/// <summary>
/// Get two vectors, which indicate some edge direction which contain given point,
/// set the given point as the start point, the other end point of the edge as end
/// </summary>
/// <param name="edges">polygon</param>
/// <param name="point">a point of the polygon</param>
/// <returns>two vectors indicate edge direction</returns>
public static IList <Vector3d> GetRelatedVectors(IList <Line> edges, Vector3d point)
{
// Initialize the return vector list.
List <Vector3d> vectors = new List <Vector3d>();
// Get all the edge which contain this point.
// And get the vector from this point to another point
foreach (Line line in edges)
{
if (point.IsAlmostEqualTo(line.StartPoint))
{
Vector3d vector = PolylineOffsetUtil.SubXYZ(line.EndPoint, line.StartPoint);
vectors.Add(vector);
}
if (point.IsAlmostEqualTo(line.EndPoint))
{
Vector3d vector = PolylineOffsetUtil.SubXYZ(line.StartPoint, line.EndPoint);
vectors.Add(vector);
}
}
// only two vector(direction) should be found
if (2 != vectors.Count)
{
throw new Exception("a point on polygon should have only two direction.");
}
return(vectors);
}
public static Dictionary <Vector2d, PointRelativePos> OffsetPoints(IList <Vector2d> oriPoints, double offset)
{
if (PolylineOffsetUtil.IsAlmostZero(offset))
{
Dictionary <Vector2d, PointRelativePos> map = OffsetPoints(oriPoints, 1.0);
Dictionary <Vector2d, PointRelativePos> result = new Dictionary <Vector2d, PointRelativePos>();
int i = 0;
foreach (KeyValuePair <Vector2d, PointRelativePos> keyValue in map)
{
result.Add(oriPoints[i++], keyValue.Value);
}
return(result);
}
// Initialize the offset point list.
Dictionary <Vector2d, PointRelativePos> points = new Dictionary <Vector2d, PointRelativePos>();
IList <Vector3d> oriPointsVector3d = PolylineOffsetUtil.Inflatten(oriPoints);
IList <Line> lineList = PolylineOffsetUtil.ChangeProfilePointListToLine(oriPointsVector3d);
// Get all points of the swept profile, and offset it in two related direction
foreach (Vector3d point in oriPointsVector3d)
{
// Get two related directions
IList <Vector3d> directions = GetRelatedVectors(lineList, point);
Vector3d firstDir = directions[0];
Vector3d secondDir = directions[1];
// offset the point in two direction
Vector3d movedPoint = PolylineOffsetUtil.OffsetPoint(point, firstDir, offset);
movedPoint = PolylineOffsetUtil.OffsetPoint(movedPoint, secondDir, offset);
PointRelativePos posFlag = PointRelativePos.Inner;
Vector2d pointVector2d = PolylineOffsetUtil.Flatten(movedPoint);
if (offset > 0)
{
if (!(PolygonContains(oriPoints, pointVector2d)))
{
movedPoint = PolylineOffsetUtil.OffsetPoint(point, firstDir, offset * -1.0);
movedPoint = PolylineOffsetUtil.OffsetPoint(movedPoint, secondDir, offset * -1.0);
posFlag = PointRelativePos.Outer;
}
}
else
{
if (PolygonContains(oriPoints, pointVector2d))
{
movedPoint = PolylineOffsetUtil.OffsetPoint(point, firstDir, offset * -1.0);
movedPoint = PolylineOffsetUtil.OffsetPoint(movedPoint, secondDir, offset * -1.0);
posFlag = PointRelativePos.Outer;
}
}
// add the offset point into the array
points.Add(new Vector2d(movedPoint.x, movedPoint.y), posFlag);
}
return(points);
}