625,733507.364066093,12.4320001602173,715202.739577727,733492.909091357,12.4890003204346)
Can anybody help me about this
select sdo_util.extrude(sample.geom, sdo_ordinate_array(), sdo_ordinate_array(20.0), 'true', 0.05) from sample2d_polygon sample, where the first sdo_ordinate_array is the array of corresponding vertex's z value?
Any suggestions is anticipated and highly appreciated.
Sincerely
Jun

Answer 1

Hi Jun,-
I hope the following code solves your problem.
Please also make sure your geometries are valid using sdo_geom.validate_geometry_with_context or
sdo_geom.validate_layer_with_context for 3D geometries.
Please let us know if you have questions.
Best
baris
drop table myGeoms;
drop table extruded_myGeoms;
create table myGeoms(i number, geom sdo_geometry);
insert into myGeoms(i, geom) values(1,
MDSYS.SDO_GEOMETRY(3003, null,null,
MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1),
MDSYS.sdo_ordinate_array(
715202.739577727,733492.909091357,12.4890003204346,
715206.759608945,733492.412077086,12.4890003204346,
715208.666575034,733506.889047512,12.4540004730225,
715204.72752625, 733507.364066093,12.4320001602173,
715202.739577727,733492.909091357,12.4890003204346
insert into myGeoms(i, geom) values(2,
MDSYS.SDO_GEOMETRY(3003, null,null,
MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1),
MDSYS.sdo_ordinate_array(
715202.739577727,733492.909091357,14.4890003204346,
715206.759608945,733492.412077086,14.4890003204346,
715208.666575034,733506.889047512,14.4540004730225,
715204.72752625, 733507.364066093,14.4320001602173,
715202.739577727,733492.909091357,14.4890003204346
insert into myGeoms(i, geom) values(3,
mdsys.sdo_geometry(3003, null, null,
mdsys.sdo_elem_info_array(1,1003,1),
mdsys.sdo_ordinate_array(1,1,10,  0,1,10, 0,0,10, 1,0,10, 1,1,10))
create table extruded_myGeoms(id number, geom sdo_geometry);
-- This program assumes that each geometry in myGeoms table
-- has only 1 ring per polygon ie, 1003 etype element.
set serveroutput on;
declare
type cursor_type is REF CURSOR;
query_crs cursor_type ;
-- For each extruded geometry (result), this array has the ground heights
ords_bottom_z_array sdo_number_array  := null;
-- For each extruded geometry (result), this array has the top heights which is set to 20 for each element.
-- Both arrays must have the same number of elements.
ords_top_z_array sdo_number_array  := null;
ords2d mdsys.sdo_ordinate_array  := null;
result sdo_geometry;
g1 sdo_geometry;
g2d sdo_geometry;
stmt  varchar2(100);
id1 number;
cnt integer;
k integer;
l integer;
the_dim        number;
gtype_2d       number;
begin
stmt := ' select i, geom from myGeoms ';
OPEN query_crs FOR stmt;
LOOP
  BEGIN
   FETCH query_crs into id1, g1;
   EXIT when query_crs%NOTFOUND ;
   ords2d := mdsys.sdo_ordinate_array();
   ords_bottom_z_array := SDO_NUMBER_ARRAY();
   ords_top_z_array := SDO_NUMBER_ARRAY();
   k:=ords_bottom_z_array.count;
   l:=ords2d.count;
   FOR cnt in 1..g1.sdo_ordinates.count LOOP
     if (mod(cnt, 3) = 0) then
       -- Get z values of polygon
       ords_bottom_z_array.extend(1);
       ords_top_z_array.extend(1);
       k:=k+1;
       ords_bottom_z_array(k) := g1.sdo_ordinates(cnt);
       ords_top_z_array(k) := 20.0; -- Constant
     else
       -- To have 2D geometry for input to sdo_util.extrude
       ords2d.extend(1);
       l := l+1;
       ords2d(l) := g1.sdo_ordinates(cnt);
     end if;
   end loop;
   the_dim := floor(g1.sdo_gtype / 1000);
   gtype_2d := (the_dim-1)*1000 + mod(g1.sdo_gtype, 10);
   g2d:= sdo_geometry(gtype_2d, null,  null,
           mdsys.sdo_elem_info_array(1,1003,1),
           ords2d);
   result:= sdo_util.extrude(g2d, ords_bottom_z_array, ords_top_z_array, 'FALSE', 0.05);
   -- insert the extruded geometry (result) into new table
   insert into extruded_myGeoms(id, geom) values(id1, result);
   dbms_output.put_line('id = '||id1);
  END;
END LOOP;
end;
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