Package gov.nasa.worldwind.util

Class BitSetQuadTreeFilter.FindIntersectingBitsOp

  • Enclosing class:
    BitSetQuadTreeFilter
    public static class BitSetQuadTreeFilter.FindIntersectingBitsOp
extends BitSetQuadTreeFilter
    A quadtree filter that determines the bit positions of cells associated with items and intersecting a specified region. Typically used to traverse the bit-set index of a populated quadtree to determine potentially visible items.

    This class requires a previously populated filter and determines which of its cells intersect a specified sector.

    • Field Detail

      • intersectingBits

        protected java.util.List<java.lang.Integer> intersectingBits

    • Constructor Detail

      • FindIntersectingBitsOp

        public FindIntersectingBitsOp​(BitSetQuadTreeFilter filter)
        Constructs a filter instance.
        Parameters:
        filter - a filter identifying significant cells in a quadtree, typically produced by applying a filter that identifies quadtree cells associated with items.
        Throws:
        java.lang.NullPointerException - if filter is null.
        java.lang.IllegalArgumentException - if filter is invalid.

    • Method Detail

      • getOnBits

        public java.util.List<java.lang.Integer> getOnBits​(java.util.List<double[]> topRegions,
                                                   Sector testSector,
                                                   java.util.List<java.lang.Integer> outIds)
        Returns the bit positions of significant cells that intersect a specified sector. Significant cells are those identified by the filter specified to the constructor.
        Parameters:
        topRegions - the zeroth-level regions of a quadtree.
        testSector - the sector of interest. Significant cells that intersect this sector are returned.
        outIds - a list in which to place the bit positions of intersecting significant cells. May be null, in which case a new list is created. In either case the list is the return value of the method.
        Returns:
        the bit positions of intersecting significant cells. This is the list specified as the non-null outIds argument, or a new list if that argument is null.
        Throws:
        java.lang.IllegalArgumentException - if either topRegions or testSector is null.

      • getOnBits

        public java.util.List<java.lang.Integer> getOnBits​(java.util.List<double[]> topRegions,
                                                   double[] testRegion,
                                                   java.util.List<java.lang.Integer> outIds)
        Returns the bit positions of significant cells that intersect a specified sector. Significant cells are those identified by the filter specified to the constructor.
        Parameters:
        topRegions - the zeroth-level regions of a quadtree.
        testRegion - the sector of interest, specified as a four-element array containing minimum latitude, maximum latitude, minimum longitude and maximum longitude, in that order. Significant cells that intersect this sector are returned.
        outIds - a list in which to place the bit positions of intersecting significant cells. May be null, in which case a new list is created. In either case the list is the return value of the method.
        Returns:
        the bit positions of intersecting significant cells. This is the list specified as the non-null outIds argument, or a new list if that argument is null.
        Throws:
        java.lang.IllegalArgumentException - if either topRegions or testSector is null.

      • doOperation

        protected boolean doOperation​(int level,
                              int position,
                              double[] cellRegion,
                              double[] testSector)
        Assembles the output bit-list during traversal. Implements the abstract method BitSetQuadTreeFilter.doOperation(int, int, double[], double[]). See the description of that method for further detail.
        Specified by:
        doOperation in class BitSetQuadTreeFilter
        Parameters:
        level - the quadtree level currently being traversed.
        position - the position of the cell in its parent cell, either 0, 1, 2, or 3. Cell positions starts with 0 at the southwest corner of the parent cell and increment counter-clockwise: cell 1 is SE, cell 2 is NE and cell 3 is NW.
        cellRegion - an array specifying the coordinates of the cell's region. The first two entries are the minimum and maximum values on the Y axis (typically latitude). The last two entries are the minimum and maximum values on the X axis, (typically longitude).
        testSector - an array specifying the region or location of the intersecting item. If the array's length is 2 then it represents a location in [latitude, longitude]. If its length is 4 it represents a region, with the same layout as the nodeRegion argument.
        Returns:
        true if traversal should continue to the cell's descendants, false if traversal should not continue to the cell's descendants.