--- a/pkg/octree/vertex.go	Thu Sep 27 10:57:39 2018 +0200
+++ b/pkg/octree/vertex.go	Thu Sep 27 11:40:02 2018 +0200
@@ -237,17 +237,27 @@
 
 	out := make(MultiLineStringZ, 0, len(positions))
 
+	var ignored int
+
 	for i := range positions {
 		curr := positions[i].line
 		if l := len(out); l > 0 {
-			if last := out[l-1]; last[len(last)-1].EpsEquals(curr[0]) {
+			last := out[l-1]
+
+			if last[len(last)-1].EpsEquals(curr[0]) {
 				out[l-1] = append(last[:len(last)-1], curr...)
 				continue
 			}
+			if position(last[len(last)-1]) > position(curr[0]) {
+				ignored++
+				continue
+			}
 		}
 		out = append(out, curr)
 	}
 
+	log.Printf("ignored parts: %d\n", ignored)
+
 	return out
 }
 
@@ -450,6 +460,10 @@
 
 	var out LineStringZ
 
+	defer func() {
+		log.Printf("length out: %d\n", len(out))
+	}()
+
 edges:
 	for i := 0; i < 3 && len(out) < 2; i++ {
 		j := (i + 1) % 3
@@ -461,7 +475,7 @@
 		o1 := onPlane(s1)
 		o2 := onPlane(s2)
 
-		log.Printf("s1, s2: %t %t\n", o1, o2)
+		log.Printf("s1, s2: %t %t (%f %f)\n", o1, o2, s1, s2)
 
 		switch {
 		case o1 && o2:
@@ -527,8 +541,6 @@
 
 			log.Println("Intersection -----------------------------")
 			t1 := relative(t[i], t[j])(x, y)
-			log.Printf("rel p1: %f\n", relative(t[i], t[j])(t[i].X, t[i].Y))
-			log.Printf("rel p2: %f\n", relative(t[i], t[j])(t[j].X, t[j].Y))
 			log.Printf("relative pos: %f\n", t1)
 			if !inRange(t1) {
 				continue edges
@@ -613,8 +625,6 @@
 		}
 	}
 
-	log.Printf("length out: %d\n", len(out))
-
 	// supress single point touches.
 	if len(out) == 1 {
 		out = out[:0]