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89 lines
2.6 KiB
89 lines
2.6 KiB
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- |
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/* |
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* quaternion.cpp |
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* Copyright (C) Andrew Tridgell 2012 |
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* |
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* This file is free software: you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License as published by the |
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* Free Software Foundation, either version 3 of the License, or |
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* (at your option) any later version. |
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* |
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* This file is distributed in the hope that it will be useful, but |
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* WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
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* See the GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License along |
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* with this program. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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#include "AP_Math.h" |
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// return the rotation matrix equivalent for this quaternion |
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void Quaternion::rotation_matrix(Matrix3f &m) |
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{ |
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float q3q3 = q3 * q3; |
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float q3q4 = q3 * q4; |
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float q2q2 = q2 * q2; |
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float q2q3 = q2 * q3; |
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float q2q4 = q2 * q4; |
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float q1q2 = q1 * q2; |
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float q1q3 = q1 * q3; |
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float q1q4 = q1 * q4; |
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float q4q4 = q4 * q4; |
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m.a.x = 1-2*(q3q3 + q4q4); |
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m.a.y = 2*(q2q3 - q1q4); |
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m.a.z = 2*(q2q4 + q1q3); |
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m.b.x = 2*(q2q3 + q1q4); |
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m.b.y = 1-2*(q2q2 + q4q4); |
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m.b.z = 2*(q3q4 - q1q2); |
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m.c.x = 2*(q2q4 - q1q3); |
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m.c.y = 2*(q3q4 + q1q2); |
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m.c.z = 1-2*(q2q2 + q3q3); |
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} |
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// convert a vector from earth to body frame |
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void Quaternion::earth_to_body(Vector3f &v) |
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{ |
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Matrix3f m; |
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// we reverse z before and afterwards because of the differing |
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// quaternion conventions from APM conventions. |
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v.z = -v.z; |
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rotation_matrix(m); |
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v = m * v; |
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v.z = -v.z; |
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} |
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// create a quaternion from Euler angles |
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void Quaternion::from_euler(float roll, float pitch, float yaw) |
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{ |
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float cr2 = cosf(roll*0.5f); |
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float cp2 = cosf(pitch*0.5f); |
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float cy2 = cosf(yaw*0.5f); |
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float sr2 = sinf(roll*0.5f); |
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float sp2 = sinf(pitch*0.5f); |
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float sy2 = sinf(yaw*0.5f); |
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q1 = cr2*cp2*cy2 + sr2*sp2*sy2; |
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q2 = sr2*cp2*cy2 - cr2*sp2*sy2; |
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q3 = cr2*sp2*cy2 + sr2*cp2*sy2; |
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q4 = cr2*cp2*sy2 - sr2*sp2*cy2; |
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} |
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// create eulers from a quaternion |
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void Quaternion::to_euler(float *roll, float *pitch, float *yaw) |
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{ |
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if (roll) { |
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*roll = (atan2f(2.0f*(q1*q2 + q3*q4), |
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1 - 2.0f*(q2*q2 + q3*q3))); |
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} |
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if (pitch) { |
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// we let safe_asin() handle the singularities near 90/-90 in pitch |
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*pitch = safe_asin(2.0f*(q1*q3 - q4*q2)); |
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} |
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if (yaw) { |
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*yaw = atan2f(2.0f*(q1*q4 + q2*q3), |
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1 - 2.0f*(q3*q3 + q4*q4)); |
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} |
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}
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