Class S2Cell

java.lang.Object
com.google.common.geometry.S2Cell
All Implemented Interfaces:
S2Region, Serializable
@GwtCompatible(serializable=true) public final class S2Cell extends Object implements S2Region, Serializable
An S2Cell is an S2Region object that represents a cell. Unlike S2CellIds, it supports efficient containment and intersection tests. However, it is also a more expensive representation.
See Also:

  • Constructor Details

    • S2Cell

      public S2Cell(S2CellId id)
      An S2Cell always corresponds to a particular S2CellId. The other constructors are just convenience methods.

    • S2Cell

      public S2Cell(S2Point p)

    • S2Cell

      public S2Cell(S2LatLng ll)

  • Method Details

    • fromFace

      public static S2Cell fromFace(int face)
      Returns the cell corresponding to the given S2 cube face.

    • fromFacePosLevel

      public static S2Cell fromFacePosLevel(int face, long pos, int level)
      Returns a cell given its face (range 0..5), Hilbert curve position within that face (an unsigned integer with S2CellId.POS_BITS bits), and level (range 0..kMaxLevel). The given position will be modified to correspond to the Hilbert curve position at the center of the returned cell. This is a static function rather than a constructor in order to indicate what the arguments represent.

    • id

      public S2CellId id()

    • face

      public int face()

    • level

      public byte level()

    • orientation

      public byte orientation()

    • isLeaf

      public boolean isLeaf()
      Returns true if this cell is a leaf-cell, i.e. it has no children.

    • getVertex

      public S2Point getVertex(int k)
      As getVertexRaw(int), except the point is normalized to unit length.

    • getVertexRaw

      public S2Point getVertexRaw(int k)
      Returns the kth vertex of the cell (k = 0,1,2,3). Vertices are returned in CCW order (lower left, lower right, upper right, upper left in the UV plane). The points are not necessarily unit length.

    • getEdge

      public S2Point getEdge(int k)
      As getEdgeRaw(int), except the point is normalized to unit length.

    • getEdgeRaw

      public S2Point getEdgeRaw(int k)
      Returns the inward-facing normal of the great circle passing through the edge from vertex k to vertex k+1 (mod 4). The normals returned by getEdgeRaw are not necessarily unit length.

    • getSizeIJ

      public int getSizeIJ()
      As S2CellId.getSizeIJ(int), using the level of this cell.

    • subdivide

      public boolean subdivide(S2Cell[] children)
      Returns true if this is not a leaf cell, in which case the array, which must contain at least four non-null cells in indices 0..3, will be set to the four children of this cell in traversal order. Otherwise, if this is a leaf cell, false is returned without touching the array.

      This method is equivalent to the following: 

      for (pos=0, id=childBegin(); !id.equals(childEnd()); id = id.next(), ++pos) {
  children[i].init(id);
}

      except that it is more than two times faster.

    • getCenter

      public S2Point getCenter()
      Return the direction vector corresponding to the center in (s,t)-space of the given cell. This is the point at which the cell is divided into four subcells; it is not necessarily the centroid of the cell in (u,v)-space or (x,y,z)-space. The point returned by GetCenterRaw is not necessarily unit length.

    • getCenterRaw

      public S2Point getCenterRaw()

    • getBoundUV

      public R2Rect getBoundUV()
      Returns the bounds of this cell in (u,v)-space.

    • getCenterUV

      public R2Vector getCenterUV()
      Return the center of the cell in (u,v) coordinates (see S2Projections). Note that the center of the cell is defined as the point at which it is recursively subdivided into four children; in general, it is not at the midpoint of the (u,v) rectangle covered by the cell

    • averageArea

      public static double averageArea(int level)
      Return the average area in steradians for cells at the given level.

    • averageArea

      public double averageArea()
      Return the average area in steradians of cells at this level. This is accurate to within a factor of 1.7 (for S2_QUADRATIC_PROJECTION) and is extremely cheap to compute.

    • approxArea

      public double approxArea()
      Return the approximate area of this cell in steradians. This method is accurate to within 3% percent for all cell sizes and accurate to within 0.1% for cells at level 5 or higher (i.e. 300km square or smaller). It is moderately cheap to compute.

    • exactArea

      public double exactArea()
      Return the area in steradians of this cell as accurately as possible. This method is more expensive but it is accurate to 6 digits of precision even for leaf cells (whose area is approximately 1e-18).

    • clone

      public S2Region clone()
      Overrides:
      clone in class Object

    • getCapBound

      public S2Cap getCapBound()
      Description copied from interface: S2Region
      Return a bounding spherical cap.
      Specified by:
      getCapBound in interface S2Region

    • getRectBound

      public S2LatLngRect getRectBound()
      Description copied from interface: S2Region
      Return a bounding latitude-longitude rectangle.
      Specified by:
      getRectBound in interface S2Region

    • mayIntersect

      public boolean mayIntersect(S2Cell cell)
      Description copied from interface: S2Region
      If this method returns false, the region does not intersect the given cell. Otherwise, either region intersects the cell, or the intersection relationship could not be determined.
      Specified by:
      mayIntersect in interface S2Region

    • contains

      public boolean contains(S2Point p)
      Description copied from interface: S2Region
      Returns true if and only if the given point is contained by the region. p is generally required to be unit length, although some subtypes may relax this restriction.
      Specified by:
      contains in interface S2Region

    • contains

      public boolean contains(S2Cell cell)
      Description copied from interface: S2Region
      If this method returns true, the region completely contains the given cell. Otherwise, either the region does not contain the cell or the containment relationship could not be determined.
      Specified by:
      contains in interface S2Region

    • getDistance

      public S1ChordAngle getDistance(S2Point targetXyz)
      Returns the distance from the given point to the cell. Returns zero if the point is inside the cell.

    • getDistance

      public S1ChordAngle getDistance(S2Cell target)
      Returns the distance to the given cell. Returns zero if one cell contains the other.

    • getMaxDistance

      public S1ChordAngle getMaxDistance(S2Point target)
      Returns the maximum distance from the cell (including its interior) to the given point.

    • getMaxDistance

      public S1ChordAngle getMaxDistance(S2Point a, S2Point b)
      Returns the maximum distance from the cell (including its interior) to the given edge AB.

    • getMaxDistance

      public S1ChordAngle getMaxDistance(S2Cell target)
      Returns the maximum distance from the cell, including interior, to the given target cell.

    • getDistanceToEdge

      public S1ChordAngle getDistanceToEdge(S2Point a, S2Point b)
      Returns the minimum distance from the cell to the given edge AB, or zero if the edge intersects the cell interior.

    • getBoundaryDistance

      public S1ChordAngle getBoundaryDistance(S2Point target)
      Returns the distance from the cell boundary to the given point.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object that)
      Overrides:
      equals in class Object