org.hipparchus.geometry.spherical.twod

## Class S2Point

• All Implemented Interfaces:
Serializable, Point<Sphere2D>

public class S2Point
extends Object
implements Point<Sphere2D>
This class represents a point on the 2-sphere.

We use the mathematical convention to use the azimuthal angle $$\theta$$ in the x-y plane as the first coordinate, and the polar angle $$\varphi$$ as the second coordinate (see Spherical Coordinates in MathWorld).

Instances of this class are guaranteed to be immutable.

Serialized Form
• ### Field Summary

Fields
Modifier and Type Field and Description
static S2Point MINUS_I
-I (coordinates: $$\theta = \pi, \varphi = \pi/2$$).
static S2Point MINUS_J
-J (coordinates: $$\theta = 3\pi/2, \varphi = \pi/2$$).
static S2Point MINUS_K
-K (coordinates: $$\theta = any angle, \varphi = \pi$$).
static S2Point NaN
A vector with all coordinates set to NaN.
static S2Point PLUS_I
+I (coordinates: $$\theta = 0, \varphi = \pi/2$$).
static S2Point PLUS_J
+J (coordinates: $$\theta = \pi/2, \varphi = \pi/2$$)).
static S2Point PLUS_K
+K (coordinates: $$\theta = any angle, \varphi = 0$$).
• ### Constructor Summary

Constructors
Constructor and Description
S2Point(double theta, double phi)
Simple constructor.
S2Point(Vector3D vector)
Simple constructor.
• ### Method Summary

All Methods
Modifier and Type Method and Description
double distance(Point<Sphere2D> point)
Compute the distance between the instance and another point.
static double distance(S2Point p1, S2Point p2)
Compute the distance (angular separation) between two points.
boolean equals(Object other)
Test for the equality of two points on the 2-sphere.
boolean equalsIeee754(Object other)
Test for the equality of two points on the 2-sphere.
double getPhi()
Get the polar angle $$\varphi$$.
Space getSpace()
Get the space to which the point belongs.
double getTheta()
Get the azimuthal angle $$\theta$$ in the x-y plane.
Vector3D getVector()
Get the corresponding normalized vector in the 3D euclidean space.
int hashCode()
Get a hashCode for the point.
boolean isNaN()
Returns true if any coordinate of this point is NaN; false otherwise
S2Point negate()
Get the opposite of the instance.
String toString()
• ### Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait
• ### Field Detail

• #### PLUS_I

public static final S2Point PLUS_I
+I (coordinates: $$\theta = 0, \varphi = \pi/2$$).
• #### PLUS_J

public static final S2Point PLUS_J
+J (coordinates: $$\theta = \pi/2, \varphi = \pi/2$$)).
• #### PLUS_K

public static final S2Point PLUS_K
+K (coordinates: $$\theta = any angle, \varphi = 0$$).
• #### MINUS_I

public static final S2Point MINUS_I
-I (coordinates: $$\theta = \pi, \varphi = \pi/2$$).
• #### MINUS_J

public static final S2Point MINUS_J
-J (coordinates: $$\theta = 3\pi/2, \varphi = \pi/2$$).
• #### MINUS_K

public static final S2Point MINUS_K
-K (coordinates: $$\theta = any angle, \varphi = \pi$$).
• #### NaN

public static final S2Point NaN
A vector with all coordinates set to NaN.
• ### Constructor Detail

• #### S2Point

public S2Point(double theta,
double phi)
throws MathIllegalArgumentException
Simple constructor. Build a vector from its spherical coordinates
Parameters:
theta - azimuthal angle $$\theta$$ in the x-y plane
phi - polar angle $$\varphi$$
Throws:
MathIllegalArgumentException - if $$\varphi$$ is not in the [$$0; \pi$$] range
getTheta(), getPhi()
• #### S2Point

public S2Point(Vector3D vector)
throws MathRuntimeException
Simple constructor. Build a vector from its underlying 3D vector
Parameters:
vector - 3D vector
Throws:
MathRuntimeException - if vector norm is zero
• ### Method Detail

• #### getTheta

public double getTheta()
Get the azimuthal angle $$\theta$$ in the x-y plane.
Returns:
azimuthal angle $$\theta$$ in the x-y plane
S2Point(double, double)
• #### getPhi

public double getPhi()
Get the polar angle $$\varphi$$.
Returns:
polar angle $$\varphi$$
S2Point(double, double)
• #### getVector

public Vector3D getVector()
Get the corresponding normalized vector in the 3D euclidean space.
Returns:
normalized vector
• #### getSpace

public Space getSpace()
Get the space to which the point belongs.
Specified by:
getSpace in interface Point<Sphere2D>
Returns:
containing space
• #### isNaN

public boolean isNaN()
Returns true if any coordinate of this point is NaN; false otherwise
Specified by:
isNaN in interface Point<Sphere2D>
Returns:
true if any coordinate of this point is NaN; false otherwise
• #### negate

public S2Point negate()
Get the opposite of the instance.
Returns:
a new vector which is opposite to the instance
• #### distance

public double distance(Point<Sphere2D> point)
Compute the distance between the instance and another point.
Specified by:
distance in interface Point<Sphere2D>
Parameters:
point - second point
Returns:
the distance between the instance and p
• #### distance

public static double distance(S2Point p1,
S2Point p2)
Compute the distance (angular separation) between two points.
Parameters:
p1 - first vector
p2 - second vector
Returns:
the angular separation between p1 and p2
• #### equals

public boolean equals(Object other)
Test for the equality of two points on the 2-sphere.

If all coordinates of two points are exactly the same, and none are Double.NaN, the two points are considered to be equal.

NaN coordinates are considered to affect globally the point and be equals to each other - i.e, if either (or all) coordinates of the point are equal to Double.NaN, the point is equal to NaN.

Overrides:
equals in class Object
Parameters:
other - Object to test for equality to this
Returns:
true if two points on the 2-sphere objects are equal, false if object is null, not an instance of S2Point, or not equal to this S2Point instance
• #### equalsIeee754

public boolean equalsIeee754(Object other)
Test for the equality of two points on the 2-sphere.

If all coordinates of two points are exactly the same, and none are Double.NaN, the two points are considered to be equal.

In compliance with IEEE754 handling, if any coordinates of any of the two points are NaN, then the points are considered different. This implies that S2Point.NaN.equals(S2Point.NaN) returns false despite the instance is checked against itself.

Parameters:
other - Object to test for equality to this
Returns:
true if two points objects are equal, false if object is null, not an instance of S2Point, or not equal to this S2Point instance
Since:
2.1
• #### hashCode

public int hashCode()
Get a hashCode for the point.

All NaN values have the same hash code.

Overrides:
hashCode in class Object
Returns:
a hash code value for this object
• #### toString

public String toString()
Overrides:
toString in class Object