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Motiejus Jakštys 2021-03-10 15:56:08 +02:00
parent 8159124a48
commit 44e5352c16
1 changed files with 25 additions and 16 deletions
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41
IV/wm.sql
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@ -1,9 +1,9 @@
\set ON_ERROR_STOP on
SET plpgsql.extra_errors TO 'all';
-- detect_bends detects bends using the inflection angles. No corrections.
drop function if exists detect_bends;
-- detect_bends detects bends using the inflection angles. It does not do corrections.
create or replace function detect_bends(line geometry, OUT bends geometry[]) as $$
create function detect_bends(line geometry, OUT bends geometry[]) as $$
declare
pi real;
p geometry;
@ -16,8 +16,8 @@ declare
begin
pi = radians(180);
-- the last vertex is iterated over twice, because the algorithm uses 3 vertices
-- to calculate the angle between them.
-- 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:
--
@ -97,7 +97,8 @@ $$ language plpgsql;
-- fix_gentle_inflections1 fixes gentle inflections of an array of lines in
-- one direction. This is an implementation detail of fix_gentle_inflections.
create or replace function fix_gentle_inflections1(INOUT bends geometry[]) as $$
drop function if exists fix_gentle_inflections1;
create function fix_gentle_inflections1(INOUT bends geometry[]) as $$
declare
pi real;
small_angle real;
@ -145,13 +146,14 @@ begin
-- if the bend got too short, stop processing it
exit when array_length(phead, 1) < 3;
-- if inflection angle between ptail[1:3] "large", stop processing this bend
-- inflection angle between ptail[1:3] is "large", stop processing
exit when abs(st_angle(phead[1], phead[2], phead[3]) - pi) > small_angle;
-- distance from head's first vertex should be larger than from second vertex
-- distance from head's 1st vertex should be larger than from 2nd vertex
exit when st_distance(ptail, phead[2]) < st_distance(ptail, phead[3]);
-- detected a gentle inflection. Move head of the tail to the tail of head
-- Detected a gentle inflection.
-- Move head of the tail to the tail of head
bends[i] = st_removepoint(bends[i], 0);
bends[i-1] = st_addpoint(bends[i-1], phead[3]);
end loop;
@ -162,7 +164,8 @@ $$ language plpgsql;
-- self_crossing eliminates self-crossing from the bends, following the
-- article's section "Self-line Crossing When Cutting a Bend".
create or replace function self_crossing(INOUT bends geometry[]) as $$
drop function if exists self_crossing;
create function self_crossing(INOUT bends geometry[]) as $$
declare
i int4;
j int4;
@ -189,7 +192,9 @@ begin
p1 = null;
p2 = null;
p3 = null;
for p0 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 = p0;
@ -219,8 +224,10 @@ begin
-- are p2 and p3 on the different sides of line(p0,p1)? vector
-- multiplication; 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)));
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);
-- do end vertices of bend[i] cross bend[j]?
@ -228,12 +235,13 @@ begin
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));
continue when st_numgeometries(multi) = 2 and
(st_contains(bends[j], a) or st_contains(bends[j], b));
-- real self-crossing detected! Remove it.
-- if j < i:
-- bends[j] = multi[1][1...n-1]; that will have all the vertices of bends[j],
-- except the crossing and what comes after it.
-- bends[j] = multi[1][1...n-1]; that will have all the vertices of
-- bends[j], except the crossing and what comes after it.
-- bends[j] = append(bends[j], bends[i][-1])
-- remove bends from bends[j+1] to bends[i] inclusive.
-- j := i+1
@ -253,7 +261,8 @@ begin
prev_length = array_length(bends, 1);
if j < i then
bends[j] = st_geometryn(multi, 1);
bends[j] = st_setpoint(bends[j], st_npoints(bends[j])-1, st_pointn(bends[i], st_npoints(bends[i])));
bends[j] = st_setpoint(bends[j], st_npoints(bends[j])-1,
st_pointn(bends[i], st_npoints(bends[i])));
bends = bends[1:j] || bends[i+1:prev_length];
j = i;
else