255 lines
7.7 KiB
C++
255 lines
7.7 KiB
C++
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/*************************************************************************
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* *
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* Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith. *
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* All rights reserved. Email: russ@q12.org Web: www.q12.org *
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* *
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* This library is free software; you can redistribute it and/or *
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* modify it under the terms of EITHER: *
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* (1) The GNU Lesser General Public License as published by the Free *
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* Software Foundation; either version 2.1 of the License, or (at *
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* your option) any later version. The text of the GNU Lesser *
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* General Public License is included with this library in the *
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* file LICENSE.TXT. *
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* (2) The BSD-style license that is included with this library in *
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* the file LICENSE-BSD.TXT. *
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* *
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* This library is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files *
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* LICENSE.TXT and LICENSE-BSD.TXT for more details. *
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* *
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*************************************************************************/
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/*
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test that the rotational physics is correct.
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an "anchor body" has a number of other randomly positioned bodies
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("particles") attached to it by ball-and-socket joints, giving it some
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random effective inertia tensor. the effective inertia matrix is calculated,
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and then this inertia is assigned to another "test" body. a random torque is
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applied to both bodies and the difference in angular velocity and orientation
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is observed after a number of iterations.
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typical errors for each test cycle are about 1e-5 ... 1e-4.
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*/
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#include <time.h>
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#include <ode/ode.h>
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#include <drawstuff/drawstuff.h>
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#ifdef _MSC_VER
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#pragma warning(disable:4244 4305) // for VC++, no precision loss complaints
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#endif
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// select correct drawing functions
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#ifdef dDOUBLE
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#define dsDrawBox dsDrawBoxD
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#define dsDrawSphere dsDrawSphereD
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#define dsDrawCylinder dsDrawCylinderD
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#define dsDrawCapsule dsDrawCapsuleD
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#endif
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// some constants
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#define NUM 10 // number of particles
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#define SIDE 0.1 // visual size of the particles
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// dynamics objects an globals
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static dWorldID world=0;
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static dBodyID anchor_body,particle[NUM],test_body;
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static dJointID particle_joint[NUM];
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static dReal torque[3];
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static int iteration;
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// start simulation - set viewpoint
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static void start()
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{
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static float xyz[3] = {1.5572f,-1.8886f,1.5700f};
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static float hpr[3] = {118.5000f,-17.0000f,0.0000f};
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dsSetViewpoint (xyz,hpr);
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}
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// compute the mass parameters of a particle set. q = particle positions,
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// pm = particle masses
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#define _I(i,j) I[(i)*4+(j)]
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void computeMassParams (dMass *m, dReal q[NUM][3], dReal pm[NUM])
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{
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int i,j;
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dMassSetZero (m);
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for (i=0; i<NUM; i++) {
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m->mass += pm[i];
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for (j=0; j<3; j++) m->c[j] += pm[i]*q[i][j];
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m->_I(0,0) += pm[i]*(q[i][1]*q[i][1] + q[i][2]*q[i][2]);
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m->_I(1,1) += pm[i]*(q[i][0]*q[i][0] + q[i][2]*q[i][2]);
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m->_I(2,2) += pm[i]*(q[i][0]*q[i][0] + q[i][1]*q[i][1]);
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m->_I(0,1) -= pm[i]*(q[i][0]*q[i][1]);
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m->_I(0,2) -= pm[i]*(q[i][0]*q[i][2]);
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m->_I(1,2) -= pm[i]*(q[i][1]*q[i][2]);
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}
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for (j=0; j<3; j++) m->c[j] /= m->mass;
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m->_I(1,0) = m->_I(0,1);
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m->_I(2,0) = m->_I(0,2);
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m->_I(2,1) = m->_I(1,2);
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}
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void reset_test()
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{
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int i;
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dMass m,anchor_m;
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dReal q[NUM][3], pm[NUM]; // particle positions and masses
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dReal pos1[3] = {1,0,1}; // point of reference (POR)
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dReal pos2[3] = {-1,0,1}; // point of reference (POR)
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// make random particle positions (relative to POR) and masses
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for (i=0; i<NUM; i++) {
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pm[i] = dRandReal()+0.1;
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q[i][0] = dRandReal()-0.5;
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q[i][1] = dRandReal()-0.5;
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q[i][2] = dRandReal()-0.5;
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}
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// adjust particle positions so centor of mass = POR
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computeMassParams (&m,q,pm);
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for (i=0; i<NUM; i++) {
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q[i][0] -= m.c[0];
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q[i][1] -= m.c[1];
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q[i][2] -= m.c[2];
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}
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if (world) dWorldDestroy (world);
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world = dWorldCreate();
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anchor_body = dBodyCreate (world);
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dBodySetPosition (anchor_body,pos1[0],pos1[1],pos1[2]);
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dMassSetBox (&anchor_m,1,SIDE,SIDE,SIDE);
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dMassAdjust (&anchor_m,0.1);
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dBodySetMass (anchor_body,&anchor_m);
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for (i=0; i<NUM; i++) {
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particle[i] = dBodyCreate (world);
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dBodySetPosition (particle[i],
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pos1[0]+q[i][0],pos1[1]+q[i][1],pos1[2]+q[i][2]);
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dMassSetBox (&m,1,SIDE,SIDE,SIDE);
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dMassAdjust (&m,pm[i]);
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dBodySetMass (particle[i],&m);
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}
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for (i=0; i < NUM; i++) {
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particle_joint[i] = dJointCreateBall (world,0);
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dJointAttach (particle_joint[i],anchor_body,particle[i]);
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const dReal *p = dBodyGetPosition (particle[i]);
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dJointSetBallAnchor (particle_joint[i],p[0],p[1],p[2]);
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}
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// make test_body with the same mass and inertia of the anchor_body plus
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// all the particles
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test_body = dBodyCreate (world);
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dBodySetPosition (test_body,pos2[0],pos2[1],pos2[2]);
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computeMassParams (&m,q,pm);
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m.mass += anchor_m.mass;
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for (i=0; i<12; i++) m.I[i] = m.I[i] + anchor_m.I[i];
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dBodySetMass (test_body,&m);
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// rotate the test and anchor bodies by a random amount
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dQuaternion qrot;
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for (i=0; i<4; i++) qrot[i] = dRandReal()-0.5;
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dNormalize4 (qrot);
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dBodySetQuaternion (anchor_body,qrot);
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dBodySetQuaternion (test_body,qrot);
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dMatrix3 R;
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dQtoR (qrot,R);
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for (i=0; i<NUM; i++) {
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dVector3 v;
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dMultiply0 (v,R,&q[i][0],3,3,1);
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dBodySetPosition (particle[i],pos1[0]+v[0],pos1[1]+v[1],pos1[2]+v[2]);
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}
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// set random torque
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for (i=0; i<3; i++) torque[i] = (dRandReal()-0.5) * 0.1;
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iteration=0;
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}
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// simulation loop
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static void simLoop (int pause)
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{
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if (!pause) {
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dBodyAddTorque (anchor_body,torque[0],torque[1],torque[2]);
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dBodyAddTorque (test_body,torque[0],torque[1],torque[2]);
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dWorldStep (world,0.03);
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iteration++;
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if (iteration >= 100) {
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// measure the difference between the anchor and test bodies
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const dReal *w1 = dBodyGetAngularVel (anchor_body);
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const dReal *w2 = dBodyGetAngularVel (test_body);
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const dReal *q1 = dBodyGetQuaternion (anchor_body);
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const dReal *q2 = dBodyGetQuaternion (test_body);
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dReal maxdiff = dMaxDifference (w1,w2,1,3);
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printf ("w-error = %.4e (%.2f,%.2f,%.2f) and (%.2f,%.2f,%.2f)\n",
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maxdiff,w1[0],w1[1],w1[2],w2[0],w2[1],w2[2]);
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maxdiff = dMaxDifference (q1,q2,1,4);
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printf ("q-error = %.4e\n",maxdiff);
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reset_test();
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}
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}
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dReal sides[3] = {SIDE,SIDE,SIDE};
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dReal sides2[3] = {6*SIDE,6*SIDE,6*SIDE};
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dReal sides3[3] = {3*SIDE,3*SIDE,3*SIDE};
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dsSetColor (1,1,1);
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dsDrawBox (dBodyGetPosition(anchor_body), dBodyGetRotation(anchor_body),
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sides3);
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dsSetColor (1,0,0);
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dsDrawBox (dBodyGetPosition(test_body), dBodyGetRotation(test_body), sides2);
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dsSetColor (1,1,0);
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for (int i=0; i<NUM; i++)
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dsDrawBox (dBodyGetPosition (particle[i]),
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dBodyGetRotation (particle[i]), sides);
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}
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int main (int argc, char **argv)
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{
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// setup pointers to drawstuff callback functions
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dsFunctions fn;
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fn.version = DS_VERSION;
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fn.start = &start;
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fn.step = &simLoop;
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fn.command = 0;
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fn.stop = 0;
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fn.path_to_textures = "../../drawstuff/textures";
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if(argc==2)
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{
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fn.path_to_textures = argv[1];
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}
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dInitODE();
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dRandSetSeed (time(0));
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reset_test();
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// run simulation
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dsSimulationLoop (argc,argv,352,288,&fn);
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dWorldDestroy (world);
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dCloseODE();
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return 0;
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}
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