eliminate small bends and reduce isolation_threshold

too many bends get "isolated". The criteria needs to be updated, for now
just reducing the threshold improves the situation a bit.

IV/visuals.sql

@@ -68,6 +68,7 @@ end $$ language plpgsql;
 
 delete from wm_visuals where name like 'salvis%';
 insert into wm_visuals(name, way) values('salvis', (
+    with multismall as (
       select st_intersection(
         (select st_union(way) from wm_rivers where name in ('Šalčia', 'Visinčia')),
         wm_bbox(
@@ -77,7 +78,13 @@ insert into wm_visuals(name, way) values('salvis', (
           ),
           :scaledwidth
         )
+      ) ways
     )
+    -- protecting against very small bends that were cut
+    -- in the corner of the picture
+    select st_union(a.geom)
+    from st_dump((select ways from multismall)) a
+    where st_length(a.geom) >= 100
 ));
 
 do $$
@@ -110,7 +117,7 @@ begin
   foreach i in array array[16, 64, 256] loop
     geom1 = st_simplify((select way from wm_visuals where name='salvis'), i);
     geom2 = st_simplifyvw((select way from wm_visuals where name='salvis'), i*i);
-    geom3 = st_simplifywm((select way from wm_visuals where name='salvis'), i);
+    geom3 = st_simplifywm((select way from wm_visuals where name='salvis'), i, 50, 'salvis-' || i);
     insert into wm_visuals(name, way) values
       ('salvis-douglas-'     || i, geom1),
       ('salvis-douglas-'     || i || '-chaikin', st_chaikinsmoothing(geom1, 5)),

IV/wm.sql

@@ -335,7 +335,7 @@ create function wm_bend_attrs(
   dbggen integer default null
 ) returns wm_t_attrs[] as $$
 declare
-  isolation_threshold constant real default 0.5;
+  isolation_threshold constant real default 0.3;
   attrs wm_t_attrs[];
   attr wm_t_attrs;
   bend geometry;