Rotation.java
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* 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
*
* https://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
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/*
* This is not the original file distributed by the Apache Software Foundation
* It has been modified by the Hipparchus project
*/
package org.hipparchus.geometry.euclidean.threed;
import java.io.Serializable;
import org.hipparchus.exception.MathIllegalArgumentException;
import org.hipparchus.exception.MathRuntimeException;
import org.hipparchus.geometry.LocalizedGeometryFormats;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
import org.hipparchus.util.SinCos;
/**
* This class implements rotations in a three-dimensional space.
*
* <p>Rotations can be represented by several different mathematical
* entities (matrices, axe and angle, Cardan or Euler angles,
* quaternions). This class presents an higher level abstraction, more
* user-oriented and hiding this implementation details. Well, for the
* curious, we use quaternions for the internal representation. The
* user can build a rotation from any of these representations, and
* any of these representations can be retrieved from a
* <code>Rotation</code> instance (see the various constructors and
* getters). In addition, a rotation can also be built implicitly
* from a set of vectors and their image.</p>
* <p>This implies that this class can be used to convert from one
* representation to another one. For example, converting a rotation
* matrix into a set of Cardan angles from can be done using the
* following single line of code:</p>
* <pre>
* double[] angles = new Rotation(matrix, 1.0e-10).getAngles(RotationOrder.XYZ);
* </pre>
* <p>Focus is oriented on what a rotation <em>do</em> rather than on its
* underlying representation. Once it has been built, and regardless of its
* internal representation, a rotation is an <em>operator</em> which basically
* transforms three dimensional {@link Vector3D vectors} into other three
* dimensional {@link Vector3D vectors}. Depending on the application, the
* meaning of these vectors may vary and the semantics of the rotation also.</p>
* <p>For example in an spacecraft attitude simulation tool, users will often
* consider the vectors are fixed (say the Earth direction for example) and the
* frames change. The rotation transforms the coordinates of the vector in inertial
* frame into the coordinates of the same vector in satellite frame. In this
* case, the rotation implicitly defines the relation between the two frames.</p>
* <p>Another example could be a telescope control application, where the rotation
* would transform the sighting direction at rest into the desired observing
* direction when the telescope is pointed towards an object of interest. In this
* case the rotation transforms the direction at rest in a topocentric frame
* into the sighting direction in the same topocentric frame. This implies in this
* case the frame is fixed and the vector moves.</p>
* <p>In many case, both approaches will be combined. In our telescope example,
* we will probably also need to transform the observing direction in the topocentric
* frame into the observing direction in inertial frame taking into account the observatory
* location and the Earth rotation, which would essentially be an application of the
* first approach.</p>
*
* <p>These examples show that a rotation is what the user wants it to be. This
* class does not push the user towards one specific definition and hence does not
* provide methods like <code>projectVectorIntoDestinationFrame</code> or
* <code>computeTransformedDirection</code>. It provides simpler and more generic
* methods: {@link #applyTo(Vector3D) applyTo(Vector3D)} and {@link
* #applyInverseTo(Vector3D) applyInverseTo(Vector3D)}.</p>
*
* <p>Since a rotation is basically a vectorial operator, several rotations can be
* composed together and the composite operation <code>r = r<sub>1</sub> o
* r<sub>2</sub></code> (which means that for each vector <code>u</code>,
* <code>r(u) = r<sub>1</sub>(r<sub>2</sub>(u))</code>) is also a rotation. Hence
* we can consider that in addition to vectors, a rotation can be applied to other
* rotations as well (or to itself). With our previous notations, we would say we
* can apply <code>r<sub>1</sub></code> to <code>r<sub>2</sub></code> and the result
* we get is <code>r = r<sub>1</sub> o r<sub>2</sub></code>. For this purpose, the
* class provides the methods: {@link #applyTo(Rotation) applyTo(Rotation)} and
* {@link #applyInverseTo(Rotation) applyInverseTo(Rotation)}.</p>
*
* <p>Rotations are guaranteed to be immutable objects.</p>
*
* @see Vector3D
* @see RotationOrder
*/
public class Rotation implements Serializable {
/** Identity rotation. */
public static final Rotation IDENTITY = new Rotation(1.0, 0.0, 0.0, 0.0, false);
/** Serializable version identifier */
private static final long serialVersionUID = -2153622329907944313L;
/** Scalar coordinate of the quaternion. */
private final double q0;
/** First coordinate of the vectorial part of the quaternion. */
private final double q1;
/** Second coordinate of the vectorial part of the quaternion. */
private final double q2;
/** Third coordinate of the vectorial part of the quaternion. */
private final double q3;
/** Build a rotation from the quaternion coordinates.
* <p>A rotation can be built from a <em>normalized</em> quaternion,
* i.e. a quaternion for which q<sub>0</sub><sup>2</sup> +
* q<sub>1</sub><sup>2</sup> + q<sub>2</sub><sup>2</sup> +
* q<sub>3</sub><sup>2</sup> = 1. If the quaternion is not normalized,
* the constructor can normalize it in a preprocessing step.</p>
* <p>Note that some conventions put the scalar part of the quaternion
* as the 4<sup>th</sup> component and the vector part as the first three
* components. This is <em>not</em> our convention. We put the scalar part
* as the first component.</p>
* @param q0 scalar part of the quaternion
* @param q1 first coordinate of the vectorial part of the quaternion
* @param q2 second coordinate of the vectorial part of the quaternion
* @param q3 third coordinate of the vectorial part of the quaternion
* @param needsNormalization if true, the coordinates are considered
* not to be normalized, a normalization preprocessing step is performed
* before using them
*/
public Rotation(double q0, double q1, double q2, double q3,
boolean needsNormalization) {
if (needsNormalization) {
// normalization preprocessing
double inv = 1.0 / FastMath.sqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
q0 *= inv;
q1 *= inv;
q2 *= inv;
q3 *= inv;
}
this.q0 = q0;
this.q1 = q1;
this.q2 = q2;
this.q3 = q3;
}
/** Build a rotation from an axis and an angle.
* @param axis axis around which to rotate
* @param angle rotation angle
* @param convention convention to use for the semantics of the angle
* @exception MathIllegalArgumentException if the axis norm is zero
*/
public Rotation(final Vector3D axis, final double angle, final RotationConvention convention)
throws MathIllegalArgumentException {
double norm = axis.getNorm();
if (norm == 0) {
throw new MathIllegalArgumentException(LocalizedGeometryFormats.ZERO_NORM_FOR_ROTATION_AXIS);
}
double halfAngle = convention == RotationConvention.VECTOR_OPERATOR ? -0.5 * angle : 0.5 * angle;
SinCos sinCos = FastMath.sinCos(halfAngle);
double coeff = sinCos.sin() / norm;
q0 = sinCos.cos();
q1 = coeff * axis.getX();
q2 = coeff * axis.getY();
q3 = coeff * axis.getZ();
}
/** Build a rotation from a 3X3 matrix.
* <p>Rotation matrices are orthogonal matrices, i.e. unit matrices
* (which are matrices for which m.m<sup>T</sup> = I) with real
* coefficients. The module of the determinant of unit matrices is
* 1, among the orthogonal 3X3 matrices, only the ones having a
* positive determinant (+1) are rotation matrices.</p>
* <p>When a rotation is defined by a matrix with truncated values
* (typically when it is extracted from a technical sheet where only
* four to five significant digits are available), the matrix is not
* orthogonal anymore. This constructor handles this case
* transparently by using a copy of the given matrix and applying a
* correction to the copy in order to perfect its orthogonality. If
* the Frobenius norm of the correction needed is above the given
* threshold, then the matrix is considered to be too far from a
* true rotation matrix and an exception is thrown.</p>
* @param m rotation matrix
* @param threshold convergence threshold for the iterative
* orthogonality correction (convergence is reached when the
* difference between two steps of the Frobenius norm of the
* correction is below this threshold)
* @exception MathIllegalArgumentException if the matrix is not a 3X3
* matrix, or if it cannot be transformed into an orthogonal matrix
* with the given threshold, or if the determinant of the resulting
* orthogonal matrix is negative
*/
public Rotation(double[][] m, double threshold)
throws MathIllegalArgumentException {
// dimension check
if ((m.length != 3) || (m[0].length != 3) ||
(m[1].length != 3) || (m[2].length != 3)) {
throw new MathIllegalArgumentException(LocalizedGeometryFormats.ROTATION_MATRIX_DIMENSIONS,
m.length, m[0].length);
}
// compute a "close" orthogonal matrix
double[][] ort = orthogonalizeMatrix(m, threshold);
// check the sign of the determinant
double det = ort[0][0] * (ort[1][1] * ort[2][2] - ort[2][1] * ort[1][2]) -
ort[1][0] * (ort[0][1] * ort[2][2] - ort[2][1] * ort[0][2]) +
ort[2][0] * (ort[0][1] * ort[1][2] - ort[1][1] * ort[0][2]);
if (det < 0.0) {
throw new MathIllegalArgumentException(LocalizedGeometryFormats.CLOSEST_ORTHOGONAL_MATRIX_HAS_NEGATIVE_DETERMINANT,
det);
}
double[] quat = mat2quat(ort);
q0 = quat[0];
q1 = quat[1];
q2 = quat[2];
q3 = quat[3];
}
/** Build the rotation that transforms a pair of vectors into another pair.
* <p>Except for possible scale factors, if the instance were applied to
* the pair (u<sub>1</sub>, u<sub>2</sub>) it will produce the pair
* (v<sub>1</sub>, v<sub>2</sub>).</p>
* <p>If the angular separation between u<sub>1</sub> and u<sub>2</sub> is
* not the same as the angular separation between v<sub>1</sub> and
* v<sub>2</sub>, then a corrected v'<sub>2</sub> will be used rather than
* v<sub>2</sub>, the corrected vector will be in the (±v<sub>1</sub>,
* +v<sub>2</sub>) half-plane.</p>
* @param u1 first vector of the origin pair
* @param u2 second vector of the origin pair
* @param v1 desired image of u1 by the rotation
* @param v2 desired image of u2 by the rotation
* @exception MathRuntimeException if the norm of one of the vectors is zero,
* or if one of the pair is degenerated (i.e. the vectors of the pair are collinear)
*/
public Rotation(Vector3D u1, Vector3D u2, Vector3D v1, Vector3D v2)
throws MathRuntimeException {
// build orthonormalized base from u1, u2
// this fails when vectors are null or collinear, which is forbidden to define a rotation
final Vector3D u3 = u1.crossProduct(u2).normalize();
u2 = u3.crossProduct(u1).normalize();
u1 = u1.normalize();
// build an orthonormalized base from v1, v2
// this fails when vectors are null or collinear, which is forbidden to define a rotation
final Vector3D v3 = v1.crossProduct(v2).normalize();
v2 = v3.crossProduct(v1).normalize();
v1 = v1.normalize();
// buid a matrix transforming the first base into the second one
final double[][] m = {
{
MathArrays.linearCombination(u1.getX(), v1.getX(), u2.getX(), v2.getX(), u3.getX(), v3.getX()),
MathArrays.linearCombination(u1.getY(), v1.getX(), u2.getY(), v2.getX(), u3.getY(), v3.getX()),
MathArrays.linearCombination(u1.getZ(), v1.getX(), u2.getZ(), v2.getX(), u3.getZ(), v3.getX())
},
{
MathArrays.linearCombination(u1.getX(), v1.getY(), u2.getX(), v2.getY(), u3.getX(), v3.getY()),
MathArrays.linearCombination(u1.getY(), v1.getY(), u2.getY(), v2.getY(), u3.getY(), v3.getY()),
MathArrays.linearCombination(u1.getZ(), v1.getY(), u2.getZ(), v2.getY(), u3.getZ(), v3.getY())
},
{
MathArrays.linearCombination(u1.getX(), v1.getZ(), u2.getX(), v2.getZ(), u3.getX(), v3.getZ()),
MathArrays.linearCombination(u1.getY(), v1.getZ(), u2.getY(), v2.getZ(), u3.getY(), v3.getZ()),
MathArrays.linearCombination(u1.getZ(), v1.getZ(), u2.getZ(), v2.getZ(), u3.getZ(), v3.getZ())
}
};
double[] quat = mat2quat(m);
q0 = quat[0];
q1 = quat[1];
q2 = quat[2];
q3 = quat[3];
}
/** Build one of the rotations that transform one vector into another one.
* <p>Except for a possible scale factor, if the instance were
* applied to the vector u it will produce the vector v. There is an
* infinite number of such rotations, this constructor choose the
* one with the smallest associated angle (i.e. the one whose axis
* is orthogonal to the (u, v) plane). If u and v are collinear, an
* arbitrary rotation axis is chosen.</p>
* @param u origin vector
* @param v desired image of u by the rotation
* @exception MathRuntimeException if the norm of one of the vectors is zero
*/
public Rotation(Vector3D u, Vector3D v) throws MathRuntimeException {
double normProduct = u.getNorm() * v.getNorm();
if (normProduct == 0) {
throw new MathRuntimeException(LocalizedGeometryFormats.ZERO_NORM_FOR_ROTATION_DEFINING_VECTOR);
}
double dot = u.dotProduct(v);
if (dot < ((2.0e-15 - 1.0) * normProduct)) {
// special case u = -v: we select a PI angle rotation around
// an arbitrary vector orthogonal to u
Vector3D w = u.orthogonal();
q0 = 0.0;
q1 = -w.getX();
q2 = -w.getY();
q3 = -w.getZ();
} else {
// general case: (u, v) defines a plane, we select
// the shortest possible rotation: axis orthogonal to this plane
q0 = FastMath.sqrt(0.5 * (1.0 + dot / normProduct));
double coeff = 1.0 / (2.0 * q0 * normProduct);
Vector3D q = v.crossProduct(u);
q1 = coeff * q.getX();
q2 = coeff * q.getY();
q3 = coeff * q.getZ();
}
}
/** Build a rotation from three Cardan or Euler elementary rotations.
* <p>Cardan rotations are three successive rotations around the
* canonical axes X, Y and Z, each axis being used once. There are
* 6 such sets of rotations (XYZ, XZY, YXZ, YZX, ZXY and ZYX). Euler
* rotations are three successive rotations around the canonical
* axes X, Y and Z, the first and last rotations being around the
* same axis. There are 6 such sets of rotations (XYX, XZX, YXY,
* YZY, ZXZ and ZYZ), the most popular one being ZXZ.</p>
* <p>Beware that many people routinely use the term Euler angles even
* for what really are Cardan angles (this confusion is especially
* widespread in the aerospace business where Roll, Pitch and Yaw angles
* are often wrongly tagged as Euler angles).</p>
* @param order order of rotations to compose, from left to right
* (i.e. we will use {@code r1.compose(r2.compose(r3, convention), convention)})
* @param convention convention to use for the semantics of the angle
* @param alpha1 angle of the first elementary rotation
* @param alpha2 angle of the second elementary rotation
* @param alpha3 angle of the third elementary rotation
*/
public Rotation(RotationOrder order, RotationConvention convention,
double alpha1, double alpha2, double alpha3) {
Rotation r1 = new Rotation(order.getA1(), alpha1, convention);
Rotation r2 = new Rotation(order.getA2(), alpha2, convention);
Rotation r3 = new Rotation(order.getA3(), alpha3, convention);
Rotation composed = r1.compose(r2.compose(r3, convention), convention);
q0 = composed.q0;
q1 = composed.q1;
q2 = composed.q2;
q3 = composed.q3;
}
/** Convert an orthogonal rotation matrix to a quaternion.
* @param ort orthogonal rotation matrix
* @return quaternion corresponding to the matrix
*/
private static double[] mat2quat(final double[][] ort) {
final double[] quat = new double[4];
// There are different ways to compute the quaternions elements
// from the matrix. They all involve computing one element from
// the diagonal of the matrix, and computing the three other ones
// using a formula involving a division by the first element,
// which unfortunately can be zero. Since the norm of the
// quaternion is 1, we know at least one element has an absolute
// value greater or equal to 0.5, so it is always possible to
// select the right formula and avoid division by zero and even
// numerical inaccuracy. Checking the elements in turn and using
// the first one greater than 0.45 is safe (this leads to a simple
// test since qi = 0.45 implies 4 qi^2 - 1 = -0.19)
double s = ort[0][0] + ort[1][1] + ort[2][2];
if (s > -0.19) {
// compute q0 and deduce q1, q2 and q3
quat[0] = 0.5 * FastMath.sqrt(s + 1.0);
double inv = 0.25 / quat[0];
quat[1] = inv * (ort[1][2] - ort[2][1]);
quat[2] = inv * (ort[2][0] - ort[0][2]);
quat[3] = inv * (ort[0][1] - ort[1][0]);
} else {
s = ort[0][0] - ort[1][1] - ort[2][2];
if (s > -0.19) {
// compute q1 and deduce q0, q2 and q3
quat[1] = 0.5 * FastMath.sqrt(s + 1.0);
double inv = 0.25 / quat[1];
quat[0] = inv * (ort[1][2] - ort[2][1]);
quat[2] = inv * (ort[0][1] + ort[1][0]);
quat[3] = inv * (ort[0][2] + ort[2][0]);
} else {
s = ort[1][1] - ort[0][0] - ort[2][2];
if (s > -0.19) {
// compute q2 and deduce q0, q1 and q3
quat[2] = 0.5 * FastMath.sqrt(s + 1.0);
double inv = 0.25 / quat[2];
quat[0] = inv * (ort[2][0] - ort[0][2]);
quat[1] = inv * (ort[0][1] + ort[1][0]);
quat[3] = inv * (ort[2][1] + ort[1][2]);
} else {
// compute q3 and deduce q0, q1 and q2
s = ort[2][2] - ort[0][0] - ort[1][1];
quat[3] = 0.5 * FastMath.sqrt(s + 1.0);
double inv = 0.25 / quat[3];
quat[0] = inv * (ort[0][1] - ort[1][0]);
quat[1] = inv * (ort[0][2] + ort[2][0]);
quat[2] = inv * (ort[2][1] + ort[1][2]);
}
}
}
return quat;
}
/** Revert a rotation.
* Build a rotation which reverse the effect of another
* rotation. This means that if r(u) = v, then r.revert(v) = u. The
* instance is not changed.
* @return a new rotation whose effect is the reverse of the effect
* of the instance
*/
public Rotation revert() {
return new Rotation(-q0, q1, q2, q3, false);
}
/** Get the scalar coordinate of the quaternion.
* @return scalar coordinate of the quaternion
*/
public double getQ0() {
return q0;
}
/** Get the first coordinate of the vectorial part of the quaternion.
* @return first coordinate of the vectorial part of the quaternion
*/
public double getQ1() {
return q1;
}
/** Get the second coordinate of the vectorial part of the quaternion.
* @return second coordinate of the vectorial part of the quaternion
*/
public double getQ2() {
return q2;
}
/** Get the third coordinate of the vectorial part of the quaternion.
* @return third coordinate of the vectorial part of the quaternion
*/
public double getQ3() {
return q3;
}
/** Get the normalized axis of the rotation.
* <p>
* Note that as {@link #getAngle()} always returns an angle
* between 0 and π, changing the convention changes the
* direction of the axis, not the sign of the angle.
* </p>
* @param convention convention to use for the semantics of the angle
* @return normalized axis of the rotation
* @see #Rotation(Vector3D, double, RotationConvention)
*/
public Vector3D getAxis(final RotationConvention convention) {
final double squaredSine = q1 * q1 + q2 * q2 + q3 * q3;
if (squaredSine == 0) {
return convention == RotationConvention.VECTOR_OPERATOR ? Vector3D.PLUS_I : Vector3D.MINUS_I;
} else {
final double sgn = convention == RotationConvention.VECTOR_OPERATOR ? +1 : -1;
if (q0 < 0) {
final double inverse = sgn / FastMath.sqrt(squaredSine);
return new Vector3D(q1 * inverse, q2 * inverse, q3 * inverse);
}
final double inverse = -sgn / FastMath.sqrt(squaredSine);
return new Vector3D(q1 * inverse, q2 * inverse, q3 * inverse);
}
}
/** Get the angle of the rotation.
* @return angle of the rotation (between 0 and π)
* @see #Rotation(Vector3D, double, RotationConvention)
*/
public double getAngle() {
if ((q0 < -0.1) || (q0 > 0.1)) {
return 2 * FastMath.asin(FastMath.sqrt(q1 * q1 + q2 * q2 + q3 * q3));
} else if (q0 < 0) {
return 2 * FastMath.acos(-q0);
}
return 2 * FastMath.acos(q0);
}
/** Get the Cardan or Euler angles corresponding to the instance.
* <p>The equations show that each rotation can be defined by two
* different values of the Cardan or Euler angles set. For example
* if Cardan angles are used, the rotation defined by the angles
* a<sub>1</sub>, a<sub>2</sub> and a<sub>3</sub> is the same as
* the rotation defined by the angles π + a<sub>1</sub>, π
* - a<sub>2</sub> and π + a<sub>3</sub>. This method implements
* the following arbitrary choices:</p>
* <ul>
* <li>for Cardan angles, the chosen set is the one for which the
* second angle is between -π/2 and π/2 (i.e its cosine is
* positive),</li>
* <li>for Euler angles, the chosen set is the one for which the
* second angle is between 0 and π (i.e its sine is positive).</li>
* </ul>
* <p>Cardan and Euler angle have a very disappointing drawback: all
* of them have singularities. This means that if the instance is
* too close to the singularities corresponding to the given
* rotation order, it will be impossible to retrieve the angles. For
* Cardan angles, this is often called gimbal lock. There is
* <em>nothing</em> to do to prevent this, it is an intrinsic problem
* with Cardan and Euler representation (but not a problem with the
* rotation itself, which is perfectly well defined). For Cardan
* angles, singularities occur when the second angle is close to
* -π/2 or +π/2, for Euler angle singularities occur when the
* second angle is close to 0 or π, this implies that the identity
* rotation is always singular for Euler angles!</p>
* @param order rotation order to use
* @param convention convention to use for the semantics of the angle
* @return an array of three angles, in the order specified by the set
*/
public double[] getAngles(RotationOrder order, RotationConvention convention) {
return order.getAngles(this, convention);
}
/** Get the 3X3 matrix corresponding to the instance
* @return the matrix corresponding to the instance
*/
public double[][] getMatrix() {
// products
double q0q0 = q0 * q0;
double q0q1 = q0 * q1;
double q0q2 = q0 * q2;
double q0q3 = q0 * q3;
double q1q1 = q1 * q1;
double q1q2 = q1 * q2;
double q1q3 = q1 * q3;
double q2q2 = q2 * q2;
double q2q3 = q2 * q3;
double q3q3 = q3 * q3;
// create the matrix
double[][] m = new double[3][];
m[0] = new double[3];
m[1] = new double[3];
m[2] = new double[3];
m [0][0] = 2.0 * (q0q0 + q1q1) - 1.0;
m [1][0] = 2.0 * (q1q2 - q0q3);
m [2][0] = 2.0 * (q1q3 + q0q2);
m [0][1] = 2.0 * (q1q2 + q0q3);
m [1][1] = 2.0 * (q0q0 + q2q2) - 1.0;
m [2][1] = 2.0 * (q2q3 - q0q1);
m [0][2] = 2.0 * (q1q3 - q0q2);
m [1][2] = 2.0 * (q2q3 + q0q1);
m [2][2] = 2.0 * (q0q0 + q3q3) - 1.0;
return m;
}
/** Apply the rotation to a vector.
* @param u vector to apply the rotation to
* @return a new vector which is the image of u by the rotation
*/
public Vector3D applyTo(Vector3D u) {
double x = u.getX();
double y = u.getY();
double z = u.getZ();
double s = q1 * x + q2 * y + q3 * z;
return new Vector3D(2 * (q0 * (x * q0 - (q2 * z - q3 * y)) + s * q1) - x,
2 * (q0 * (y * q0 - (q3 * x - q1 * z)) + s * q2) - y,
2 * (q0 * (z * q0 - (q1 * y - q2 * x)) + s * q3) - z);
}
/** Apply the rotation to a vector stored in an array.
* @param in an array with three items which stores vector to rotate
* @param out an array with three items to put result to (it can be the same
* array as in)
*/
public void applyTo(final double[] in, final double[] out) {
final double x = in[0];
final double y = in[1];
final double z = in[2];
final double s = q1 * x + q2 * y + q3 * z;
out[0] = 2 * (q0 * (x * q0 - (q2 * z - q3 * y)) + s * q1) - x;
out[1] = 2 * (q0 * (y * q0 - (q3 * x - q1 * z)) + s * q2) - y;
out[2] = 2 * (q0 * (z * q0 - (q1 * y - q2 * x)) + s * q3) - z;
}
/** Apply the inverse of the rotation to a vector.
* @param u vector to apply the inverse of the rotation to
* @return a new vector which such that u is its image by the rotation
*/
public Vector3D applyInverseTo(Vector3D u) {
double x = u.getX();
double y = u.getY();
double z = u.getZ();
double s = q1 * x + q2 * y + q3 * z;
double m0 = -q0;
return new Vector3D(2 * (m0 * (x * m0 - (q2 * z - q3 * y)) + s * q1) - x,
2 * (m0 * (y * m0 - (q3 * x - q1 * z)) + s * q2) - y,
2 * (m0 * (z * m0 - (q1 * y - q2 * x)) + s * q3) - z);
}
/** Apply the inverse of the rotation to a vector stored in an array.
* @param in an array with three items which stores vector to rotate
* @param out an array with three items to put result to (it can be the same
* array as in)
*/
public void applyInverseTo(final double[] in, final double[] out) {
final double x = in[0];
final double y = in[1];
final double z = in[2];
final double s = q1 * x + q2 * y + q3 * z;
final double m0 = -q0;
out[0] = 2 * (m0 * (x * m0 - (q2 * z - q3 * y)) + s * q1) - x;
out[1] = 2 * (m0 * (y * m0 - (q3 * x - q1 * z)) + s * q2) - y;
out[2] = 2 * (m0 * (z * m0 - (q1 * y - q2 * x)) + s * q3) - z;
}
/** Apply the instance to another rotation.
* <p>
* Calling this method is equivalent to call
* {@link #compose(Rotation, RotationConvention)
* compose(r, RotationConvention.VECTOR_OPERATOR)}.
* </p>
* @param r rotation to apply the rotation to
* @return a new rotation which is the composition of r by the instance
*/
public Rotation applyTo(Rotation r) {
return compose(r, RotationConvention.VECTOR_OPERATOR);
}
/** Compose the instance with another rotation.
* <p>
* If the semantics of the rotations composition corresponds to a
* {@link RotationConvention#VECTOR_OPERATOR vector operator} convention,
* applying the instance to a rotation is computing the composition
* in an order compliant with the following rule : let {@code u} be any
* vector and {@code v} its image by {@code r1} (i.e.
* {@code r1.applyTo(u) = v}). Let {@code w} be the image of {@code v} by
* rotation {@code r2} (i.e. {@code r2.applyTo(v) = w}). Then
* {@code w = comp.applyTo(u)}, where
* {@code comp = r2.compose(r1, RotationConvention.VECTOR_OPERATOR)}.
* </p>
* <p>
* If the semantics of the rotations composition corresponds to a
* {@link RotationConvention#FRAME_TRANSFORM frame transform} convention,
* the application order will be reversed. So keeping the exact same
* meaning of all {@code r1}, {@code r2}, {@code u}, {@code v}, {@code w}
* and {@code comp} as above, {@code comp} could also be computed as
* {@code comp = r1.compose(r2, RotationConvention.FRAME_TRANSFORM)}.
* </p>
* @param r rotation to apply the rotation to
* @param convention convention to use for the semantics of the angle
* @return a new rotation which is the composition of r by the instance
*/
public Rotation compose(final Rotation r, final RotationConvention convention) {
return convention == RotationConvention.VECTOR_OPERATOR ?
composeInternal(r) : r.composeInternal(this);
}
/** Compose the instance with another rotation using vector operator convention.
* @param r rotation to apply the rotation to
* @return a new rotation which is the composition of r by the instance
* using vector operator convention
*/
private Rotation composeInternal(final Rotation r) {
return new Rotation(r.q0 * q0 - (r.q1 * q1 + r.q2 * q2 + r.q3 * q3),
r.q1 * q0 + r.q0 * q1 + (r.q2 * q3 - r.q3 * q2),
r.q2 * q0 + r.q0 * q2 + (r.q3 * q1 - r.q1 * q3),
r.q3 * q0 + r.q0 * q3 + (r.q1 * q2 - r.q2 * q1),
false);
}
/** Apply the inverse of the instance to another rotation.
* <p>
* Calling this method is equivalent to call
* {@link #composeInverse(Rotation, RotationConvention)
* composeInverse(r, RotationConvention.VECTOR_OPERATOR)}.
* </p>
* @param r rotation to apply the rotation to
* @return a new rotation which is the composition of r by the inverse
* of the instance
*/
public Rotation applyInverseTo(Rotation r) {
return composeInverse(r, RotationConvention.VECTOR_OPERATOR);
}
/** Compose the inverse of the instance with another rotation.
* <p>
* If the semantics of the rotations composition corresponds to a
* {@link RotationConvention#VECTOR_OPERATOR vector operator} convention,
* applying the inverse of the instance to a rotation is computing
* the composition in an order compliant with the following rule :
* let {@code u} be any vector and {@code v} its image by {@code r1}
* (i.e. {@code r1.applyTo(u) = v}). Let {@code w} be the inverse image
* of {@code v} by {@code r2} (i.e. {@code r2.applyInverseTo(v) = w}).
* Then {@code w = comp.applyTo(u)}, where
* {@code comp = r2.composeInverse(r1)}.
* </p>
* <p>
* If the semantics of the rotations composition corresponds to a
* {@link RotationConvention#FRAME_TRANSFORM frame transform} convention,
* the application order will be reversed, which means it is the
* <em>innermost</em> rotation that will be reversed. So keeping the exact same
* meaning of all {@code r1}, {@code r2}, {@code u}, {@code v}, {@code w}
* and {@code comp} as above, {@code comp} could also be computed as
* {@code comp = r1.revert().composeInverse(r2.revert(), RotationConvention.FRAME_TRANSFORM)}.
* </p>
* @param r rotation to apply the rotation to
* @param convention convention to use for the semantics of the angle
* @return a new rotation which is the composition of r by the inverse
* of the instance
*/
public Rotation composeInverse(final Rotation r, final RotationConvention convention) {
return convention == RotationConvention.VECTOR_OPERATOR ?
composeInverseInternal(r) : r.composeInternal(revert());
}
/** Compose the inverse of the instance with another rotation
* using vector operator convention.
* @param r rotation to apply the rotation to
* @return a new rotation which is the composition of r by the inverse
* of the instance using vector operator convention
*/
private Rotation composeInverseInternal(Rotation r) {
return new Rotation(-r.q0 * q0 - (r.q1 * q1 + r.q2 * q2 + r.q3 * q3),
-r.q1 * q0 + r.q0 * q1 + (r.q2 * q3 - r.q3 * q2),
-r.q2 * q0 + r.q0 * q2 + (r.q3 * q1 - r.q1 * q3),
-r.q3 * q0 + r.q0 * q3 + (r.q1 * q2 - r.q2 * q1),
false);
}
/** Perfect orthogonality on a 3X3 matrix.
* @param m initial matrix (not exactly orthogonal)
* @param threshold convergence threshold for the iterative
* orthogonality correction (convergence is reached when the
* difference between two steps of the Frobenius norm of the
* correction is below this threshold)
* @return an orthogonal matrix close to m
* @exception MathIllegalArgumentException if the matrix cannot be
* orthogonalized with the given threshold after 10 iterations
*/
private double[][] orthogonalizeMatrix(double[][] m, double threshold)
throws MathIllegalArgumentException {
double[] m0 = m[0];
double[] m1 = m[1];
double[] m2 = m[2];
double x00 = m0[0];
double x01 = m0[1];
double x02 = m0[2];
double x10 = m1[0];
double x11 = m1[1];
double x12 = m1[2];
double x20 = m2[0];
double x21 = m2[1];
double x22 = m2[2];
double fn = 0;
double fn1;
double[][] o = new double[3][3];
double[] o0 = o[0];
double[] o1 = o[1];
double[] o2 = o[2];
// iterative correction: Xn+1 = Xn - 0.5 * (Xn.Mt.Xn - M)
int i;
for (i = 0; i < 11; ++i) {
// Mt.Xn
double mx00 = m0[0] * x00 + m1[0] * x10 + m2[0] * x20;
double mx10 = m0[1] * x00 + m1[1] * x10 + m2[1] * x20;
double mx20 = m0[2] * x00 + m1[2] * x10 + m2[2] * x20;
double mx01 = m0[0] * x01 + m1[0] * x11 + m2[0] * x21;
double mx11 = m0[1] * x01 + m1[1] * x11 + m2[1] * x21;
double mx21 = m0[2] * x01 + m1[2] * x11 + m2[2] * x21;
double mx02 = m0[0] * x02 + m1[0] * x12 + m2[0] * x22;
double mx12 = m0[1] * x02 + m1[1] * x12 + m2[1] * x22;
double mx22 = m0[2] * x02 + m1[2] * x12 + m2[2] * x22;
// Xn+1
o0[0] = x00 - 0.5 * (x00 * mx00 + x01 * mx10 + x02 * mx20 - m0[0]);
o0[1] = x01 - 0.5 * (x00 * mx01 + x01 * mx11 + x02 * mx21 - m0[1]);
o0[2] = x02 - 0.5 * (x00 * mx02 + x01 * mx12 + x02 * mx22 - m0[2]);
o1[0] = x10 - 0.5 * (x10 * mx00 + x11 * mx10 + x12 * mx20 - m1[0]);
o1[1] = x11 - 0.5 * (x10 * mx01 + x11 * mx11 + x12 * mx21 - m1[1]);
o1[2] = x12 - 0.5 * (x10 * mx02 + x11 * mx12 + x12 * mx22 - m1[2]);
o2[0] = x20 - 0.5 * (x20 * mx00 + x21 * mx10 + x22 * mx20 - m2[0]);
o2[1] = x21 - 0.5 * (x20 * mx01 + x21 * mx11 + x22 * mx21 - m2[1]);
o2[2] = x22 - 0.5 * (x20 * mx02 + x21 * mx12 + x22 * mx22 - m2[2]);
// correction on each elements
double corr00 = o0[0] - m0[0];
double corr01 = o0[1] - m0[1];
double corr02 = o0[2] - m0[2];
double corr10 = o1[0] - m1[0];
double corr11 = o1[1] - m1[1];
double corr12 = o1[2] - m1[2];
double corr20 = o2[0] - m2[0];
double corr21 = o2[1] - m2[1];
double corr22 = o2[2] - m2[2];
// Frobenius norm of the correction
fn1 = corr00 * corr00 + corr01 * corr01 + corr02 * corr02 +
corr10 * corr10 + corr11 * corr11 + corr12 * corr12 +
corr20 * corr20 + corr21 * corr21 + corr22 * corr22;
// convergence test
if (FastMath.abs(fn1 - fn) <= threshold) {
return o;
}
// prepare next iteration
x00 = o0[0];
x01 = o0[1];
x02 = o0[2];
x10 = o1[0];
x11 = o1[1];
x12 = o1[2];
x20 = o2[0];
x21 = o2[1];
x22 = o2[2];
fn = fn1;
}
// the algorithm did not converge after 10 iterations
throw new MathIllegalArgumentException(LocalizedGeometryFormats.UNABLE_TO_ORTHOGONOLIZE_MATRIX,
i - 1);
}
/** Compute the <i>distance</i> between two rotations.
* <p>The <i>distance</i> is intended here as a way to check if two
* rotations are almost similar (i.e. they transform vectors the same way)
* or very different. It is mathematically defined as the angle of
* the rotation r that prepended to one of the rotations gives the other
* one: \(r_1(r) = r_2\)
* </p>
* <p>This distance is an angle between 0 and π. Its value is the smallest
* possible upper bound of the angle in radians between r<sub>1</sub>(v)
* and r<sub>2</sub>(v) for all possible vectors v. This upper bound is
* reached for some v. The distance is equal to 0 if and only if the two
* rotations are identical.</p>
* <p>Comparing two rotations should always be done using this value rather
* than for example comparing the components of the quaternions. It is much
* more stable, and has a geometric meaning. Also comparing quaternions
* components is error prone since for example quaternions (0.36, 0.48, -0.48, -0.64)
* and (-0.36, -0.48, 0.48, 0.64) represent exactly the same rotation despite
* their components are different (they are exact opposites).</p>
* @param r1 first rotation
* @param r2 second rotation
* @return <i>distance</i> between r1 and r2
*/
public static double distance(Rotation r1, Rotation r2) {
return r1.composeInverseInternal(r2).getAngle();
}
}