207 lines
5.9 KiB
C++
207 lines
5.9 KiB
C++
/*************************************************************************
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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 the Coulomb friction approximation.
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a 10x10 array of boxes is made, each of which rests on the ground.
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a horizantal force is applied to each box to try and get it to slide.
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box[i][j] has a mass (i+1)*MASS and a force (j+1)*FORCE. by the Coloumb
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friction model, the box should only slide if the force is greater than MU
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times the contact normal force, i.e.
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f > MU * body_mass * GRAVITY
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(j+1)*FORCE > MU * (i+1)*MASS * GRAVITY
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(j+1) > (i+1) * (MU*MASS*GRAVITY/FORCE)
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(j+1) > (i+1) * k
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this should be independent of the number of contact points, as N contact
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points will each have 1/N'th the normal force but the pushing force will
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have to overcome N contacts. the constants are chosen so that k=1.
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thus you should see a triangle made of half the bodies in the array start to
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slide.
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*/
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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 LENGTH 0.2 // box length & width
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#define HEIGHT 0.05 // box height
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#define MASS 0.2 // mass of box[i][j] = (i+1) * MASS
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#define FORCE 0.05 // force applied to box[i][j] = (j+1) * FORCE
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#define MU 0.5 // the global mu to use
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#define GRAVITY 0.5 // the global gravity to use
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#define N1 10 // number of different forces to try
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#define N2 10 // number of different masses to try
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// dynamics and collision objects
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static dWorldID world;
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static dSpaceID space;
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static dBodyID body[N1][N2];
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static dJointGroupID contactgroup;
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static dGeomID ground;
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static dGeomID box[N1][N2];
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// this is called by dSpaceCollide when two objects in space are
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// potentially colliding.
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static void nearCallback (void *data, dGeomID o1, dGeomID o2)
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{
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int i;
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// only collide things with the ground
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int g1 = (o1 == ground);
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int g2 = (o2 == ground);
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if (!(g1 ^ g2)) return;
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dBodyID b1 = dGeomGetBody(o1);
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dBodyID b2 = dGeomGetBody(o2);
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dContact contact[3]; // up to 3 contacts per box
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for (i=0; i<3; i++) {
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contact[i].surface.mode = dContactSoftCFM | dContactApprox1;
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contact[i].surface.mu = MU;
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contact[i].surface.soft_cfm = 0.01;
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}
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if (int numc = dCollide (o1,o2,3,&contact[0].geom,sizeof(dContact))) {
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for (i=0; i<numc; i++) {
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dJointID c = dJointCreateContact (world,contactgroup,contact+i);
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dJointAttach (c,b1,b2);
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}
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}
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}
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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] = {1.7772,-0.7924,2.7600};
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static float hpr[3] = {90.0000,-54.0000,0.0000};
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dsSetViewpoint (xyz,hpr);
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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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int i;
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if (!pause) {
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// apply forces to all bodies
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for (i=0; i<N1; i++) {
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for (int j=0; j<N2; j++) {
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dBodyAddForce (body[i][j],FORCE*(i+1),0,0);
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}
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}
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dSpaceCollide (space,0,&nearCallback);
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dWorldStep (world,0.05);
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// remove all contact joints
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dJointGroupEmpty (contactgroup);
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}
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dsSetColor (1,0,1);
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dReal sides[3] = {LENGTH,LENGTH,HEIGHT};
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for (i=0; i<N1; i++) {
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for (int j=0; j<N2; j++) {
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dsDrawBox (dGeomGetPosition(box[i][j]),dGeomGetRotation(box[i][j]),
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sides);
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}
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}
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}
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int main (int argc, char **argv)
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{
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int i,j;
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dMass m;
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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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// create world
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dInitODE();
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world = dWorldCreate();
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space = dHashSpaceCreate (0);
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contactgroup = dJointGroupCreate (0);
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dWorldSetGravity (world,0,0,-GRAVITY);
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ground = dCreatePlane (space,0,0,1,0);
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// bodies
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for (i=0; i<N1; i++) {
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for (j=0; j<N2; j++) {
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body[i][j] = dBodyCreate (world);
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dMassSetBox (&m,1,LENGTH,LENGTH,HEIGHT);
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dMassAdjust (&m,MASS*(j+1));
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dBodySetMass (body[i][j],&m);
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dBodySetPosition (body[i][j],i*2*LENGTH,j*2*LENGTH,HEIGHT*0.5);
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box[i][j] = dCreateBox (space,LENGTH,LENGTH,HEIGHT);
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dGeomSetBody (box[i][j],body[i][j]);
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}
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}
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// run simulation
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dsSimulationLoop (argc,argv,352,288,&fn);
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dJointGroupDestroy (contactgroup);
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dSpaceDestroy (space);
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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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