From e76efda4367c117cc302b20ecb1bb88740d1ca2a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Wed, 19 May 2021 22:57:45 +0300
Subject: [PATCH] fix example inflection-1

---
 tests.sql |  3 +--
 wm.sql    | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/tests.sql b/tests.sql
index f8d3931..630fcf1 100644
--- a/tests.sql
+++ b/tests.sql
@@ -16,7 +16,7 @@ create table figures (name text, way geometry);
 insert into figures (name, way) values ('fig3',ST_GeomFromText('LINESTRING(0 0,12 0,13 4,20 2,20 0,32 0,33 10,38 16,43 15,44 10,44 0,60 0)'));
 insert into figures (name, way) values ('fig3-1',ST_GeomFromText('LINESTRING(0 0,12 0,13 4,20 2,20 0,32 0,33 10,38 16,43 15,44 10,44 0)'));
 insert into figures (name, way) values ('fig5',ST_GeomFromText('LINESTRING(0 39,19 52,27 77,26 104,41 115,49 115,65 103,65 75,53 45,63 15,91 0,91 0)'));
-insert into figures (name, way) values ('inflection-1',ST_GeomFromText('LINESTRING(129 45,131 56,130 82,128 99,147 104,149 89,147 68,141 52)'));
+insert into figures (name, way) values ('inflection-1',ST_GeomFromText('LINESTRING(100 14,114 20,133 20,145 15,145 0,136 5,123 7,114 7,111 2)'));
 
 drop table if exists bends;
 create table bends (way geometry);
@@ -35,7 +35,6 @@ begin
   perform assert_equals('LINESTRING(20 2,20 0,32 0,33 10)', st_astext(bends[3]));
   perform assert_equals('LINESTRING(32 0,33 10,38 16,43 15,44 10,44 0)', st_astext(bends[4]));
 
-
   perform assert_equals(4, array_length(detect_bends((select way from figures where name='fig3-1')), 1));
 
   select detect_bends((select way from figures where name='fig5')) into bends;
diff --git a/wm.sql b/wm.sql
index 89e93ac..aa10e0c 100644
--- a/wm.sql
+++ b/wm.sql
@@ -99,18 +99,21 @@ begin
     -- Then edges (A,B) and (E,F) are shared with the neighboring bends.
     --
     --
-    -- Assume this curve:
+    -- Assume this curve (figure `inflection-1`):
     --
     --        A______B
-    --     ---'      `---.___. E
-    --               C   D   |
-    --     _I                |
-    --      '---.________    |
-    --          H       G'---+ F
+    --     ---'      `-------. C
+    --                       |
+    --        G___ F         |
+    --        /   `-----.____+ D
+    --                  E
     --
     -- After processing the curve following the definition of a bend, the bend
-    -- [A-G] would be detected. Assuming inflection point G and H are "small",
-    -- the bend would be extended by two edges to [A,I].
+    -- [A-E] would be detected. Assuming inflection point E and F are "small",
+    -- the bend needs to be extended by two edges to [A,G].
+    --
+    -- Assuming the direction in this example is clock-wise, the first set of
+    -- `p` variables will be: p1=C, p2=B, p3=A.
     for p in (select geom from st_dumppoints(prev_bend) order by path[1] desc) loop
       p3 = p2;
       p2 = p1;