1 | /************************************************************************* |
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2 | * * |
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3 | * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith. * |
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4 | * All rights reserved. Email: russ@q12.org Web: www.q12.org * |
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5 | * * |
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6 | * This library is free software; you can redistribute it and/or * |
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7 | * modify it under the terms of EITHER: * |
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8 | * (1) The GNU Lesser General Public License as published by the Free * |
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9 | * Software Foundation; either version 2.1 of the License, or (at * |
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10 | * your option) any later version. The text of the GNU Lesser * |
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11 | * General Public License is included with this library in the * |
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12 | * file LICENSE.TXT. * |
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13 | * (2) The BSD-style license that is included with this library in * |
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14 | * the file LICENSE-BSD.TXT. * |
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15 | * * |
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16 | * This library is distributed in the hope that it will be useful, * |
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17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of * |
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18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files * |
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19 | * LICENSE.TXT and LICENSE-BSD.TXT for more details. * |
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20 | * * |
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21 | *************************************************************************/ |
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22 | |
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23 | /* |
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24 | |
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25 | test that the rotational physics is correct. |
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26 | |
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27 | an "anchor body" has a number of other randomly positioned bodies |
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28 | ("particles") attached to it by ball-and-socket joints, giving it some |
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29 | random effective inertia tensor. the effective inertia matrix is calculated, |
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30 | and then this inertia is assigned to another "test" body. a random torque is |
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31 | applied to both bodies and the difference in angular velocity and orientation |
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32 | is observed after a number of iterations. |
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33 | |
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34 | typical errors for each test cycle are about 1e-5 ... 1e-4. |
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35 | |
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36 | */ |
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37 | |
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38 | |
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39 | #include <time.h> |
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40 | #include <ode/ode.h> |
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41 | #include <drawstuff/drawstuff.h> |
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42 | |
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43 | #ifdef _MSC_VER |
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44 | #pragma warning(disable:4244 4305) // for VC++, no precision loss complaints |
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45 | #endif |
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46 | |
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47 | // select correct drawing functions |
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48 | |
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49 | #ifdef dDOUBLE |
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50 | #define dsDrawBox dsDrawBoxD |
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51 | #define dsDrawSphere dsDrawSphereD |
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52 | #define dsDrawCylinder dsDrawCylinderD |
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53 | #define dsDrawCapsule dsDrawCapsuleD |
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54 | #endif |
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55 | |
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56 | |
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57 | // some constants |
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58 | |
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59 | #define NUM 10 // number of particles |
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60 | #define SIDE 0.1 // visual size of the particles |
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61 | |
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62 | |
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63 | // dynamics objects an globals |
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64 | |
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65 | static dWorldID world=0; |
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66 | static dBodyID anchor_body,particle[NUM],test_body; |
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67 | static dJointID particle_joint[NUM]; |
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68 | static dReal torque[3]; |
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69 | static int iteration; |
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70 | |
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71 | |
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72 | // start simulation - set viewpoint |
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73 | |
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74 | static void start() |
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75 | { |
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76 | static float xyz[3] = {1.5572f,-1.8886f,1.5700f}; |
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77 | static float hpr[3] = {118.5000f,-17.0000f,0.0000f}; |
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78 | dsSetViewpoint (xyz,hpr); |
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79 | } |
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80 | |
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81 | |
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82 | // compute the mass parameters of a particle set. q = particle positions, |
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83 | // pm = particle masses |
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84 | |
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85 | #define _I(i,j) I[(i)*4+(j)] |
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86 | |
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87 | void computeMassParams (dMass *m, dReal q[NUM][3], dReal pm[NUM]) |
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88 | { |
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89 | int i,j; |
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90 | dMassSetZero (m); |
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91 | for (i=0; i<NUM; i++) { |
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92 | m->mass += pm[i]; |
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93 | for (j=0; j<3; j++) m->c[j] += pm[i]*q[i][j]; |
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94 | m->_I(0,0) += pm[i]*(q[i][1]*q[i][1] + q[i][2]*q[i][2]); |
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95 | m->_I(1,1) += pm[i]*(q[i][0]*q[i][0] + q[i][2]*q[i][2]); |
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96 | m->_I(2,2) += pm[i]*(q[i][0]*q[i][0] + q[i][1]*q[i][1]); |
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97 | m->_I(0,1) -= pm[i]*(q[i][0]*q[i][1]); |
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98 | m->_I(0,2) -= pm[i]*(q[i][0]*q[i][2]); |
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99 | m->_I(1,2) -= pm[i]*(q[i][1]*q[i][2]); |
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100 | } |
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101 | for (j=0; j<3; j++) m->c[j] /= m->mass; |
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102 | m->_I(1,0) = m->_I(0,1); |
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103 | m->_I(2,0) = m->_I(0,2); |
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104 | m->_I(2,1) = m->_I(1,2); |
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105 | } |
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106 | |
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107 | |
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108 | void reset_test() |
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109 | { |
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110 | int i; |
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111 | dMass m,anchor_m; |
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112 | dReal q[NUM][3], pm[NUM]; // particle positions and masses |
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113 | dReal pos1[3] = {1,0,1}; // point of reference (POR) |
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114 | dReal pos2[3] = {-1,0,1}; // point of reference (POR) |
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115 | |
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116 | // make random particle positions (relative to POR) and masses |
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117 | for (i=0; i<NUM; i++) { |
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118 | pm[i] = dRandReal()+0.1; |
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119 | q[i][0] = dRandReal()-0.5; |
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120 | q[i][1] = dRandReal()-0.5; |
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121 | q[i][2] = dRandReal()-0.5; |
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122 | } |
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123 | |
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124 | // adjust particle positions so centor of mass = POR |
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125 | computeMassParams (&m,q,pm); |
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126 | for (i=0; i<NUM; i++) { |
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127 | q[i][0] -= m.c[0]; |
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128 | q[i][1] -= m.c[1]; |
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129 | q[i][2] -= m.c[2]; |
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130 | } |
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131 | |
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132 | if (world) dWorldDestroy (world); |
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133 | world = dWorldCreate(); |
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134 | |
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135 | anchor_body = dBodyCreate (world); |
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136 | dBodySetPosition (anchor_body,pos1[0],pos1[1],pos1[2]); |
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137 | dMassSetBox (&anchor_m,1,SIDE,SIDE,SIDE); |
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138 | dMassAdjust (&anchor_m,0.1); |
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139 | dBodySetMass (anchor_body,&anchor_m); |
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140 | |
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141 | for (i=0; i<NUM; i++) { |
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142 | particle[i] = dBodyCreate (world); |
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143 | dBodySetPosition (particle[i], |
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144 | pos1[0]+q[i][0],pos1[1]+q[i][1],pos1[2]+q[i][2]); |
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145 | dMassSetBox (&m,1,SIDE,SIDE,SIDE); |
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146 | dMassAdjust (&m,pm[i]); |
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147 | dBodySetMass (particle[i],&m); |
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148 | } |
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149 | |
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150 | for (i=0; i < NUM; i++) { |
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151 | particle_joint[i] = dJointCreateBall (world,0); |
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152 | dJointAttach (particle_joint[i],anchor_body,particle[i]); |
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153 | const dReal *p = dBodyGetPosition (particle[i]); |
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154 | dJointSetBallAnchor (particle_joint[i],p[0],p[1],p[2]); |
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155 | } |
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156 | |
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157 | // make test_body with the same mass and inertia of the anchor_body plus |
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158 | // all the particles |
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159 | |
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160 | test_body = dBodyCreate (world); |
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161 | dBodySetPosition (test_body,pos2[0],pos2[1],pos2[2]); |
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162 | computeMassParams (&m,q,pm); |
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163 | m.mass += anchor_m.mass; |
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164 | for (i=0; i<12; i++) m.I[i] = m.I[i] + anchor_m.I[i]; |
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165 | dBodySetMass (test_body,&m); |
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166 | |
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167 | // rotate the test and anchor bodies by a random amount |
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168 | dQuaternion qrot; |
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169 | for (i=0; i<4; i++) qrot[i] = dRandReal()-0.5; |
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170 | dNormalize4 (qrot); |
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171 | dBodySetQuaternion (anchor_body,qrot); |
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172 | dBodySetQuaternion (test_body,qrot); |
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173 | dMatrix3 R; |
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174 | dQtoR (qrot,R); |
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175 | for (i=0; i<NUM; i++) { |
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176 | dVector3 v; |
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177 | dMultiply0 (v,R,&q[i][0],3,3,1); |
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178 | dBodySetPosition (particle[i],pos1[0]+v[0],pos1[1]+v[1],pos1[2]+v[2]); |
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179 | } |
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180 | |
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181 | // set random torque |
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182 | for (i=0; i<3; i++) torque[i] = (dRandReal()-0.5) * 0.1; |
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183 | |
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184 | |
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185 | iteration=0; |
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186 | } |
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187 | |
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188 | |
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189 | // simulation loop |
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190 | |
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191 | static void simLoop (int pause) |
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192 | { |
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193 | if (!pause) { |
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194 | dBodyAddTorque (anchor_body,torque[0],torque[1],torque[2]); |
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195 | dBodyAddTorque (test_body,torque[0],torque[1],torque[2]); |
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196 | dWorldStep (world,0.03); |
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197 | |
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198 | iteration++; |
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199 | if (iteration >= 100) { |
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200 | // measure the difference between the anchor and test bodies |
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201 | const dReal *w1 = dBodyGetAngularVel (anchor_body); |
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202 | const dReal *w2 = dBodyGetAngularVel (test_body); |
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203 | const dReal *q1 = dBodyGetQuaternion (anchor_body); |
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204 | const dReal *q2 = dBodyGetQuaternion (test_body); |
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205 | dReal maxdiff = dMaxDifference (w1,w2,1,3); |
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206 | printf ("w-error = %.4e (%.2f,%.2f,%.2f) and (%.2f,%.2f,%.2f)\n", |
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207 | maxdiff,w1[0],w1[1],w1[2],w2[0],w2[1],w2[2]); |
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208 | maxdiff = dMaxDifference (q1,q2,1,4); |
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209 | printf ("q-error = %.4e\n",maxdiff); |
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210 | reset_test(); |
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211 | } |
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212 | } |
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213 | |
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214 | dReal sides[3] = {SIDE,SIDE,SIDE}; |
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215 | dReal sides2[3] = {6*SIDE,6*SIDE,6*SIDE}; |
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216 | dReal sides3[3] = {3*SIDE,3*SIDE,3*SIDE}; |
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217 | dsSetColor (1,1,1); |
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218 | dsDrawBox (dBodyGetPosition(anchor_body), dBodyGetRotation(anchor_body), |
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219 | sides3); |
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220 | dsSetColor (1,0,0); |
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221 | dsDrawBox (dBodyGetPosition(test_body), dBodyGetRotation(test_body), sides2); |
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222 | dsSetColor (1,1,0); |
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223 | for (int i=0; i<NUM; i++) |
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224 | dsDrawBox (dBodyGetPosition (particle[i]), |
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225 | dBodyGetRotation (particle[i]), sides); |
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226 | } |
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227 | |
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228 | |
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229 | int main (int argc, char **argv) |
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230 | { |
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231 | // setup pointers to drawstuff callback functions |
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232 | dsFunctions fn; |
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233 | fn.version = DS_VERSION; |
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234 | fn.start = &start; |
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235 | fn.step = &simLoop; |
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236 | fn.command = 0; |
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237 | fn.stop = 0; |
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238 | fn.path_to_textures = "../../drawstuff/textures"; |
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239 | if(argc==2) |
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240 | { |
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241 | fn.path_to_textures = argv[1]; |
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242 | } |
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243 | |
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244 | dInitODE(); |
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245 | dRandSetSeed (time(0)); |
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246 | reset_test(); |
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247 | |
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248 | // run simulation |
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249 | dsSimulationLoop (argc,argv,352,288,&fn); |
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250 | |
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251 | dWorldDestroy (world); |
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252 | dCloseODE(); |
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253 | return 0; |
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254 | } |
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