/// <summary>Returns a polygon formed by intersecting an arbitrary polygon with a convex polygon.</summary>
public static PolygonD PolygonWithConvexPolygon(PolygonD mainPoly, PolygonD clipPoly)
{
if (mainPoly.Vertices.Count <= 2 || clipPoly.Vertices.Count <= 2)
{
throw new InvalidOperationException("One of the polygons has 2 vertices or fewer.");
}
var result = new List <PointD>();
var resultVertices = mainPoly.Vertices.ToList();
foreach (var clipEdge in clipPoly.ToEdges())
{
var newVertices = new List <PointD>();
var vertexStart = resultVertices[resultVertices.Count - 1];
foreach (var vertexEnd in resultVertices)
{
if (clipEdge.CrossZ(vertexStart) > 0)
{
if (clipEdge.CrossZ(vertexEnd) > 0)
{
newVertices.Add(vertexEnd);
}
else
{
newVertices.Add(Intersect.LineWithLine(clipEdge, new EdgeD(vertexStart, vertexEnd)));
}
}
else
{
if (clipEdge.CrossZ(vertexEnd) > 0)
{
newVertices.Add(Intersect.LineWithLine(clipEdge, new EdgeD(vertexStart, vertexEnd)));
newVertices.Add(vertexEnd);
}
}
vertexStart = vertexEnd;
}
resultVertices = newVertices;
}
return(new PolygonD(resultVertices));
}
/// <summary>Returns a polygon formed by intersecting an arbitrary polygon with a convex polygon.</summary>
public static PolygonD PolygonWithConvexPolygon(PolygonD mainPoly, PolygonD clipPoly)
{
if (mainPoly.Vertices.Count <= 2 || clipPoly.Vertices.Count <= 2)
throw new InvalidOperationException("One of the polygons has 2 vertices or fewer.");
var result = new List<PointD>();
var resultVertices = mainPoly.Vertices.ToList();
foreach (var clipEdge in clipPoly.ToEdges())
{
var newVertices = new List<PointD>();
var vertexStart = resultVertices[resultVertices.Count - 1];
foreach (var vertexEnd in resultVertices)
{
if (clipEdge.CrossZ(vertexStart) > 0)
{
if (clipEdge.CrossZ(vertexEnd) > 0)
newVertices.Add(vertexEnd);
else
newVertices.Add(Intersect.LineWithLine(clipEdge, new EdgeD(vertexStart, vertexEnd)));
}
else
{
if (clipEdge.CrossZ(vertexEnd) > 0)
{
newVertices.Add(Intersect.LineWithLine(clipEdge, new EdgeD(vertexStart, vertexEnd)));
newVertices.Add(vertexEnd);
}
}
vertexStart = vertexEnd;
}
resultVertices = newVertices;
}
return new PolygonD(resultVertices);
}