Package com.google.common.geometry
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:
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Nested Class Summary
Nested Classes -
Field Summary
FieldsModifier and TypeFieldDescription(package private) S2CellId
(package private) byte
(package private) byte
(package private) byte
private static final double
The 4 cells around the equator extend to +/-45 degrees latitude at the midpoints of their top and bottom edges.(package private) double
(package private) double
(package private) double
(package private) double
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptiondouble
Return the approximate area of this cell in steradians.double
Return the average area in steradians of cells at this level.static double
averageArea
(int level) Return the average area in steradians for cells at the given level.private static double
chordDist2
(S2Point uvw, double u, double v) Returns the squared chord distance fromuvw
to positionuv
.clone()
boolean
If this method returns true, the region completely contains the given cell.boolean
Returns true if and only if the given point is contained by the region.private static double
edgeDistance
(double dirIJ, double uv) Given the dot product of a point P with the normal of a u- or v-edge at the given coordinate value, returns the distance from P to that edge.boolean
double
Return the area in steradians of this cell as accurately as possible.int
face()
static S2Cell
fromFace
(int face) Returns the cell corresponding to the given S2 cube face.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 withS2CellId.POS_BITS
bits), and level (range 0..kMaxLevel).getBoundaryDistance
(S2Point target) Returns the distance from the cell boundary to the given point.Returns the bounds of this cell in (u,v)-space.Return a bounding spherical cap.Return the direction vector corresponding to the center in (s,t)-space of the given cell.Return the center of the cell in (u,v) coordinates (seeS2Projections
).getDistance
(S2Cell target) Returns the distance to the given cell.getDistance
(S2Point targetXyz) Returns the distance from the given point to the cell.private double
getDistanceInternal
(S2Point targetXyz, boolean toInterior) Returns the chord distance to targetXyz, with interior distance 0 iff toInterior is true.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.getEdge
(int k) AsgetEdgeRaw(int)
, except the point is normalized to unit length.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).getMaxDistance
(S2Cell target) Returns the maximum distance from the cell, including interior, to the given target cell.getMaxDistance
(S2Point target) Returns the maximum distance from the cell (including its interior) to the given point.getMaxDistance
(S2Point a, S2Point b) Returns the maximum distance from the cell (including its interior) to the given edge AB.private S2Point
getPoint
(int i, int j) Return a bounding latitude-longitude rectangle.int
AsS2CellId.getSizeIJ(int)
, using the level of this cell.getVertex
(int k) AsgetVertexRaw(int)
, except the point is normalized to unit length.getVertexRaw
(int k) Returns the kth vertex of the cell (k = 0,1,2,3).int
hashCode()
id()
private void
boolean
isLeaf()
Returns true if this cell is a leaf-cell, i.e.byte
level()
boolean
mayIntersect
(S2Cell cell) If this method returns false, the region does not intersect the given cell.byte
(package private) void
setBoundUV
(R2Rect bound) Sets the bounds of this cell in (u,v)-space into 'bound'.boolean
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.toString()
private boolean
uEdgeIsClosest
(S2Point p, boolean vEnd) Given a pointp
and either the lower or upper edge of theS2Cell
(specified by settingvEnd
to false or true respectively), returns true ifp
is closer to the interior of that edge than it is to either endpoint.private boolean
vEdgeIsClosest
(S2Point p, boolean uEnd) Given a pointp
and either the left or right edge of theS2Cell
(specified by settinguEnd
to false or true respectively), returns true ifp
is closer to the interior of that edge than it is to either endpoint.private double
vertexChordDist2
(S2Point uvw, S2Cell.DoubleBinaryOperator reducer)
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Field Details
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face
byte face -
level
byte level -
orientation
byte orientation -
cellId
S2CellId cellId -
uMin
double uMin -
uMax
double uMax -
vMin
double vMin -
vMax
double vMax -
POLE_MIN_LAT
private static final double POLE_MIN_LATThe 4 cells around the equator extend to +/-45 degrees latitude at the midpoints of their top and bottom edges. The two cells covering the poles extend down to +/-35.26 degrees at their vertices. The maximum error in this calculation is 0.5 * DBL_EPSILON.
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Constructor Details
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S2Cell
S2Cell()Default constructor used only internally. -
S2Cell
An S2Cell always corresponds to a particular S2CellId. The other constructors are just convenience methods. -
S2Cell
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S2Cell
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Method Details
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fromFace
Returns the cell corresponding to the given S2 cube face. -
fromFacePosLevel
Returns a cell given its face (range 0..5), Hilbert curve position within that face (an unsigned integer withS2CellId.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
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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
AsgetVertexRaw(int)
, except the point is normalized to unit length. -
getVertexRaw
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
AsgetEdgeRaw(int)
, except the point is normalized to unit length. -
getEdgeRaw
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()AsS2CellId.getSizeIJ(int)
, using the level of this cell. -
subdivide
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.
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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
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getBoundUV
Returns the bounds of this cell in (u,v)-space. -
setBoundUV
Sets the bounds of this cell in (u,v)-space into 'bound'.Package private to avoid leaking object mutation outside the api.
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getCenterUV
Return the center of the cell in (u,v) coordinates (seeS2Projections
). 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
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getCapBound
Description copied from interface:S2Region
Return a bounding spherical cap.- Specified by:
getCapBound
in interfaceS2Region
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getRectBound
Description copied from interface:S2Region
Return a bounding latitude-longitude rectangle.- Specified by:
getRectBound
in interfaceS2Region
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mayIntersect
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 interfaceS2Region
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contains
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. -
contains
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. -
vertexChordDist2
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chordDist2
Returns the squared chord distance fromuvw
to positionuv
. -
uEdgeIsClosest
Given a pointp
and either the lower or upper edge of theS2Cell
(specified by settingvEnd
to false or true respectively), returns true ifp
is closer to the interior of that edge than it is to either endpoint. -
vEdgeIsClosest
Given a pointp
and either the left or right edge of theS2Cell
(specified by settinguEnd
to false or true respectively), returns true ifp
is closer to the interior of that edge than it is to either endpoint. -
edgeDistance
private static double edgeDistance(double dirIJ, double uv) Given the dot product of a point P with the normal of a u- or v-edge at the given coordinate value, returns the distance from P to that edge. -
getDistance
Returns the distance from the given point to the cell. Returns zero if the point is inside the cell. -
getDistance
Returns the distance to the given cell. Returns zero if one cell contains the other. -
getDistanceInternal
Returns the chord distance to targetXyz, with interior distance 0 iff toInterior is true. -
getMaxDistance
Returns the maximum distance from the cell (including its interior) to the given point. -
getMaxDistance
Returns the maximum distance from the cell (including its interior) to the given edge AB. -
getMaxDistance
Returns the maximum distance from the cell, including interior, to the given target cell. -
getDistanceToEdge
Returns the minimum distance from the cell to the given edge AB, or zero if the edge intersects the cell interior. -
getBoundaryDistance
Returns the distance from the cell boundary to the given point. -
init
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getPoint
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toString
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hashCode
public int hashCode() -
equals
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