Hi Dale,

Here is a sample code that I extract from my plugins. Basically if this code execute in Rhino 5, the result will be true, but in Rhino 6, the tolerance has to be non zero in order to get it to return true. It is not a big deal, just want to confirm that the tolerance is important in this situation.

```
point3dList.Add(new Point3d(0, 0, 0));
point3dList.Add(new Point3d(400,0,0));
point3dList.Add(new Point3d(400,400,0));
point3dList.Add(new Point3d(0,400,0));
point3dList.Add(new Point3d(0,0, 0));
PolylineCurve polyLineCurve = new PolylineCurve(point3dList);
RhinoDoc.ActiveDoc.Objects.Add(polyLineCurve);
Point3d pointQ = new Point3d(100, 100, 0);
double yMin = pointQ.Y - (Math.Sqrt(3) * X / 2) / 3 ;
double yMax = pointQ.Y + (Math.Sqrt(3) * X) / 3;
double xMin = pointQ.X - X / 2 ;
double xMax = pointQ.X + X / 2 ;
Line bottom = new Line(xMax, yMin, 0, xMin, yMin, 0);
Line left = new Line(xMin, yMin, 0, pointQ.X, yMax, 0);
Line right = new Line(pointQ.X, yMax, 0, xMax, yMin, 0);
PolyCurve polyCurve = new PolyCurve();
polyCurve.Append(bottom);
polyCurve.Append(left);
polyCurve.Append(right);
RhinoDoc.ActiveDoc.Objects.Add(polyCurve);
if (Curve.PlanarClosedCurveRelationship(polyLineCurve, polyCurve, Plane.WorldXY, 0) == RegionContainment.BInsideA)
{
return true;
}
else
{
return false;
}
```