Adaptive bend exaggeration
Motiejus Jakštys
parent
b613a78fa5
commit
1a4be957e3
3
test.sql
3
test.sql
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@ -190,6 +190,7 @@ declare
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begin
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select way from wm_debug where name='fig3' and stage='bbends' and gen=1 and nbend=2 into fig3b2;
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size = wm_adjsize(fig3b2);
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bend = wm_exaggerate_bend(fig3b2, size, 50.);
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bend = wm_exaggerate_bend(fig3b2);
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perform assert_equals('ST_LineString', st_geometrytype(bend));
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insert into wm_debug(stage, name, gen, nbend, way) values('manual', 'fig3', 1, 1, bend);
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end $$ language plpgsql;
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216
wm.sql
216
wm.sql
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@ -331,6 +331,7 @@ drop function if exists wm_bend_attrs;
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drop function if exists wm_isolated_bends;
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drop function if exists wm_elimination;
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drop function if exists wm_exaggeration;
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drop function if exists wm_st_intersects_neighbors;
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drop type if exists wm_t_bend_attrs;
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create type wm_t_bend_attrs as (
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bend geometry,
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@ -401,11 +402,7 @@ end $$ language plpgsql;
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-- wm_exaggerate_bend exaggerates a given bend. Must be a simple linestring.
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drop function if exists wm_exaggerate_bend;
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create function wm_exaggerate_bend(
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INOUT bend geometry,
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size float,
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desired_size float
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) as $$
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create function wm_exaggerate_bend(INOUT bend geometry) as $$
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declare
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scale constant float default 2; -- per-step scaling factor
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midpoint geometry; -- midpoint of the baseline
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@ -413,41 +410,35 @@ declare
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bendm geometry; -- bend with coefficients to prolong the lines
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points geometry[];
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begin
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if size = 0 then
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raise 'invalid input: zero-area bend';
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end if;
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midpoint = st_lineinterpolatepoint(st_makeline(
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st_pointn(bend, 1),
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st_pointn(bend, -1)
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), .5);
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while size < desired_size loop
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splitbend = wm_st_split(bend, st_lineinterpolatepoint(bend, .5));
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-- Convert bend to LINESTRINGM, where M is the fraction by how
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-- much the point will be prolonged:
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-- 1. draw a line between midpoint and the point on the bend.
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-- 2. multiply the line length by M. Midpoint stays intact.
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-- 3. the new set of lines form a new bend.
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-- Uses linear interpolation; can be updated to gaussian or similar;
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-- then interpolate manually instead of relying on st_addmeasure.
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bendm = st_collect(
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st_addmeasure(st_geometryn(splitbend, 1), 1, scale),
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st_addmeasure(st_geometryn(splitbend, 2), scale, 1)
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);
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splitbend = wm_st_split(bend, st_lineinterpolatepoint(bend, .5));
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-- Convert bend to LINESTRINGM, where M is the fraction by how
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-- much the point will be prolonged:
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-- 1. draw a line between midpoint and the point on the bend.
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-- 2. multiply the line length by M. Midpoint stays intact.
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-- 3. the new set of lines form a new bend.
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-- Uses linear interpolation; can be updated to gaussian or similar;
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-- then interpolate manually instead of relying on st_addmeasure.
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bendm = st_collect(
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st_addmeasure(st_geometryn(splitbend, 1), 1, scale),
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st_addmeasure(st_geometryn(splitbend, 2), scale, 1)
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);
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points = array((
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select st_scale(
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st_makepoint(st_x(geom), st_y(geom)),
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st_makepoint(st_m(geom), st_m(geom)),
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midpoint
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)
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from st_dumppoints(bendm)
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order by path[1], path[2]
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));
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points = array((
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select st_scale(
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st_makepoint(st_x(geom), st_y(geom)),
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st_makepoint(st_m(geom), st_m(geom)),
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midpoint
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)
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from st_dumppoints(bendm)
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order by path[1], path[2]
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));
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bend = st_setsrid(st_makeline(points), st_srid(bend));
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size = wm_adjsize(bend);
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end loop;
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bend = st_setsrid(st_makeline(points), st_srid(bend));
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end
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$$ language plpgsql;
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@ -474,8 +465,57 @@ begin
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if cmp > 0 then
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adjsize = (area*(0.75/cmp));
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end if;
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end
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$$ language plpgsql;
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end $$ language plpgsql;
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drop function if exists wm_st_intersects_neighbors;
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create function wm_st_intersects_neighbors(
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bendattrs wm_t_bend_attrs[],
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bend geometry,
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i integer,
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intersect_patience integer
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) returns boolean as $$
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declare
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n integer;
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neighbor geometry;
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begin
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-- Do close-by bends intersect with this one? Special
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-- handling first, because 2 vertices need to be removed before checking.
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n = st_npoints(bendattrs[i-1].bend);
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if n > 3 and st_intersects(bend,
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st_removepoint(st_removepoint(bendattrs[i-1].bend, n-1), n-2)) then
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return true;
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end if;
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n = st_npoints(bendattrs[i+1].bend);
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if n > 3 and st_intersects(bend,
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st_removepoint(st_removepoint(bendattrs[i+1].bend, 0), 0)) then
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return true;
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end if;
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-- Go through all the neighbors and see if the enlarged bend intersects
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-- with any of them. If yes -- abort enlargement.
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for n in -intersect_patience+1..intersect_patience-1 loop
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continue when i+n < 1 or n in (-1, 0, 1);
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continue when i+n > array_length(bendattrs, 1);
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-- More special handling: if the neigbhoring bend has 3 vertices, the
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-- neighbor's neighbor may just touch the tmpbendattr.bend; in this
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-- case, the nearest vertex should be removed before comparing.
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neighbor = bendattrs[i+n].bend;
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if st_npoints(neighbor) > 2 then
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if n = -2 and st_npoints(bendattrs[i+n+1].bend) = 3 then
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neighbor = st_removepoint(neighbor, st_npoints(neighbor)-1);
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elsif n = 2 and st_npoints(bendattrs[i+n-1].bend) = 3 then
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neighbor = st_removepoint(neighbor, 0);
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end if;
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end if;
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if st_intersects(bend, neighbor) then
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return true;
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end if;
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end loop;
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return false;
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end $$ language plpgsql;
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-- wm_exaggeration is the Exaggeration Operator described in the WM paper.
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create function wm_exaggeration(
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@ -489,80 +529,57 @@ create function wm_exaggeration(
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declare
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desired_size constant float default pi()*(dhalfcircle^2)/8;
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tmpbendattr wm_t_bend_attrs;
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tmpint geometry;
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neighbor geometry;
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size float;
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i integer;
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n integer;
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last_id integer;
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this_mutated boolean;
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begin
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mutated = false;
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<<bendloop>>
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for i in 1..array_length(bendattrs, 1) loop
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if bendattrs[i].isolated and bendattrs[i].adjsize < desired_size then
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tmpbendattr.bend = wm_exaggerate_bend(
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bendattrs[i].bend,
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bendattrs[i].adjsize,
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desired_size
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continue when not bendattrs[i].isolated;
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size = bendattrs[i].adjsize;
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this_mutated = false;
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-- keep increasing this bend until either size permits, or it hits a
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-- neighboring bend (intersect_patience number of neighbors will be
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-- checked). When the size is right, stick it to the line.
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while size < desired_size loop
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tmpbendattr.bend = wm_exaggerate_bend(bendattrs[i].bend);
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exit when wm_st_intersects_neighbors(
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bendattrs,
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tmpbendattr.bend,
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i,
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intersect_patience
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);
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-- does tmpbendattrs.bend intersect with the previous or next
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-- intersect_patience bends? If they do, abort exaggeration for this one.
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-- Do close-by bends intersect with this one? Special
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-- handling first, because 2 vertices need to be removed before checking.
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n = st_npoints(bendattrs[i-1].bend);
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if n > 3 then
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continue when st_intersects(tmpbendattr.bend,
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st_removepoint(st_removepoint(bendattrs[i-1].bend, n-1), n-2));
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end if;
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n = st_npoints(bendattrs[i+1].bend);
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if n > 3 then
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continue when st_intersects(tmpbendattr.bend,
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st_removepoint(st_removepoint(bendattrs[i+1].bend, 0), 0));
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end if;
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for n in -intersect_patience+1..intersect_patience-1 loop
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continue when n in (-1, 0, 1);
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continue when i+n < 1;
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continue when i+n > array_length(bendattrs, 1);
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-- More special handling: if the neigbhoring bend has 3 vertices, the
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-- neighbor's neighbor may just touch the tmpbendattr.bend; in this
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-- case, the nearest vertex should be removed before comparing.
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tmpint = bendattrs[i+n].bend;
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if st_npoints(tmpint) > 2 then
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if n = -2 and st_npoints(bendattrs[i+n+1].bend) = 3 then
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tmpint = st_removepoint(tmpint, st_npoints(tmpint)-1);
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elsif n = 2 and st_npoints(bendattrs[i+n-1].bend) = 3 then
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tmpint = st_removepoint(tmpint, 0);
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end if;
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end if;
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continue bendloop when st_intersects(tmpbendattr.bend, tmpint);
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end loop;
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-- No intersections within intersect_patience, mutate bend!
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mutated = true;
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this_mutated = true;
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bendattrs[i] = tmpbendattr;
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size = wm_adjsize(bendattrs[i].bend);
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end loop;
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continue when not this_mutated;
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-- remove last vertex of the previous bend and first vertex of the next
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-- bend, because bends always share a line segment together this is
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-- duplicated in a few places, because PostGIS does not allow (?)
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-- mutating an array when passed to a function.
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tmpbendattr.bend = st_removepoint(
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bendattrs[i-1].bend,
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st_npoints(bendattrs[i-1].bend)-1
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mutated = true;
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-- Stick the right-sized bend to the line
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-----------------------------------------
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-- Remove last vertex of the previous bend and first vertex of the next
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-- bend, because bends always share a line segment together this is
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-- duplicated in a few places, because PostGIS does not allow (?)
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-- mutating an array when passed to a function.
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tmpbendattr.bend = st_removepoint(
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bendattrs[i-1].bend,
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st_npoints(bendattrs[i-1].bend)-1
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);
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bendattrs[i-1] = tmpbendattr;
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tmpbendattr.bend = st_removepoint(bendattrs[i+1].bend, 0);
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bendattrs[i+1] = tmpbendattr;
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if dbgname is not null then
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insert into wm_debug (stage, name, gen, nbend, way) values(
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'gexaggeration', dbgname, dbggen, i, bendattrs[i].bend
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);
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bendattrs[i-1] = tmpbendattr;
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tmpbendattr.bend = st_removepoint(bendattrs[i+1].bend, 0);
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bendattrs[i+1] = tmpbendattr;
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if dbgname is not null then
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insert into wm_debug (stage, name, gen, nbend, way) values(
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'gexaggeration', dbgname, dbggen, i, bendattrs[i].bend
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);
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end if;
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end if;
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end loop;
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end $$ language plpgsql;
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@ -799,7 +816,8 @@ begin
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end loop;
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lines[i] = st_linemerge(st_union(bends));
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if st_geometrytype(lines[i]) != 'ST_LineString' then
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-- For manual debugging:
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-- For manual debugging, usually when wm_exaggeration returns
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-- ST_MultiLineString. Uncomment the code below and `raise notice`.
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--insert into wm_manual(name, way)
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--select 'non-linestring-' || a.path[1], a.geom
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--from st_dump(lines[i]) a
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