Force stay into bounds field otherwise we can get infinite derivation which are really annoying..

src/main/java/plugins/adufour/activecontours/Polygon2D.java

@@ -1128,7 +1128,7 @@ public class Polygon2D extends ActiveContour
             // FIXME: it appears to be better to always apply model force but just reducing it (Stephane)
             if ((boundField == null) || boundField.contains(p.x, p.y, 0, 0, 0))
             {
-                if (modelForces[index] != null)
+                if ((modelForces[index] != null) && (nearBounds != null))
                 {
                     // close from border of "bound field" ? --> reduce model forces
                     if ((p.x < nearBounds.getMinX()) || (p.x > nearBounds.getMaxX()))
@@ -1139,11 +1139,16 @@ public class Polygon2D extends ActiveContour
             }
             else
             {
-                // reduce model force
+                // inhibit model force
                 if (modelForces[index] != null)
-                    modelForces[index].scale(0.1);
-                // reduce feedback force
-                feedbackForces[index].scale(0.25);
+                    modelForces[index].scale(0);
+                // inhibit  feedback force
+                feedbackForces[index].scale(0);
+//                // reduce model force
+//                if (modelForces[index] != null)
+//                    modelForces[index].scale(0.1);
+//                // reduce feedback force
+//                feedbackForces[index].scale(0.25);
             }
 
             // set initial model force