Offset curve line Vectrosity

I'm trying to draw lines with offset to main line like on attachment.

I have problems with my code. It generating crosses on the lines if curve is small. (attachment)

Maybe someone can help me with this code or know any good algorithm to generate curved lines with offset

 // LEFT SIDE OF MAIN LINE
         int numberOfLines = 10;
         float offset = 10f;
         lastLinePoints = outerPoints; // outerPoint = Points from Main Line
         for(int i = 0; i < numberOfLines; i++)
         {
             List<Vector3> tempPoints = new List<Vector3> ();
             for (int k = 0; k < lastLinePoints.Count; k++) {
                 if (k + 1 < lastLinePoints.Count) {
                     Vector3 direction = lastLinePoints [k + 1] - lastLinePoints [k];
                     // up direction:
                     Vector3 up = new Vector3(0.0f, 1.0f, 0.0f);
                     // find right vector:
                     Vector3 right =  Vector3.Cross(direction.normalized, up.normalized);
                     Vector3 newPoint = lastLinePoints [k] + (right * offset);
                     tempPoints.Add (newPoint);
                 }
 
 
             }
             VectorLine lineTemp = new VectorLine ("lineCurved", tempPoints, 120f / _camera2DObject.GetComponent<Camera> ().orthographicSize, LineType.Continuous);
             lineTemp.Draw3D ();
             lastLinePoints = tempPoints;
 
         }