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Adaptive bend exaggeration

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Motiejus Jakštys 2021-05-19 22:57:49 +03:00 committed by Motiejus Jakštys
parent b613a78fa5
commit 1a4be957e3
2 changed files with 119 additions and 100 deletions
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3
test.sql
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@ -190,6 +190,7 @@ declare
begin
select way from wm_debug where name='fig3' and stage='bbends' and gen=1 and nbend=2 into fig3b2;
size = wm_adjsize(fig3b2);
bend = wm_exaggerate_bend(fig3b2, size, 50.);
bend = wm_exaggerate_bend(fig3b2);
perform assert_equals('ST_LineString', st_geometrytype(bend));
insert into wm_debug(stage, name, gen, nbend, way) values('manual', 'fig3', 1, 1, bend);
end $$ language plpgsql;

144
wm.sql
View File

@ -331,6 +331,7 @@ drop function if exists wm_bend_attrs;
drop function if exists wm_isolated_bends;
drop function if exists wm_elimination;
drop function if exists wm_exaggeration;
drop function if exists wm_st_intersects_neighbors;
drop type if exists wm_t_bend_attrs;
create type wm_t_bend_attrs as (
bend geometry,
@ -401,11 +402,7 @@ end $$ language plpgsql;
-- wm_exaggerate_bend exaggerates a given bend. Must be a simple linestring.
drop function if exists wm_exaggerate_bend;
create function wm_exaggerate_bend(
INOUT bend geometry,
size float,
desired_size float
) as $$
create function wm_exaggerate_bend(INOUT bend geometry) as $$
declare
scale constant float default 2; -- per-step scaling factor
midpoint geometry; -- midpoint of the baseline
@ -413,15 +410,11 @@ declare
bendm geometry; -- bend with coefficients to prolong the lines
points geometry[];
begin
if size = 0 then
raise 'invalid input: zero-area bend';
end if;
midpoint = st_lineinterpolatepoint(st_makeline(
st_pointn(bend, 1),
st_pointn(bend, -1)
), .5);
while size < desired_size loop
splitbend = wm_st_split(bend, st_lineinterpolatepoint(bend, .5));
-- Convert bend to LINESTRINGM, where M is the fraction by how
-- much the point will be prolonged:
@ -446,8 +439,6 @@ begin
));
bend = st_setsrid(st_makeline(points), st_srid(bend));
size = wm_adjsize(bend);
end loop;
end
$$ language plpgsql;
@ -474,8 +465,57 @@ begin
if cmp > 0 then
adjsize = (area*(0.75/cmp));
end if;
end
$$ language plpgsql;
end $$ language plpgsql;
drop function if exists wm_st_intersects_neighbors;
create function wm_st_intersects_neighbors(
bendattrs wm_t_bend_attrs[],
bend geometry,
i integer,
intersect_patience integer
) returns boolean as $$
declare
n integer;
neighbor geometry;
begin
-- Do close-by bends intersect with this one? Special
-- handling first, because 2 vertices need to be removed before checking.
n = st_npoints(bendattrs[i-1].bend);
if n > 3 and st_intersects(bend,
st_removepoint(st_removepoint(bendattrs[i-1].bend, n-1), n-2)) then
return true;
end if;
n = st_npoints(bendattrs[i+1].bend);
if n > 3 and st_intersects(bend,
st_removepoint(st_removepoint(bendattrs[i+1].bend, 0), 0)) then
return true;
end if;
-- Go through all the neighbors and see if the enlarged bend intersects
-- with any of them. If yes -- abort enlargement.
for n in -intersect_patience+1..intersect_patience-1 loop
continue when i+n < 1 or n in (-1, 0, 1);
continue when i+n > array_length(bendattrs, 1);
-- More special handling: if the neigbhoring bend has 3 vertices, the
-- neighbor's neighbor may just touch the tmpbendattr.bend; in this
-- case, the nearest vertex should be removed before comparing.
neighbor = bendattrs[i+n].bend;
if st_npoints(neighbor) > 2 then
if n = -2 and st_npoints(bendattrs[i+n+1].bend) = 3 then
neighbor = st_removepoint(neighbor, st_npoints(neighbor)-1);
elsif n = 2 and st_npoints(bendattrs[i+n-1].bend) = 3 then
neighbor = st_removepoint(neighbor, 0);
end if;
end if;
if st_intersects(bend, neighbor) then
return true;
end if;
end loop;
return false;
end $$ language plpgsql;
-- wm_exaggeration is the Exaggeration Operator described in the WM paper.
create function wm_exaggeration(
@ -489,64 +529,42 @@ create function wm_exaggeration(
declare
desired_size constant float default pi()*(dhalfcircle^2)/8;
tmpbendattr wm_t_bend_attrs;
tmpint geometry;
neighbor geometry;
size float;
i integer;
n integer;
last_id integer;
this_mutated boolean;
begin
mutated = false;
<<bendloop>>
for i in 1..array_length(bendattrs, 1) loop
if bendattrs[i].isolated and bendattrs[i].adjsize < desired_size then
tmpbendattr.bend = wm_exaggerate_bend(
bendattrs[i].bend,
bendattrs[i].adjsize,
desired_size
continue when not bendattrs[i].isolated;
size = bendattrs[i].adjsize;
this_mutated = false;
-- keep increasing this bend until either size permits, or it hits a
-- neighboring bend (intersect_patience number of neighbors will be
-- checked). When the size is right, stick it to the line.
while size < desired_size loop
tmpbendattr.bend = wm_exaggerate_bend(bendattrs[i].bend);
exit when wm_st_intersects_neighbors(
bendattrs,
tmpbendattr.bend,
i,
intersect_patience
);
-- does tmpbendattrs.bend intersect with the previous or next
-- intersect_patience bends? If they do, abort exaggeration for this one.
-- Do close-by bends intersect with this one? Special
-- handling first, because 2 vertices need to be removed before checking.
n = st_npoints(bendattrs[i-1].bend);
if n > 3 then
continue when st_intersects(tmpbendattr.bend,
st_removepoint(st_removepoint(bendattrs[i-1].bend, n-1), n-2));
end if;
n = st_npoints(bendattrs[i+1].bend);
if n > 3 then
continue when st_intersects(tmpbendattr.bend,
st_removepoint(st_removepoint(bendattrs[i+1].bend, 0), 0));
end if;
for n in -intersect_patience+1..intersect_patience-1 loop
continue when n in (-1, 0, 1);
continue when i+n < 1;
continue when i+n > array_length(bendattrs, 1);
-- More special handling: if the neigbhoring bend has 3 vertices, the
-- neighbor's neighbor may just touch the tmpbendattr.bend; in this
-- case, the nearest vertex should be removed before comparing.
tmpint = bendattrs[i+n].bend;
if st_npoints(tmpint) > 2 then
if n = -2 and st_npoints(bendattrs[i+n+1].bend) = 3 then
tmpint = st_removepoint(tmpint, st_npoints(tmpint)-1);
elsif n = 2 and st_npoints(bendattrs[i+n-1].bend) = 3 then
tmpint = st_removepoint(tmpint, 0);
end if;
end if;
continue bendloop when st_intersects(tmpbendattr.bend, tmpint);
end loop;
-- No intersections within intersect_patience, mutate bend!
mutated = true;
this_mutated = true;
bendattrs[i] = tmpbendattr;
size = wm_adjsize(bendattrs[i].bend);
end loop;
continue when not this_mutated;
-- remove last vertex of the previous bend and first vertex of the next
mutated = true;
-- Stick the right-sized bend to the line
-----------------------------------------
-- Remove last vertex of the previous bend and first vertex of the next
-- bend, because bends always share a line segment together this is
-- duplicated in a few places, because PostGIS does not allow (?)
-- mutating an array when passed to a function.
@ -563,7 +581,6 @@ begin
'gexaggeration', dbgname, dbggen, i, bendattrs[i].bend
);
end if;
end if;
end loop;
end $$ language plpgsql;
@ -799,7 +816,8 @@ begin
end loop;
lines[i] = st_linemerge(st_union(bends));
if st_geometrytype(lines[i]) != 'ST_LineString' then
-- For manual debugging:
-- For manual debugging, usually when wm_exaggeration returns
-- ST_MultiLineString. Uncomment the code below and `raise notice`.
--insert into wm_manual(name, way)
--select 'non-linestring-' || a.path[1], a.geom
--from st_dump(lines[i]) a