--- a/pkg/octree/vertex.go	Tue Oct 09 00:37:23 2018 +0200
+++ b/pkg/octree/vertex.go	Tue Oct 09 13:30:45 2018 +0200
@@ -425,28 +425,23 @@
 	for head, lines := range heads {
 		for i, line := range *lines {
 			tail := quant(line[len(line)-1])
-			if hs := heads[tail]; hs != nil {
+			for hs := heads[tail]; hs != nil && len(*hs) > 0; hs = heads[tail] {
 				l := len(*hs)
 				last := (*hs)[l-1]
-				if l == 1 {
-					delete(heads, tail)
-				} else {
-					(*hs)[l-1] = nil
-					*hs = (*hs)[:l-1]
-				}
+				(*hs)[l-1] = nil
+				*hs = (*hs)[:l-1]
 				line = line.Join(last)
 
-				if head == quant(line[len(line)-1]) { // its a ring
+				if tail = quant(line[len(line)-1]); head == tail { // its a ring
 					out = append(out, line)
 					// remove from current lines
 					copy((*lines)[i:], (*lines)[i+1:])
 					(*lines)[len(*lines)-1] = nil
 					*lines = (*lines)[:len(*lines)-1]
-				} else {
-					// overwrite in current lines
-					(*lines)[i] = line
+					goto again
 				}
-				goto again
+				// overwrite in current lines
+				(*lines)[i] = line
 			}
 		}
 	}