georegression.transform.se.AverageQuaternion_F64 Maven / Gradle / Ivy
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GeoRegression is a free Java based geometry library for scientific computing in fields such as robotics and computer vision with a focus on 2D/3D space.
/*
* Copyright (C) 2011-2017, Peter Abeles. All Rights Reserved.
*
* This file is part of Geometric Regression Library (GeoRegression).
*
* Licensed 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 georegression.transform.se;
import georegression.struct.so.Quaternion_F64;
import org.ejml.data.DMatrixRMaj;
import org.ejml.dense.row.factory.DecompositionFactory_DDRM;
import org.ejml.interfaces.decomposition.EigenDecomposition_F64;
import java.util.List;
/**
* Finds the average of a set of {@link Quaternion_F64 quaternions} by using a method proposed in [1].
*
* [1] MLA Markley, F. Landis, et al. "Quaternion averaging." (2007)
*
* @author Peter Abeles
*/
public class AverageQuaternion_F64 {
DMatrixRMaj M = new DMatrixRMaj(4,4);
EigenDecomposition_F64 eig = DecompositionFactory_DDRM.eig(4,true,true);
public boolean process(List list , Quaternion_F64 average ) {
if( list.isEmpty() )
throw new IllegalArgumentException("Input list is empty");
if( average == null )
throw new IllegalArgumentException("average is null");
M.zero();
for (int i = 0; i < list.size(); i++) {
Quaternion_F64 q = list.get(i);
// Perform M = M + q*q^T
// Where q is a column [w,x,y,z] vector
// row 0
M.data[0] += q.w*q.w; M.data[1] += q.w*q.x; M.data[2] += q.w*q.y; M.data[3] += q.w*q.z;
// row 1
M.data[4] += q.x*q.w; M.data[5] += q.x*q.x; M.data[6] += q.x*q.y; M.data[7] += q.x*q.z;
// row 2
M.data[8] += q.y*q.w; M.data[9] += q.y*q.x; M.data[10] += q.y*q.y; M.data[11] += q.y*q.z;
// row 3
M.data[12] += q.z*q.w; M.data[13] += q.z*q.x; M.data[14] += q.z*q.y; M.data[15] += q.z*q.z;
}
if( !eig.decompose(M) )
return false;
// the largest eigenvector is the quaternion
int largest = 0;
double largestMag = eig.getEigenvalue(0).getMagnitude2();
for (int i = 1; i < 4; i++) {
double mag = eig.getEigenvalue(i).getMagnitude2();
if( mag > largestMag ) {
largestMag = mag;
largest = i;
}
}
DMatrixRMaj v = eig.getEigenVector(largest);
// this will be a normalized quaternion due to properties of eigenvectors
average.w = (double) v.get(0);
average.x = (double) v.get(1);
average.y = (double) v.get(2);
average.z = (double) v.get(3);
return true;
}
}