Class OffsetCurveSetBuilder


  • public class OffsetCurveSetBuilder
    extends java.lang.Object
    Creates all the raw offset curves for a buffer of a Geometry. Raw curves need to be noded together and polygonized to form the final buffer area.
    Version:
    1.7
    • Field Detail

      • distance

        private double distance
      • curveList

        private java.util.List curveList
    • Constructor Detail

    • Method Detail

      • getCurves

        public java.util.List getCurves()
        Computes the set of raw offset curves for the buffer. Each offset curve has an attached Label indicating its left and right location.
        Returns:
        a Collection of SegmentStrings representing the raw buffer curves
      • addCurve

        private void addCurve​(Coordinate[] coord,
                              int leftLoc,
                              int rightLoc)
        Creates a SegmentString for a coordinate list which is a raw offset curve, and adds it to the list of buffer curves. The SegmentString is tagged with a Label giving the topology of the curve. The curve may be oriented in either direction. If the curve is oriented CW, the locations will be:
        Left: Location.EXTERIOR
        Right: Location.INTERIOR
      • add

        private void add​(Geometry g)
      • addPoint

        private void addPoint​(Point p)
        Add a Point to the graph.
      • addLineString

        private void addLineString​(LineString line)
      • addPolygon

        private void addPolygon​(Polygon p)
      • addPolygonRing

        private void addPolygonRing​(Coordinate[] coord,
                                    double offsetDistance,
                                    int side,
                                    int cwLeftLoc,
                                    int cwRightLoc)
        Adds an offset curve for a polygon ring. The side and left and right topological location arguments assume that the ring is oriented CW. If the ring is in the opposite orientation, the left and right locations must be interchanged and the side flipped.
        Parameters:
        coord - the coordinates of the ring (must not contain repeated points)
        offsetDistance - the distance at which to create the buffer
        side - the side of the ring on which to construct the buffer line
        cwLeftLoc - the location on the L side of the ring (if it is CW)
        cwRightLoc - the location on the R side of the ring (if it is CW)
      • isErodedCompletely

        private boolean isErodedCompletely​(LinearRing ring,
                                           double bufferDistance)
        The ringCoord is assumed to contain no repeated points. It may be degenerate (i.e. contain only 1, 2, or 3 points). In this case it has no area, and hence has a minimum diameter of 0.
        Parameters:
        ringCoord -
        offsetDistance -
        Returns:
      • isTriangleErodedCompletely

        private boolean isTriangleErodedCompletely​(Coordinate[] triangleCoord,
                                                   double bufferDistance)
        Tests whether a triangular ring would be eroded completely by the given buffer distance. This is a precise test. It uses the fact that the inner buffer of a triangle converges on the inCentre of the triangle (the point equidistant from all sides). If the buffer distance is greater than the distance of the inCentre from a side, the triangle will be eroded completely. This test is important, since it removes a problematic case where the buffer distance is slightly larger than the inCentre distance. In this case the triangle buffer curve "inverts" with incorrect topology, producing an incorrect hole in the buffer.
        Parameters:
        triangleCoord -
        bufferDistance -
        Returns: