Package org.locationtech.jts.jump.warp

Class Triangulator

  • public class Triangulator
extends Object
    A better name for this class would have been TriangleMapFactory. Given the coordinates of an initial and final triangulation, it will return a map of source Triangle to destination Triangle. Creates a FeatureCollection of triangles covering a given area. Thin triangles are avoided.

    Coordinates are not created, modified, or discarded. Thus, the triangles created will be composed of the Coordinates passed in to the Triangulator. See White, Marvin S., Jr. and Griffin, Patricia. 1985. Piecewise linear rubber-sheet map transformation. "The American Cartographer" 12:2, 123-31.

    • Constructor Detail

      • Triangulator

        public Triangulator()

    • Method Detail

      • triangleMap

        public Map triangleMap​(org.locationtech.jts.geom.Envelope datasetEnvelope,
                       Collection vectorLineStrings,
                       TaskMonitor monitor)
        Splits two regions into Triangles. The two regions are called the "source quadrilateral" and "destination quadrilateral", and are based on the given dataset envelope. The "source quadrilateral" is the dataset envelope expanded 5% along each margin. The "destination quadrilateral" is the source quadrilateral with each vertex shifted according to the vector with the nearest tail. The source quadrilateral is split using the vector tails; the destination quadrilateral is split using the vector tips. In this way, the vectors map the source Triangles to the destination Triangles.
        Parameters:
        datasetEnvelope - the region to triangulate
        vectors - vectors (2-point LineStrings) whose tails and tips split the "source quadrilateral" and "destination quadrilateral" into triangles
        Returns:
        a map of source Triangles to destination Triangles

      • triangleMap

        public Map triangleMap​(org.locationtech.jts.geom.Envelope datasetEnvelope,
                       Collection vectorLineStrings,
                       Collection sourceHints,
                       Collection destinationHints,
                       TaskMonitor monitor)
        Parameters:
        sourceHints - "far-away" Coordinates (even outside the dataset envelope) for which we must ensure that source triangles include.
        destinationHints - "far-away" Coordinates for which we must ensure that destination triangles include

      • getIgnoredVectors

        public Collection getIgnoredVectors()
        Permits the caller to identify which vectors were ignored because they were not 2-point LineStrings

      • vector

        public static boolean vector​(org.locationtech.jts.geom.Geometry g)

      • heightMaximizedTriangles

        protected List heightMaximizedTriangles​(Triangle PQS,
                                        Triangle QRS)
        The intent of this method is to avoid narrow triangles, which create near singularities.
        Parameters:
        PQS - a triangle sharing an edge with QRS; vertex order is irrelevant
        Returns:
        (PQS and QRS) or (PQR, PRS), whichever pair has the largest minimum height

      • triangleContaining

        protected Triangle triangleContaining​(org.locationtech.jts.geom.Coordinate p,
                                      List triangles)
        Returns:
        the triangle containing p, or null if no triangle contains p

      • add

        protected org.locationtech.jts.geom.Coordinate add​(org.locationtech.jts.geom.Coordinate a,
                                                   org.locationtech.jts.geom.LineString vector)
        Returns:
        a + the displacement represented by vector

      • vectorWithNearestTail

        protected org.locationtech.jts.geom.LineString vectorWithNearestTail​(org.locationtech.jts.geom.Coordinate x,
                                                                     List vectors)

      • alternativeTriangles

        protected List alternativeTriangles​(Triangle PQS,
                                    Triangle QRS)
        Parameters:
        PQS - a triangle sharing an edge with QRS; vertex order is irrelevant
        Returns:
        triangles PQR and PRS, or null if PQRS is not convex

      • taggedVectorVertices

        public static List taggedVectorVertices​(boolean tips,
                                        Collection vectors)
        The returned Coordinates will be tagged with the tails if the tips are requested (or the tips, if the tails are requested).
        Parameters:
        tips - true to return the vector tips; otherwise, the tails