public static CPolyPath ConvertToClipper(PolyLine2d pline, double nIntScale)
{
int N = pline.VertexCount;
CPolyPath clipper_path = new CPolyPath(N);
for (int i = 0; i < N; ++i)
{
Vector2d v = pline[i];
clipper_path.Add(new IntPoint(nIntScale * v.x, nIntScale * v.y));
}
return(clipper_path);
}
public static PolyLine2d ConvertFromClipperPath(CPolyPath clipper_poly, double nIntScale)
{
double scale = 1.0 / (double)nIntScale;
int N = clipper_poly.Count;
PolyLine2d poly = new PolyLine2d();
for (int i = 0; i < N; ++i)
{
IntPoint p = clipper_poly[i];
Vector2d v = new Vector2d((double)p.X * scale, (double)p.Y * scale);
poly.AppendVertex(v);
}
return(poly);
}
/// <summary>
/// remove portions of polyline that are inside set of solids
/// </summary>
public static List <PolyLine2d> ClipAgainstPolygon(IEnumerable <GeneralPolygon2d> solids, PolyLine2d polyline, bool bIntersect = false)
{
double nIntScale = Math.Max(GetIntScale(solids), GetIntScale(polyline.Vertices));
List <PolyLine2d> result = new List <PolyLine2d>();
Clipper clip = new Clipper();
PolyTree tree = new PolyTree();
try {
foreach (GeneralPolygon2d poly in solids)
{
CPolygonList clipper_poly = ConvertToClipper(poly, nIntScale);
clip.AddPaths(clipper_poly, PolyType.ptClip, true);
}
CPolyPath path = ConvertToClipper(polyline, nIntScale);
clip.AddPath(path, PolyType.ptSubject, false);
if (bIntersect)
{
clip.Execute(ClipType.ctIntersection, tree);
}
else
{
clip.Execute(ClipType.ctDifference, tree);
}
for (int ci = 0; ci < tree.ChildCount; ++ci)
{
if (tree.Childs[ci].IsOpen == false)
{
continue;
}
PolyLine2d clippedPath = ConvertFromClipperPath(tree.Childs[ci].Contour, nIntScale);
// clipper just cuts up the polylines, we still have to figure out containment ourselves.
// Currently just checking based on point around middle of polyline...
// [TODO] can we get clipper to not return the inside ones?
Vector2d qp = (clippedPath.VertexCount > 2) ?
clippedPath[clippedPath.VertexCount / 2] : clippedPath.Segment(0).Center;
bool inside = false;
foreach (var poly in solids)
{
if (poly.Contains(qp))
{
inside = true;
break;
}
}
if (inside == bIntersect)
{
result.Add(clippedPath);
}
}
} catch /*(Exception e)*/ {
// [TODO] what to do here?
//System.Diagnostics.Debug.WriteLine("ClipperUtil.ClipAgainstPolygon: Clipper threw exception: " + e.Message);
return(new List <PolyLine2d>());
}
return(result);
}
