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wip self-crossing

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Motiejus Jakštys 2021-03-04 14:25:50 +02:00
parent 545aff111f
commit 72f89360f7
1 changed files with 33 additions and 17 deletions
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40
IV/wm.sql
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@ -41,9 +41,8 @@ begin
p3 = p2;
p2 = p1;
p1 = p;
if p3 is null then
continue;
end if;
continue when p3 is null;
cur_sign = sign(pi - st_angle(p1, p2, p2, p3));
if bend is null then
@ -169,10 +168,12 @@ declare
j int4;
pi real;
angle real;
p geometry;
p0 geometry;
p1 geometry;
p2 geometry;
p3 geometry;
s2 real;
s3 real;
bend geometry;
begin
pi = radians(180);
@ -183,28 +184,43 @@ begin
p1 = null;
p2 = null;
p3 = null;
for p in (select geom from st_dumppoints(bends[i]) order by path[1] asc) loop
for p0 in (select geom from st_dumppoints(bends[i]) order by path[1] asc) loop
p3 = p2;
p2 = p1;
p1 = p;
if p3 is null then
continue;
end if;
p1 = p0;
continue when p3 is null;
angle = angle + abs(pi - st_angle(p1, p2, p3));
end loop;
if abs(angle) > pi then
raise notice 'maybe self-crossing bend %: %', st_astext(bends[i]), round(degrees(abs(angle)));
continue when abs(angle) <= pi;
-- sum of inflection angles for this bend is >180, so it may be self-crossing.
-- now try to find another bend in this line that crosses this one.
p0 = st_pointn(bends[i], 1);
p1 = st_pointn(bends[i], -1);
--this = st_makeline(st_pointn(bends[i], 1), st_pointn(bends[i], -1));
-- go through each bend in this line, and see if has a potential to cross bends[i].
-- optimization: we care only about bends which beginning and end start at different
-- sides of the plane, separated by endpoints p0 and p1.
for j in 1..array_length(bends, 1) loop
continue when i = j;
p2 = st_pointn(bends[j], 1);
p3 = st_pointn(bends[j], -1);
-- https://stackoverflow.com/questions/1560492
s2 = (st_x(p0)-st_x(p1)*(st_y(p2)-st_y(p1))-(st_y(p0)-st_y(p1))*(st_x(p2)-st_x(p1)));
s3 = (st_x(p0)-st_x(p1)*(st_y(p3)-st_y(p1))-(st_y(p0)-st_y(p1))*(st_x(p3)-st_x(p1)));
continue when sign(s2) = sign(s3);
-- bend j may be crossing bend i, and it has a chance to be "important" --
-- p2 and p3 are in different sides of the plane as delimited by p0 and p1.
-- now does it really cross the line (p0, p1)?
end loop;
end if;
end loop;
end