public bool Init(PolygonUtil.PolyOperation operations, Point2DList polygon1, Point2DList polygon2)
{
Clear();
mOperations = operations;
mOriginalPolygon1 = polygon1;
mOriginalPolygon2 = polygon2;
// Make a copy of the polygons so that we dont modify the originals, and
// force vertices to integer (pixel) values.
mPoly1 = new Point2DList(polygon1);
mPoly1.WindingOrder = Point2DList.WindingOrderType.Default;
mPoly2 = new Point2DList(polygon2);
mPoly2.WindingOrder = Point2DList.WindingOrderType.Default;
// Find intersection points
if (!VerticesIntersect(mPoly1, mPoly2, out mIntersections))
{
// No intersections found - polygons do not overlap.
mError = PolygonUtil.PolyUnionError.NoIntersections;
return false;
}
// make sure edges that intersect more than once are updated to have correct start points
int numIntersections = mIntersections.Count;
for (int i = 0; i < numIntersections; ++i)
{
for (int j = i + 1; j < numIntersections; ++j)
{
if (mIntersections[i].EdgeOne.EdgeStart.Equals(mIntersections[j].EdgeOne.EdgeStart) &&
mIntersections[i].EdgeOne.EdgeEnd.Equals(mIntersections[j].EdgeOne.EdgeEnd))
{
mIntersections[j].EdgeOne.EdgeStart = mIntersections[i].IntersectionPoint;
}
if (mIntersections[i].EdgeTwo.EdgeStart.Equals(mIntersections[j].EdgeTwo.EdgeStart) &&
mIntersections[i].EdgeTwo.EdgeEnd.Equals(mIntersections[j].EdgeTwo.EdgeEnd))
{
mIntersections[j].EdgeTwo.EdgeStart = mIntersections[i].IntersectionPoint;
}
}
}
// Add intersection points to original polygons, ignoring existing points.
foreach (EdgeIntersectInfo intersect in mIntersections)
{
if (!mPoly1.Contains(intersect.IntersectionPoint))
{
mPoly1.Insert(mPoly1.IndexOf(intersect.EdgeOne.EdgeStart) + 1, intersect.IntersectionPoint);
}
if (!mPoly2.Contains(intersect.IntersectionPoint))
{
mPoly2.Insert(mPoly2.IndexOf(intersect.EdgeTwo.EdgeStart) + 1, intersect.IntersectionPoint);
}
}
mPoly1VectorAngles = new List<int>();
for (int i = 0; i < mPoly2.Count; ++i)
{
mPoly1VectorAngles.Add(-1);
}
mPoly2VectorAngles = new List<int>();
for (int i = 0; i < mPoly1.Count; ++i)
{
mPoly2VectorAngles.Add(-1);
}
// Find starting point on the edge of polygon1 that is outside of
// the intersected area to begin polygon trace.
int currentIndex = 0;
do
{
bool bPointInPolygonAngle = PointInPolygonAngle(mPoly1[currentIndex], mPoly2);
mPoly2VectorAngles[currentIndex] = bPointInPolygonAngle ? 1 : 0;
if (bPointInPolygonAngle)
{
mStartingIndex = currentIndex;
break;
}
currentIndex = mPoly1.NextIndex(currentIndex);
} while (currentIndex != 0);
// If we don't find a point on polygon1 thats outside of the
// intersect area, the polygon1 must be inside of polygon2,
// in which case, polygon2 IS the union of the two.
if (mStartingIndex == -1)
{
mError = PolygonUtil.PolyUnionError.Poly1InsidePoly2;
return false;
}
return true;
}
public void Clear()
{
mOperations = PolygonUtil.PolyOperation.None;
mOriginalPolygon1 = null;
mOriginalPolygon2 = null;
mPoly1 = null;
mPoly2 = null;
mIntersections = null;
mStartingIndex = -1;
mError = PolygonUtil.PolyUnionError.None;
mPoly1VectorAngles = null;
mPoly2VectorAngles = null;
mOutput = new Dictionary<uint, Point2DList>();
}
