Changes between Version 11 and Version 12 of UsersWikiplpgsqlfunctions

Timestamp:

09/09/09 21:32:39 (15 years ago)

Author:

bcrosby

Comment:

--

UsersWikiplpgsqlfunctions

@@ -5 +5 @@
 ==  This is an area to put utility functions or wrappers around PostGIS ==
 
- * '''Generate an arc given two points on the arc and the centre point'''
+ * '''Generate an arc given two points on the arc, the centre point and direction'''
 
 {{{
 #!sql
- CREATE OR REPLACE FUNCTION st_createarc(startpoint geometry, endpoint geometry, arcenter geometry)
+ CREATE OR REPLACE FUNCTION st_createarc(startpoint geometry, endpoint geometry, arcenter geometry,direction text)
   RETURNS geometry AS
   $$
@@ -15 +15 @@
     pointonarc geometry;
     thearc text;
+    thedirection float;
   BEGIN
-        pointonarc := ST_Translate( ST_Rotate( ST_Translate( startpoint, -1*ST_X(arcenter), -1*ST_Y(arcenter)), pi()/5), ST_X(arcenter), ST_Y(arcenter));
-    thearc := 'CIRCULARSTRING('||ST_X(startpoint)||' '||ST_Y(startpoint)||','||ST_X(pointonarc)||' '||ST_Y(pointonarc)||','||ST_X(endpoint)||' '||ST_Y(endpoint)||')';
+        IF direction = 'cc' THEN thedirection := pi()/5; ELSE thedirection := -1*pi()/5; END IF;
+        pointonarc := ST_Translate( ST_Rotate( ST_Translate( startpoint, -1*ST_X(arcenter), -1*ST_Y(arcenter)), thedirection), ST_X(arcenter), ST_Y(arcenter));
+        thearc := 'CIRCULARSTRING('||ST_X(startpoint)||' '||ST_Y(startpoint)||','||ST_X(pointonarc)||' '||ST_Y(pointonarc)||','||ST_X(endpoint)||' '||ST_Y(endpoint)||')';
         RETURN st_transform(st_curvetoline(st_transform(st_setsrid(thearc,st_srid(arcenter)),utmzone(arcenter))),st_srid(arcenter));
   END;
   $$
   LANGUAGE 'plpgsql' IMMUTABLE;
-  COMMENT ON FUNCTION st_createarc(geometry,geometry,geometry) IS 'Generates an arc based on starting point, ending point and centre of arc. All geometries must be of type POINT and this function returns a linestring of the arc based on the original SRID and 32 points per quarter circle. Requires the utmzone function.'; 
+  COMMENT ON FUNCTION st_createarc(geometry,geometry,geometry,text) IS 'Generates an arc based on starting point, ending point,centre of arc, and direction. All geometries must be of type POINT and direction must be "cc" (counter-clockwise) or "cw" (clockwise).This function returns a linestring of the arc based on the original SRID and 32 points per quarter circle. Requires the utmzone function.'; 
+ 
 }}}