diff --git a/src/Lib/Geometry/poly_support.cxx b/src/Lib/Geometry/poly_support.cxx
index 75dcd0e5..139da4fc 100644
--- a/src/Lib/Geometry/poly_support.cxx
+++ b/src/Lib/Geometry/poly_support.cxx
@@ -626,6 +626,20 @@ static void calc_point_inside( TGContourNode *node, TGPolygon &p ) {
     
     if ( contour_num < 0 )
             return;
+    
+    /*
+     * Find a line intersecting the contour and intersect it with the segments
+     * of our children. Sort the intersection points along the line. They then
+     * partition the line in IN/OUT parts. Find the longest segment and take
+     * its midpoint as point inside the contour.
+     */
+    
+    /*
+     * Try to find a line on which none of the contour points lie. For that,
+     * sort all contour points (also those of our direct children) by
+     * y-coordinate, find the two with the largest distance and take their
+     * center y-coordinate.
+     */
     point_list allpoints;
     
     collect_contour_points( node, p, allpoints );
@@ -641,22 +655,25 @@ static void calc_point_inside( TGContourNode *node, TGPolygon &p ) {
     }
     
     sort(allpoints.begin(), allpoints.end(), Point3DOrdering(PY));
-    
-    // cout << "calc_point_inside() " << allpoints.size() << " points ";
-    // copy(allpoints.begin(), allpoints.end(), ostream_iterator<Point3D>(cout, " "));
-    // cout << endl;
-    
+
     point_list::iterator point_it;
     
     point_it=allpoints.begin();
     
-    for (++point_it;point_it!=allpoints.end();++point_it) {
+    double yline; // the y-location of the intersection line
+    
+    while ((++point_it) != allpoints.end()) {
             double diff=point_it->y()-(point_it-1)->y();
-            // cout << "calc_point_inside() diff=" << diff << endl;
             if (diff<=8.0*SG_EPSILON) {
                     continue;
             }
-            double yline=point_it->y()-diff/2.0; // the y-location of the intersection line
+            yline=point_it->y()-diff/2.0;
+            
+            // cout << "calc_point_inside() " << allpoints.size() << " points ";
+            // copy(allpoints.begin(), allpoints.end(), ostream_iterator<Point3D>(cout, " "));
+            // cout << endl;
+        
+            // cout << "calc_point_inside() maxdiff=" << maxdiff << " yline=" << yline << endl;
             
             vector < double > xcuts;