private double ClippedArea()
{
if (this.Voids == null || this.Voids.Count == 0)
{
return(this.Perimeter.Area());
}
var clipper = new ClipperLib.Clipper();
var normal = Perimeter.Normal();
if (normal.IsAlmostEqualTo(Vector3.ZAxis))
{
clipper.AddPath(Perimeter.ToClipperPath(), ClipperLib.PolyType.ptSubject, true);
clipper.AddPaths(this.Voids.Select(p => p.ToClipperPath()).ToList(), ClipperLib.PolyType.ptClip, true);
}
else
{
var transform = new Transform(Perimeter.Start, normal);
transform.Invert();
var perimeter = Perimeter.TransformedPolygon(transform);
clipper.AddPath(perimeter.ToClipperPath(), ClipperLib.PolyType.ptSubject, true);
clipper.AddPaths(this.Voids.Select(p => p.TransformedPolygon(transform).ToClipperPath()).ToList(), ClipperLib.PolyType.ptClip, true);
}
var solution = new List <List <ClipperLib.IntPoint> >();
clipper.Execute(ClipperLib.ClipType.ctDifference, solution, ClipperLib.PolyFillType.pftEvenOdd);
return(solution.Sum(s => ClipperLib.Clipper.Area(s)) / Math.Pow(1.0 / Vector3.EPSILON, 2));
}