Data commit

Task/Fractal-tree/PL-pgSQL/fractal-tree-1.sql

@@ -0,0 +1,43 @@
+drop table if exists my_temp_tree_table;
+
+do $$
+declare
+  _length numeric := 1;
+  -- a little random
+  _random_length_reduction_max numeric := 0.6;
+  _fork_angle numeric := pi()/12;
+  -- a little random
+  _random_angle numeric := pi()/12;
+  _depth numeric := 9 ;
+
+begin
+    create temporary table my_temp_tree_table as
+        WITH RECURSIVE branch(azimuth, x1, y1, x2, y2, len, n) AS (
+            VALUES (pi()/2, 0.0, 0.0, 0.0, _length, _length, _depth)
+          UNION all
+            select azimuth+a,
+                x2, y2,
+                round((x2+cos(azimuth+a)*len)::numeric, 2), round((y2+sin(azimuth+a)*len)::numeric, 2),
+                (len*(_random_length_reduction_max+(random()*(1-_random_length_reduction_max))))::numeric,
+                n-1
+            FROM branch
+            cross join (
+                select ((-_fork_angle)+(_random_angle)*(random()-0.5)) a
+                union
+                select ((_fork_angle)+(_random_angle)*(random()-0.5)) a2
+            ) a
+            WHERE n > 0
+        )
+        select x1, y1, x2, y2, 'LINESTRING('||x1||' '||y1||','||x2||' '||y2||')' as wkt from branch
+        ;
+end $$
+;
+
+-- coordinates and WKT
+select * from my_temp_tree_table;
+
+-- binary version (postgis) of each branch
+select ST_GeomFromEWKT('SRID=4326;'||wkt) geom from my_temp_tree_table;
+
+-- a unique geometry
+select st_union(ST_GeomFromEWKT('SRID=4326;'||wkt)) geom from my_temp_tree_table;

Task/Fractal-tree/PL-pgSQL/fractal-tree-2.sql

@@ -0,0 +1,14 @@
+WITH RECURSIVE noeuds(azimuth, x0, y0, x, y, len, n) AS (
+    VALUES (pi()/2, 0::real, 0::real, 0::real, 10::real, 10::real, 9::int)
+  UNION all
+    select azimuth+a, x, y, (x+cos(azimuth+a)*len)::real, (y+sin(azimuth+a)*len)::real, (len/2)::real, n-1
+    FROM noeuds
+    cross join (select (-pi()/7)::real a union select (pi()/7)::real a2) a
+    WHERE n > 0
+)
+, branche as (
+    select '('||x0||' '||y0||','||x||' '||y||')' b
+    from noeuds
+)
+select ST_GeomFromEWKT('SRID=4326;MULTILINESTRING('||string_agg(b, ',')||')') tree
+from branche