commit 1a4be957e3e459e85dbd8665f6316a9ff36ac2c2 (tree)
parent b613a78fa59c9c382538e4e60c9edaa3a2632ae1
Author: Motiejus Jakštys <motiejus@jakstys.lt>
Date: Wed, 19 May 2021 22:57:49 +0300
Adaptive bend exaggeration
Diffstat:
| M | test.sql | | | 3 | ++- |
| M | wm.sql | | | 218 | +++++++++++++++++++++++++++++++++++++++++++------------------------------------ |
2 files changed, 120 insertions(+), 101 deletions(-)
diff --git a/test.sql b/test.sql
@@ -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 $$ language plpgsql;
diff --git a/wm.sql b/wm.sql
@@ -331,6 +331,7 @@ drop function if exists wm_bend_attrs;
drop function if exists wm_isolated_bends;
drop function if exists wm_elimination;
drop function if exists wm_exaggeration;
+drop function if exists wm_st_intersects_neighbors;
drop type if exists wm_t_bend_attrs;
create type wm_t_bend_attrs as (
bend geometry,
@@ -401,11 +402,7 @@ end $$ 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
@@ -413,41 +410,35 @@ 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:
- -- 1. draw a line between midpoint and the point on the bend.
- -- 2. multiply the line length by M. Midpoint stays intact.
- -- 3. the new set of lines form a new bend.
- -- Uses linear interpolation; can be updated to gaussian or similar;
- -- then interpolate manually instead of relying on st_addmeasure.
- bendm = st_collect(
- st_addmeasure(st_geometryn(splitbend, 1), 1, scale),
- st_addmeasure(st_geometryn(splitbend, 2), scale, 1)
- );
-
- points = array((
- select st_scale(
- st_makepoint(st_x(geom), st_y(geom)),
- st_makepoint(st_m(geom), st_m(geom)),
- midpoint
- )
- from st_dumppoints(bendm)
- order by path[1], path[2]
- ));
-
- bend = st_setsrid(st_makeline(points), st_srid(bend));
- size = wm_adjsize(bend);
- end 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:
+ -- 1. draw a line between midpoint and the point on the bend.
+ -- 2. multiply the line length by M. Midpoint stays intact.
+ -- 3. the new set of lines form a new bend.
+ -- Uses linear interpolation; can be updated to gaussian or similar;
+ -- then interpolate manually instead of relying on st_addmeasure.
+ bendm = st_collect(
+ st_addmeasure(st_geometryn(splitbend, 1), 1, scale),
+ st_addmeasure(st_geometryn(splitbend, 2), scale, 1)
+ );
+
+ points = array((
+ select st_scale(
+ st_makepoint(st_x(geom), st_y(geom)),
+ st_makepoint(st_m(geom), st_m(geom)),
+ midpoint
+ )
+ from st_dumppoints(bendm)
+ order by path[1], path[2]
+ ));
+
+ bend = st_setsrid(st_makeline(points), st_srid(bend));
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(
@@ -489,80 +529,57 @@ 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;
+ this_mutated = true;
+ bendattrs[i] = tmpbendattr;
+ size = wm_adjsize(bendattrs[i].bend);
+ end loop;
+ continue when not this_mutated;
- continue bendloop when st_intersects(tmpbendattr.bend, tmpint);
- end loop;
+ mutated = true;
- -- No intersections within intersect_patience, mutate bend!
- mutated = true;
- bendattrs[i] = tmpbendattr;
+ -- 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.
+ tmpbendattr.bend = st_removepoint(
+ bendattrs[i-1].bend,
+ st_npoints(bendattrs[i-1].bend)-1
+ );
+ bendattrs[i-1] = tmpbendattr;
+ tmpbendattr.bend = st_removepoint(bendattrs[i+1].bend, 0);
+ bendattrs[i+1] = tmpbendattr;
- -- 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.
- tmpbendattr.bend = st_removepoint(
- bendattrs[i-1].bend,
- st_npoints(bendattrs[i-1].bend)-1
+ if dbgname is not null then
+ insert into wm_debug (stage, name, gen, nbend, way) values(
+ 'gexaggeration', dbgname, dbggen, i, bendattrs[i].bend
);
- bendattrs[i-1] = tmpbendattr;
- tmpbendattr.bend = st_removepoint(bendattrs[i+1].bend, 0);
- bendattrs[i+1] = tmpbendattr;
-
- if dbgname is not null then
- insert into wm_debug (stage, name, gen, nbend, way) values(
- '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
