Simplify geometry
Configuration examples Simplify geometry
The script presents an example how you can simplify the geometry of a polygon. It will delete convex points from the geometry. Compare it with putting a rubber band around the shape, see also convex hull
To what extent the simplifying is executed depends on the amount of iterations implemented.
Tip: use the sequence2points function and take the maximum value for ordinal, you'll get the maximum amount of points for a single polygon. This is the theoretical maximum amount of iterations necessary.
Since GeoDMS version 7.408 you can use the bg_simplify_polygon function to simplify a polygon and since 8.031 the bg_simplify_linestring function to simplify an arc.
We advice to use these functions, the following example can still be used but is not advised.
container Simplified := Simplify(iter_domain, 50); // domain and number of iterations template Simplify { // begin case parameters unit<uint32> iter_domain; parameter<uint32> nrIterations; // end case parameters unit<uint32> iter := range(uint32, 0, nrIterations) { attribute<string> name := 'I' + string(id(.)); attribute<string> PrevName := MakeDefined(name[id(.)-1], 'StartingState'); }
container StartingState { unit<uint32> NextValue := sequence2points(iter_domain/geometry_rd); }
container Iters := for_each_ne(Iter/name, 'IterT('+Iter/PrevName+', iter_domain)'); container LastIterI := =last('Iters/'+Iter/name); template IterT { <I>// begin case parameters</I> container PrevIterator; unit<uint32> domain; <I>// end case parameters</I>
unit<uint32> PrevValue := PrevIterator/NextValue; container ConvexHullT := MakeConvexHullT(domain, PrevValue); unit<uint32> NextValue := ConvexHullT/sequence/Convex_hull_points; }
container MakeFinal { unit <uint32> domain_with_endpoints := union_unit(iter_domain, LastIter/NextValue) { attribute<geometries/rdc> point := union_data(., LastIter/NextValue/point, first(LastIter/NextValue/point, LastIter/NextValue/SequenceNr)); attribute<uint32> SequenceNr := union_data(., LastIter/NextValue/SequenceNr, ID(Iteratie_domain)); } attribute<geometries/rdc> convex_hull (iter_domain, poly) := points2sequence(domain_with_endpoints /point, domain_with_endpoints /SequenceNr); } template MakeConvexHullT { <I>// begin case parameters</I> unit<uint32> domain; unit<uint32> seq; <I>// end case parameters</I>
unit<uint32> sequence := seq { attribute<geometries/rdc> point := seq/point; attribute<uint32> SequenceNr := seq/SequenceNr;
attribute<uint32> min_index (domain) := min_index(id(.), SequenceNr); attribute<uint32> max_index (domain) := max_index(id(.), SequenceNr);
attribute<bool> IsFirst := id(.) == min_index[SequenceNr]; attribute<bool> IsLast := id(.) == max_index[SequenceNr]; attribute<uint32> prev_id := IsFirst ? rjoin(SequenceNr, id(domain), max_index) : ID(.)-1; attribute<uint32> next_id := Islast ? rjoin(SequenceNr, id(domain), min_index) : ID(.)+1; attribute<geometries/rdc> A := point[prev_id]; attribute<geometries/rdc> B := point; attribute<geometries/rdc> C := point[next_id]; attribute<geometries/rdc> p := B - A; attribute<geometries/rdc> q := C - B;
attribute<float32> Px := pointcol(P); attribute<float32> Py := pointrow(P); attribute<float32> Qx := pointcol(Q); attribute<float32> Qy := pointrow(Q); attribute<float32> det := PxQy - PyQx; unit<uint32> Convex_hull_points := subset(det <= 0f && (point != rjoin(prev_id, id(.), point))) { attribute<geometries/rdc> point := ../point[nr_OrgEntity]; attribute<uint32> SequenceNr := ../SequenceNr[nr_OrgEntity]; } } } }
