diff --git a/jni/triangle/TriangleJni.c b/jni/triangle/TriangleJni.c
index 77fadda6..7d550874 100644
--- a/jni/triangle/TriangleJni.c
+++ b/jni/triangle/TriangleJni.c
@@ -23,6 +23,26 @@ int pnpoly(int nvert, float *vert, float testx, float testy)
    }
    return c;
 }
+
+int compare_dups(const void *a, const void *b) {
+   int da = *((const long*) a);
+   int db = *((const long*) b);
+   return (da > db) - (da < db);
+}
+
+void shiftSegment(TriangleIO *in, int *seg, int pos) {
+   int size = (in->numberofsegments - pos - 1) * sizeof(int) * 2;
+   printf("shift %d - %d %d\n", size, in->numberofsegments, pos);
+   if (size > 0)
+      memmove(seg, seg + 2, size);
+
+   in->numberofsegments -= 1;
+}
+struct {
+   int p1;
+   int p2;
+} segment;
+
 #endif
 
 static void printPoly(TriangleIO *in) {
@@ -188,7 +208,7 @@ jint Java_org_oscim_renderer_sublayers_ExtrusionLayer_triangulate(JNIEnv *env, j
       }
       printPoly(&in);
 
-      // shift segment indices while removing duplicate points
+      // replace duplicate positions with first occurence
       for (int i = 0; i < dups; i++) {
          // position of the duplicate vertex
          int pos = skip_list[i * 2] - i;
@@ -197,8 +217,10 @@ jint Java_org_oscim_renderer_sublayers_ExtrusionLayer_triangulate(JNIEnv *env, j
 
          seg = in.segmentlist;
          for (int j = 0; j < in.numberofsegments * 2; j++, seg++) {
-            if (*seg == pos)
+            if (*seg == pos) {
+               printf("%d: %d <- %d", j, pos, replacement);
                *seg = replacement;
+            }
          }
       }
    }
diff --git a/jni/triangle/triangle.c b/jni/triangle/triangle.c
index 88575a3e..79636f01 100644
--- a/jni/triangle/triangle.c
+++ b/jni/triangle/triangle.c
@@ -310,7 +310,7 @@ void trifree(VOID *memptr) {
 int error_set = 0;
 void internalerror() {
    error_set = 1;
-
+   printf("Triangle is going to quit its job now\n");
    //printf("  Please report this bug to jrs@cs.berkeley.edu\n");
    ///printf("  Include the message above, your input data set, and the exact\n");
    //printf("    command line you used to run Triangle.\n");
@@ -6670,6 +6670,21 @@ void transfernodes(struct mesh *m, struct behavior *b, REAL *pointlist, REAL *po
          /* If no markers are specified, they default to zero. */
          setvertexmark(vertexloop, 0);
       }
+
+      // ----------------------------------------------
+      for (j = (i - 1) * 2; j >= 0; j -= 2){
+         if (x == pointlist[j] && y == pointlist[j+1]){
+            printf("skip duplicate %d\n", j >> 1);
+            setvertextype(vertexloop, UNDEADVERTEX);
+            vertexloop[0] = 0xffffffff;
+            vertexloop[1] = 0xffffffff;
+            break;
+         }
+      }
+      if (j >= 0)
+         continue;
+      // ----------------------------------------------
+
       setvertextype(vertexloop, INPUTVERTEX);
       /* Determine the smallest and largest x and y coordinates. */
       if (i == 0) {