Index: trunk/doc/developer/polybool2/algo.txt
===================================================================
--- trunk/doc/developer/polybool2/algo.txt	(revision 36920)
+++ trunk/doc/developer/polybool2/algo.txt	(revision 36921)
@@ -47,11 +47,10 @@
 		- canon A:       out = inA
 
 4. figure which curves to keep: for each curve:
-	- if the curve has two adjacent faces, keep the curve the ->out of those
-	  two faces are not equal
-	- if the curve has only one adjacent face, keep the curve if the
-	  face's ->out is 1
-	Discarded curves are removed and freed.
+	- if the curve has two adjacent faces, mark the curve visited if the
+	  ->out of those two faces are equal
+	- if the curve has only one adjacent face, mark the curve visited if
+	  face's ->out is negaive (not filled)
 
 5. gather curves into output faces:
 	5.1. take a the leftmost/topmost curve and put it on an output curve list