From cea1c6eb2950dd04e54da790b68c1da99d43cd3f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= Date: Wed, 19 May 2021 22:57:45 +0300 Subject: [PATCH] documentation --- wm.sql | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/wm.sql b/wm.sql index c652db8..a3e773d 100644 --- a/wm.sql +++ b/wm.sql @@ -16,6 +16,23 @@ declare begin pi = radians(180); + -- the last vertex is iterated over twice, because the algorithm uses 3 vertices + -- to calculate the angle between them. + -- + -- Given 3 vertices p1, p2, p3: + -- + -- p1___ ... + -- / + -- ..._____/ + -- p3 p2 + -- + -- This loop will use p1 as the head vertex, p2 will be the measured angle, + -- and p3 will be trailing. The line that will be added to the bend will + -- always be [p3,p2]. + -- So once the p1 becomes the last vertex, the loop terminates, and the + -- [p2,p1] line will not have a chance to be added. So the loop adds the last + -- vertex twice, so it has a chance to become p2, and be added to the bend. + -- for p in ( (select (dp).geom from st_dumppoints(line) as dp order by (dp).path[1] asc) union all