Turning line segments in to arcs, pretty transport display - line

Question

I am trying to turn a line segment display
in to arc segment display
My linput data is encoded as a series of MultiLineString geometries,
I have tried things like st_forcecurve(st_linemerge(geom)) which turns my data in to series of very nice straight lines encoded as CompoundCurve geometries. Its there any way to acutal generate a curved line instead off a straight line.

Answer 1

It seems I am not the only one that has run in to issues like this A very similair problem
One of the answers did what I wanted. I just converted that answer in to an psql function that generates a curved arc, using a factor for how curved you want the answer, low values very curvy, high values a stright line.
--
-- Draw an arc geom between two differentlocations
--
-- point1 must be a point starting location
-- point2 must be a point ending location
-- arc_fractor how curved you want the result
-- returns a curved geometry
create or replace function mk_arg_geom(point1 geometry, point2 geometry, arc_factor integer )
returns geometry
as $$
DECLARE
ret geometry;
ret_srid integer;
tmp_geom geometry;
c_geom geometry;
BEGIN
ret := null;
ret_srid:=st_srid(point1);
tmp_geom=st_makeline(point1,point2);
c_geom:= ST_CurveToLine('CIRCULARSTRING(' ||
st_x(st_startpoint(tmp_geom)) ||
' ' ||
st_y(st_startpoint(tmp_geom)) ||
', ' ||
st_x(st_centroid(ST_OffsetCurve(tmp_geom, st_length(tmp_geom)/arc_factor, 'quad_segs=4 join=bevel'))) ||
' ' ||
st_y(st_centroid(ST_OffsetCurve(tmp_geom, st_length(tmp_geom)/arc_factor, 'quad_segs=4 join=bevel'))) ||
', ' ||
st_x(st_endpoint(tmp_geom)) ||
' ' ||
st_y(st_endpoint(tmp_geom))
|| ')');
ret=st_setsrid(c_geom,ret_srid);
return ret;
END;
$$
LANGUAGE plpgsql;