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| 1702 | - | 1 | /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- |
| 2 | /* |
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| 3 | * quaternion.cpp |
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| 4 | * Copyright (C) Andrew Tridgell 2012 |
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| 5 | * |
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| 6 | * This file is free software: you can redistribute it and/or modify it |
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| 7 | * under the terms of the GNU General Public License as published by the |
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| 8 | * Free Software Foundation, either version 3 of the License, or |
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| 9 | * (at your option) any later version. |
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| 10 | * |
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| 11 | * This file is distributed in the hope that it will be useful, but |
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| 12 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
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| 14 | * See the GNU General Public License for more details. |
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| 15 | * |
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| 16 | * You should have received a copy of the GNU General Public License along |
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| 17 | * with this program. If not, see <http://www.gnu.org/licenses/>. |
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| 18 | */ |
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| 19 | |||
| 20 | #include "AP_Math.h" |
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| 21 | |||
| 22 | // return the rotation matrix equivalent for this quaternion |
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| 23 | void Quaternion::rotation_matrix(Matrix3f &m) |
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| 24 | { |
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| 25 | float q3q3 = q3 * q3; |
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| 26 | float q3q4 = q3 * q4; |
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| 27 | float q2q2 = q2 * q2; |
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| 28 | float q2q3 = q2 * q3; |
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| 29 | float q2q4 = q2 * q4; |
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| 30 | float q1q2 = q1 * q2; |
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| 31 | float q1q3 = q1 * q3; |
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| 32 | float q1q4 = q1 * q4; |
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| 33 | float q4q4 = q4 * q4; |
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| 34 | |||
| 35 | m.a.x = 1-2*(q3q3 + q4q4); |
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| 36 | m.a.y = 2*(q2q3 - q1q4); |
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| 37 | m.a.z = 2*(q2q4 + q1q3); |
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| 38 | m.b.x = 2*(q2q3 + q1q4); |
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| 39 | m.b.y = 1-2*(q2q2 + q4q4); |
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| 40 | m.b.z = 2*(q3q4 - q1q2); |
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| 41 | m.c.x = 2*(q2q4 - q1q3); |
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| 42 | m.c.y = 2*(q3q4 + q1q2); |
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| 43 | m.c.z = 1-2*(q2q2 + q3q3); |
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| 44 | } |
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| 45 | |||
| 46 | // convert a vector from earth to body frame |
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| 47 | void Quaternion::earth_to_body(Vector3f &v) |
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| 48 | { |
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| 49 | Matrix3f m; |
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| 50 | // we reverse z before and afterwards because of the differing |
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| 51 | // quaternion conventions from APM conventions. |
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| 52 | v.z = -v.z; |
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| 53 | rotation_matrix(m); |
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| 54 | v = m * v; |
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| 55 | v.z = -v.z; |
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| 56 | } |
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| 57 | |||
| 58 | // create a quaternion from Euler angles |
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| 59 | void Quaternion::from_euler(float roll, float pitch, float yaw) |
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| 60 | { |
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| 61 | float cr2 = cos(roll*0.5); |
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| 62 | float cp2 = cos(pitch*0.5); |
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| 63 | float cy2 = cos(yaw*0.5); |
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| 64 | float sr2 = sin(roll*0.5); |
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| 65 | float sp2 = sin(pitch*0.5); |
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| 66 | float sy2 = sin(yaw*0.5); |
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| 67 | |||
| 68 | q1 = cr2*cp2*cy2 + sr2*sp2*sy2; |
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| 69 | q2 = sr2*cp2*cy2 - cr2*sp2*sy2; |
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| 70 | q3 = cr2*sp2*cy2 + sr2*cp2*sy2; |
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| 71 | q4 = cr2*cp2*sy2 - sr2*sp2*cy2; |
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| 72 | } |
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| 73 | |||
| 74 | // create eulers from a quaternion |
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| 75 | void Quaternion::to_euler(float *roll, float *pitch, float *yaw) |
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| 76 | { |
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| 77 | if (roll) { |
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| 78 | *roll = (atan2(2.0*(q1*q2 + q3*q4), |
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| 79 | 1 - 2.0*(q2*q2 + q3*q3))); |
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| 80 | } |
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| 81 | if (pitch) { |
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| 82 | // we let safe_asin() handle the singularities near 90/-90 in pitch |
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| 83 | *pitch = safe_asin(2.0*(q1*q3 - q4*q2)); |
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| 84 | } |
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| 85 | if (yaw) { |
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| 86 | *yaw = atan2(2.0*(q1*q4 + q2*q3), |
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| 87 | 1 - 2.0*(q3*q3 + q4*q4)); |
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| 88 | } |
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| 89 | } |