diff options
Diffstat (limited to 'src/main/java/org/apache/commons/math3/geometry/spherical/twod/S2Point.java')
-rw-r--r-- | src/main/java/org/apache/commons/math3/geometry/spherical/twod/S2Point.java | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/geometry/spherical/twod/S2Point.java b/src/main/java/org/apache/commons/math3/geometry/spherical/twod/S2Point.java new file mode 100644 index 0000000..677e830 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/geometry/spherical/twod/S2Point.java @@ -0,0 +1,237 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.math3.geometry.spherical.twod; + +import org.apache.commons.math3.exception.MathArithmeticException; +import org.apache.commons.math3.exception.OutOfRangeException; +import org.apache.commons.math3.geometry.Point; +import org.apache.commons.math3.geometry.Space; +import org.apache.commons.math3.geometry.euclidean.threed.Vector3D; +import org.apache.commons.math3.util.FastMath; +import org.apache.commons.math3.util.MathUtils; + +/** This class represents a point on the 2-sphere. + * <p> + * 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 <a + * href="http://mathworld.wolfram.com/SphericalCoordinates.html">Spherical + * Coordinates</a> in MathWorld). + * </p> + * <p>Instances of this class are guaranteed to be immutable.</p> + * @since 3.3 + */ +public class S2Point implements Point<Sphere2D> { + + /** +I (coordinates: \( \theta = 0, \varphi = \pi/2 \)). */ + public static final S2Point PLUS_I = new S2Point(0, 0.5 * FastMath.PI, Vector3D.PLUS_I); + + /** +J (coordinates: \( \theta = \pi/2, \varphi = \pi/2 \))). */ + public static final S2Point PLUS_J = new S2Point(0.5 * FastMath.PI, 0.5 * FastMath.PI, Vector3D.PLUS_J); + + /** +K (coordinates: \( \theta = any angle, \varphi = 0 \)). */ + public static final S2Point PLUS_K = new S2Point(0, 0, Vector3D.PLUS_K); + + /** -I (coordinates: \( \theta = \pi, \varphi = \pi/2 \)). */ + public static final S2Point MINUS_I = new S2Point(FastMath.PI, 0.5 * FastMath.PI, Vector3D.MINUS_I); + + /** -J (coordinates: \( \theta = 3\pi/2, \varphi = \pi/2 \)). */ + public static final S2Point MINUS_J = new S2Point(1.5 * FastMath.PI, 0.5 * FastMath.PI, Vector3D.MINUS_J); + + /** -K (coordinates: \( \theta = any angle, \varphi = \pi \)). */ + public static final S2Point MINUS_K = new S2Point(0, FastMath.PI, Vector3D.MINUS_K); + + // CHECKSTYLE: stop ConstantName + /** A vector with all coordinates set to NaN. */ + public static final S2Point NaN = new S2Point(Double.NaN, Double.NaN, Vector3D.NaN); + // CHECKSTYLE: resume ConstantName + + /** Serializable UID. */ + private static final long serialVersionUID = 20131218L; + + /** Azimuthal angle \( \theta \) in the x-y plane. */ + private final double theta; + + /** Polar angle \( \varphi \). */ + private final double phi; + + /** Corresponding 3D normalized vector. */ + private final Vector3D vector; + + /** Simple constructor. + * Build a vector from its spherical coordinates + * @param theta azimuthal angle \( \theta \) in the x-y plane + * @param phi polar angle \( \varphi \) + * @see #getTheta() + * @see #getPhi() + * @exception OutOfRangeException if \( \varphi \) is not in the [\( 0; \pi \)] range + */ + public S2Point(final double theta, final double phi) + throws OutOfRangeException { + this(theta, phi, vector(theta, phi)); + } + + /** Simple constructor. + * Build a vector from its underlying 3D vector + * @param vector 3D vector + * @exception MathArithmeticException if vector norm is zero + */ + public S2Point(final Vector3D vector) throws MathArithmeticException { + this(FastMath.atan2(vector.getY(), vector.getX()), Vector3D.angle(Vector3D.PLUS_K, vector), + vector.normalize()); + } + + /** Build a point from its internal components. + * @param theta azimuthal angle \( \theta \) in the x-y plane + * @param phi polar angle \( \varphi \) + * @param vector corresponding vector + */ + private S2Point(final double theta, final double phi, final Vector3D vector) { + this.theta = theta; + this.phi = phi; + this.vector = vector; + } + + /** Build the normalized vector corresponding to spherical coordinates. + * @param theta azimuthal angle \( \theta \) in the x-y plane + * @param phi polar angle \( \varphi \) + * @return normalized vector + * @exception OutOfRangeException if \( \varphi \) is not in the [\( 0; \pi \)] range + */ + private static Vector3D vector(final double theta, final double phi) + throws OutOfRangeException { + + if (phi < 0 || phi > FastMath.PI) { + throw new OutOfRangeException(phi, 0, FastMath.PI); + } + + final double cosTheta = FastMath.cos(theta); + final double sinTheta = FastMath.sin(theta); + final double cosPhi = FastMath.cos(phi); + final double sinPhi = FastMath.sin(phi); + + return new Vector3D(cosTheta * sinPhi, sinTheta * sinPhi, cosPhi); + + } + + /** Get the azimuthal angle \( \theta \) in the x-y plane. + * @return azimuthal angle \( \theta \) in the x-y plane + * @see #S2Point(double, double) + */ + public double getTheta() { + return theta; + } + + /** Get the polar angle \( \varphi \). + * @return polar angle \( \varphi \) + * @see #S2Point(double, double) + */ + public double getPhi() { + return phi; + } + + /** Get the corresponding normalized vector in the 3D euclidean space. + * @return normalized vector + */ + public Vector3D getVector() { + return vector; + } + + /** {@inheritDoc} */ + public Space getSpace() { + return Sphere2D.getInstance(); + } + + /** {@inheritDoc} */ + public boolean isNaN() { + return Double.isNaN(theta) || Double.isNaN(phi); + } + + /** Get the opposite of the instance. + * @return a new vector which is opposite to the instance + */ + public S2Point negate() { + return new S2Point(-theta, FastMath.PI - phi, vector.negate()); + } + + /** {@inheritDoc} */ + public double distance(final Point<Sphere2D> point) { + return distance(this, (S2Point) point); + } + + /** Compute the distance (angular separation) between two points. + * @param p1 first vector + * @param p2 second vector + * @return the angular separation between p1 and p2 + */ + public static double distance(S2Point p1, S2Point p2) { + return Vector3D.angle(p1.vector, p2.vector); + } + + /** + * Test for the equality of two points on the 2-sphere. + * <p> + * If all coordinates of two points are exactly the same, and none are + * <code>Double.NaN</code>, the two points are considered to be equal. + * </p> + * <p> + * <code>NaN</code> coordinates are considered to affect globally the vector + * and be equals to each other - i.e, if either (or all) coordinates of the + * 2D vector are equal to <code>Double.NaN</code>, the 2D vector is equal to + * {@link #NaN}. + * </p> + * + * @param other Object to test for equality to this + * @return 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 + * + */ + @Override + public boolean equals(Object other) { + + if (this == other) { + return true; + } + + if (other instanceof S2Point) { + final S2Point rhs = (S2Point) other; + if (rhs.isNaN()) { + return this.isNaN(); + } + + return (theta == rhs.theta) && (phi == rhs.phi); + } + return false; + } + + /** + * Get a hashCode for the 2D vector. + * <p> + * All NaN values have the same hash code.</p> + * + * @return a hash code value for this object + */ + @Override + public int hashCode() { + if (isNaN()) { + return 542; + } + return 134 * (37 * MathUtils.hash(theta) + MathUtils.hash(phi)); + } + +} |