commit c0d9a3de7fc4f7be97819f67d38366c44f478358 (tree)
parent 4a32d2f7ded04b326d59713845a47b2aa10115db
Author: Motiejus Jakštys <motiejus@uber.com>
Date: Thu, 15 Apr 2021 16:55:47 +0300
move section of self_crossing to a separate function
Diffstat:
| M | IV/wm.sql | | | 65 | +++++++++++++++++++++++++++++++++++++++-------------------------- |
1 file changed, 39 insertions(+), 26 deletions(-)
diff --git a/IV/wm.sql b/IV/wm.sql
@@ -209,6 +209,34 @@ begin
end
$$ language plpgsql;
+drop function if exists if_selfcross;
+create function if_selfcross(
+ bendi geometry,
+ bendj geometry
+) returns geometry as $$
+declare
+ a geometry;
+ b geometry;
+ partitions geometry;
+begin
+ a = st_pointn(bendi, 1);
+ b = st_pointn(bendi, -1);
+ partitions = st_split(bendj, st_makeline(a, b));
+
+ if st_numgeometries(partitions) = 1 then
+ return null;
+ end if;
+
+ if st_numgeometries(partitions) = 2 and
+ (st_contains(bendj, a) or st_contains(bendj, b)) then
+ return null;
+ end if;
+
+ return partitions;
+end
+$$ language plpgsql;
+
+
-- self_crossing eliminates self-crossing from the bends, following the
-- article's section "Self-line Crossing When Cutting a Bend".
drop function if exists self_crossing;
@@ -220,7 +248,6 @@ declare
pi constant real default radians(180);
i int4;
j int4;
- prev_length int4;
a geometry;
b geometry;
multi geometry;
@@ -234,25 +261,18 @@ begin
-- self-crossing. now try to find another bend in this line that
-- crosses an imaginary line of end-vertices
+ -- To understand the block below, I suggest you take a pencil and paper,
+ -- draw a self-crossing bend (fig6 from the article works well), and
+ -- figure out what happens here, by hand. I know it's hard to follow.
+ -- Apologies.
+
-- go through each bend in the given line, and see if has a potential to
-- cross bends[i].
for j in 1..i-1 loop
- a = st_pointn(bends[i], 1);
- b = st_pointn(bends[i], -1);
- multi = st_split(bends[j], st_makeline(a, b));
- continue when st_numgeometries(multi) = 1;
- continue when st_numgeometries(multi) = 2 and
- (st_contains(bends[j], a) or st_contains(bends[j], b));
-
- -- vertices, segments and stars are aligned, we are changing the bend
+ select if_selfcross(bends[i], bends[j]) into multi;
+ continue when multi is null;
mutated = true;
- -- To understand the block below, I suggest you take a pencil and paper,
- -- draw a self-crossing bend (fig6 from the article works well), and
- -- figure out what happens here, by hand. I know it's hard to follow.
- -- Apologies.
- prev_length = array_length(bends, 1);
-
-- remove first vertex of the following bend, because the last
-- segment is always duplicated with the i'th bend.
bends[i+1] = st_removepoint(bends[i+1], 0);
@@ -262,26 +282,19 @@ begin
st_npoints(bends[j])-1,
st_pointn(bends[i], st_npoints(bends[i]))
);
- bends = bends[1:j] || bends[i+1:prev_length];
+ bends = bends[1:j] || bends[i+1:];
exit;
end loop;
for j in reverse array_length(bends, 1)..i+1 loop
- a = st_pointn(bends[i], 1);
- b = st_pointn(bends[i], -1);
- multi = st_split(bends[j], st_makeline(a, b));
- continue when st_numgeometries(multi) = 1;
- continue when st_numgeometries(multi) = 2 and
- (st_contains(bends[j], a) or st_contains(bends[j], b));
-
- -- vertices, segments and stars are aligned, we are changing the bend
+ select if_selfcross(bends[i], bends[j]) into multi;
+ continue when multi is null;
mutated = true;
-- To understand the block below, I suggest you take a pencil and paper,
-- draw a self-crossing bend (fig6 from the article works well), and
-- figure out what happens here, by hand. I know it's hard to follow.
-- Apologies.
- prev_length = array_length(bends, 1);
-- remove last vertex of the previous bend, because the last
-- segment is duplicated with the i'th bend.
bends[i-1] = st_removepoint(bends[i-1], st_npoints(bends[i-1])-1);
@@ -290,7 +303,7 @@ begin
st_pointn(bends[i], 1),
st_removepoint(st_geometryn(multi, st_numgeometries(multi)), 0)
);
- bends = bends[1:i] || bends[j+1:prev_length];
+ bends = bends[1:i] || bends[j+1:];
exit;
end loop;
end loop;
