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inflections now work

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Motiejus Jakštys 2021-05-19 22:57:45 +03:00 committed by Motiejus Jakštys
parent 87651369c8
commit fab653ee3a
2 changed files with 13 additions and 21 deletions
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1
tests.sql
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@ -47,7 +47,6 @@ begin
drop table if exists inflections;
create table inflections (way geometry);
--insert into inflections select unnest(fix_gentle_inflections(vbends));
insert into inflections select unnest(fix_gentle_inflections(vbends));
end $$ language plpgsql;

33
wm.sql
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@ -44,7 +44,7 @@ begin
if p3 is null then
continue;
end if;
cur_sign = sign(pi - st_angle(p1, p2, p2, p3));
cur_sign = sign(pi - st_angle(p1, p2, p3));
if bend is null then
bend = st_makeline(p3, p2);
@ -78,8 +78,8 @@ create or replace function fix_gentle_inflections(INOUT bends geometry[]) as $$
declare
pi real;
small_angle real;
phead geometry; -- head point of head bend
ptail geometry[]; -- 3 head points of tail bend
ptail geometry; -- tail point of tail bend
phead geometry[]; -- 3 tail points of head bend
i int4; -- bends[i] is the current head
begin
pi = radians(180);
@ -87,12 +87,7 @@ begin
-- be joined
small_angle := radians(30);
<<bend_loop>>
for i in select generate_subscripts(bends, 1) loop
if i = 1 then
continue;
end if;
for i in 2..array_length(bends, 1) loop
-- Predicate: two bends will always share an edge. Assuming (A,B,C,D,E,F)
-- is a bend:
-- C________D
@ -115,24 +110,22 @@ begin
-- After processing the curve following the definition of a bend, the bend
-- [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].
select geom from st_dumppoints(bends[i]) order by path[1] desc limit 1 into phead;
select geom from st_dumppoints(bends[i-1]) order by path[1] asc limit 1 into ptail;
while true loop
-- copy last 3 points of bends[i-1] (tail) to ptail
select array(select geom from st_dumppoints(bends[i-1]) order by path[1] desc limit 3) into ptail;
select array(
select geom from st_dumppoints(bends[i]) order by path[1] asc limit 3
) into phead;
-- if inflection angle between ptail[1:3] "large", stop processing this bend
if abs(st_angle(ptail[1], ptail[2], ptail[2], ptail[3]) - pi) > small_angle then
exit bend_loop;
end if;
exit when abs(st_angle(phead[1], phead[2], phead[3]) - pi) > small_angle;
-- distance from last vertex should be larger than second-last vertex
if st_distance(phead, ptail[2]) < st_distance(phead, ptail[3]) then
exit bend_loop;
end if;
-- distance from head's first vertex should be larger than from second vertex
exit when st_distance(ptail, phead[2]) < st_distance(ptail, phead[3]);
-- detected a gentle inflection. Move head of the tail to the tail of head
bends[i] = st_addpoint(bends[i], ptail[3]);
bends[i-1] = st_removepoint(bends[i-1], st_npoints(bends[i-1])-1);
bends[i] = st_removepoint(bends[i], 0);
bends[i-1] = st_addpoint(bends[i-1], phead[3]);
end loop;
end loop;