# HG changeset patch
# User Sascha L. Teichmann <sascha.teichmann@intevation.de>
# Date 1570614633 -7200
# Node ID 680f1d8802f0c388196cc1201c75eb2048ab155b
# Parent  f456ce0a6a0ec6e73f77a2a780120e863f8f5561
STRTree: Add a builder that ignores triangles which are filtered out before.

diff -r f456ce0a6a0e -r 680f1d8802f0 pkg/octree/strtree.go
--- a/pkg/octree/strtree.go	Wed Oct 09 11:40:11 2019 +0200
+++ b/pkg/octree/strtree.go	Wed Oct 09 11:50:33 2019 +0200
@@ -48,6 +48,31 @@
 	s.index[0] = root
 }
 
+func (s *STRTree) BuildWithout(t *Tin, remove map[int32]struct{}) {
+
+	if s.Entries == 0 {
+		s.Entries = STRTreeDefaultEntries
+	}
+
+	s.tin = t
+
+	all := make([]int32, 0, len(t.Triangles)-len(remove))
+
+	for i := range all {
+		idx := int32(i)
+		if _, found := remove[idx]; !found {
+			all = append(all, idx)
+		}
+		all[i] = int32(i)
+	}
+
+	s.index = append(s.index, 0)
+
+	root := s.build(all)
+
+	s.index[0] = root
+}
+
 func (s *STRTree) Clip(p *Polygon) map[int32]struct{} {
 
 	removed := make(map[int32]struct{})