anchor.diff:        final int ip = i + 1;
         final int jp = j + 1;
         gb.AddFaces4(1);
  -      gb.AddVertices([
  +      gb.AddVerticesTakeOwnership([
           bands[i][jp * 2],
           bands[ip][jp * 2],
           bands[ip][j * 2],
  
positive.code:   pointsAndTangents.add(pointsAndTangents[1]);
    final int h = segmentsR + 1;
    assert(pointsAndTangents.length == 2 * h);
  
    final List<List<VM.Vector3>> bands =
    TubeHullBands(pointsAndTangents, segmentsT, tubeRadius);
    for (List<VM.Vector3> b in bands) {
  
negative.code: 
    if (computeUVs) {
      gb..EnableAttribute(aTexUV);
      for (int i = segmentsR-1; i >= 0; --i) {
        for (int j = 0; j < segmentsT; ++j) {
          final int ip = i + 1;
          final int jp = j + 1;
          gb.AddAttributesVector2TakeOwnership(aTexUV, [
            VM.Vector2(i / segmentsR, jp / segmentsT),
            VM.Vector2(ip / segmentsR, jp / segmentsT),
            VM.Vector2(ip / segmentsR, j / segmentsT),
  