ODE (Open Dynamic Engine) 是一个免费的具有工业品质的刚体动力学的库，一款优秀的开源物理引擎。它能很好地仿真现实环境中的可移动物体，而且它有内建的碰撞检测系统。

        最近从网上看到了ODE，不禁有一种跃跃欲试的冲动，于是这两天就小试了一下。虽然ODE这个库已经使用了十几年了，但是资料还是比较少，中文的更是寥寥可数，只有几篇官网教程的翻译，也只有前几章的，不是很全。貌似这种日本做的东西，文档做的都不是很好呀。以下是几篇教程的链接：

       ODE文档的部分翻译： 

                                           

       ODE 教程：

                          

                                            

            没办法，就开始看官方源码中的demo，今天花了一下午时间看了buggy的例程，对照着在线手册了解了程序中的API，简单做了一下中文注释。

       

/************************************************************************* *                                                                       * * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith.       * * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          * *                                                                       * * This library is free software; you can redistribute it and/or         * * modify it under the terms of EITHER:                                  * *   (1) The GNU Lesser General Public License as published by the Free  * *       Software Foundation; either version 2.1 of the License, or (at  * *       your option) any later version. The text of the GNU Lesser      * *       General Public License is included with this library in the     * *       file LICENSE.TXT.                                               * *   (2) The BSD-style license that is included with this library in     * *       the file LICENSE-BSD.TXT.                                       * *                                                                       * * This library is distributed in the hope that it will be useful,       * * but WITHOUT ANY WARRANTY; without even the implied warranty of        * * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    * * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     * *                                                                       * *************************************************************************//*   buggy with suspension.   this also shows you how to use geom groups.*/#define  dSINGLE    //定义为单精度#include 
    
     #include 
     
      #define DRAWSTUFF_TEXTURE_PATH "textures"   //纹理文件的路径// select correct drawing functions#ifdef dDOUBLE#define dsDrawBox dsDrawBoxD#define dsDrawSphere dsDrawSphereD#define dsDrawCylinder dsDrawCylinderD#define dsDrawCapsule dsDrawCapsuleD#endif// some constants#define LENGTH 0.7	// 车壳长度#define WIDTH 0.5	// 车壳宽度#define HEIGHT 0.2	// 车壳高度#define RADIUS 0.18	// 轮子半径#define STARTZ 0.5	// 开始车壳的位置#define CMASS 1		// 车壳的质量#define WMASS 0.2	// 轮子的质量// dynamics and collision objects (chassis, 3 wheels, environment)static dWorldID world;      //动力学计算使用的worldstatic dSpaceID space;      //检测碰撞使用的spacestatic dBodyID body[4];     //设置车体的ID(三个轮子，一个车体)static dJointID joint[3];	// joint[0]是前轮static dJointGroupID contactgroup;static dGeomID ground;      //大地static dSpaceID car_space;static dGeomID box[1];       //车体geom的IDstatic dGeomID sphere[3];    //车轮geom的IDstatic dGeomID ground_box;   //障碍物geom的ID// things that the user controlsstatic dReal speed=0,steer=0;	// 用户命令// 碰撞检测的callback函数static void nearCallback (void *data, dGeomID o1, dGeomID o2){  int i,n;  // 选择碰撞检测中的2个中的一个作为标志；  // 如果有一个碰撞物为ground或者障碍物则把标志位g1\g2置为1  int g1 = (o1 == ground || o1 == ground_box);  int g2 = (o2 == ground || o2 == ground_box);  if (!(g1 ^ g2)) return;  const int N = 10;    //接触点的上限是10个  dContact contact[N];  n = dCollide (o1,o2,N,&contact[0].geom,sizeof(dContact));   //n是碰撞的次数  if (n > 0) {    for (i=0; i
      
        0.1) v = 0.1;    if (v < -0.1) v = -0.1;    v *= 10.0;    dJointSetHinge2Param (joint[0],dParamVel,v);    dJointSetHinge2Param (joint[0],dParamFMax,0.2);    dJointSetHinge2Param (joint[0],dParamLoStop,-0.75);    //最小停止角度    dJointSetHinge2Param (joint[0],dParamHiStop,0.75);     //最大停止角度    dJointSetHinge2Param (joint[0],dParamFudgeFactor,0.1);  //防止启动跳动    dSpaceCollide (space,0,&nearCallback);   //碰撞检测，最初写入的值    dWorldStep (world,0.05);                 //决定simulation的stepsize    // remove all contact joints    dJointGroupEmpty (contactgroup);          //将contactgroup置空  }  //DrawStuff绘制  dsSetColor (0,1,1);       //颜色切换  dsSetTexture (DS_WOOD);   //纹理切换  dReal sides[3] = {LENGTH,WIDTH,HEIGHT};   //车壳的尺寸  dsDrawBox (dBodyGetPosition(body[0]),dBodyGetRotation(body[0]),sides);   //绘制车壳  dsSetColor (1,1,1);  for (i=1; i<=3; i++) dsDrawCylinder (dBodyGetPosition(body[i]),				       dBodyGetRotation(body[i]),0.02f,RADIUS);    //绘制车轮  dVector3 ss;  dGeomBoxGetLengths (ground_box,ss);  dsDrawBox (dGeomGetPosition(ground_box),dGeomGetRotation(ground_box),ss);   //绘制障碍}int main (int argc, char **argv){  int i;  dMass m;  // setup pointers to drawstuff callback functions  dsFunctions fn;           // drawstuff结构体  fn.version = DS_VERSION;  // drawstuff的版本  fn.start = &start;        // 仿真的前处理函数  fn.step = &simLoop;       // 仿真的每一步被调用的函数  fn.command = &command;    // 键盘输入  fn.stop = 0;              // 没有函数，因此设定为NULL指针  fn.path_to_textures = DRAWSTUFF_TEXTURE_PATH;  // 纹理文件的路径  // create world  dInitODE2(0);                    //初始化ODE环境  world = dWorldCreate();          //创建世界  space = dHashSpaceCreate (0);    //创建碰撞检测用space，返回它的ID。  contactgroup = dJointGroupCreate (0);   //生成jointGroup  dWorldSetGravity (world,0,0,-0.5);      //重力加速度  ground = dCreatePlane (space,0,0,1,0);  //创建一个ground  // 创建车体  body[0] = dBodyCreate (world);  dBodySetPosition (body[0],0,0,STARTZ);    //设置初始位置  dMassSetBox (&m,1,LENGTH,WIDTH,HEIGHT);  dMassAdjust (&m,CMASS);  dBodySetMass (body[0],&m);                   //设置质量  box[0] = dCreateBox (0,LENGTH,WIDTH,HEIGHT); //生成车体的geom  dGeomSetBody (box[0],body[0]);               //设置车体中的geom，给物体的两个属性形状geom和刚体body添加关联。  // wheel bodies  for (i=1; i<=3; i++) {    body[i] = dBodyCreate (world);          //创建车轮的body    dQuaternion q;    dQFromAxisAndAngle (q,1,0,0,M_PI*0.5);  //计算车轮的旋转角度    dBodySetQuaternion (body[i],q);         //设置车轮的旋转角度    dMassSetSphere (&m,1,RADIUS);    dMassAdjust (&m,WMASS);    dBodySetMass (body[i],&m);             //设置质量    sphere[i-1] = dCreateSphere (0,RADIUS);    dGeomSetBody (sphere[i-1],body[i]);    //设置geom  }  dBodySetPosition (body[1],0.5*LENGTH,0,STARTZ-HEIGHT*0.5);    //设置初始位置  dBodySetPosition (body[2],-0.5*LENGTH, WIDTH*0.5,STARTZ-HEIGHT*0.5);  dBodySetPosition (body[3],-0.5*LENGTH,-WIDTH*0.5,STARTZ-HEIGHT*0.5);  // front and back wheel hinges  for (i=0; i<3; i++) {    joint[i] = dJointCreateHinge2 (world,0);         //创建joint    dJointAttach (joint[i],body[0],body[i+1]);       //设置joint的连接体    const dReal *a = dBodyGetPosition (body[i+1]);   //获取位置    dJointSetHinge2Anchor (joint[i],a[0],a[1],a[2]); //设置joint的位置    dJointSetHinge2Axis1 (joint[i],0,0,1);           //设置旋转轴    dJointSetHinge2Axis2 (joint[i],0,1,0);  }  // 设置joint的悬挂参数  // 如果不需要悬挂可以将参数设置为0  for (i=0; i<3; i++) {                                 dJointSetHinge2Param (joint[i],dParamSuspensionERP,0.4);    dJointSetHinge2Param (joint[i],dParamSuspensionCFM,0.8);  }  // 固定后面两个轮子  for (i=1; i<3; i++) {    // set stops to make sure wheels always stay in alignment    dJointSetHinge2Param (joint[i],dParamLoStop,0);    dJointSetHinge2Param (joint[i],dParamHiStop,0);  }  // 创建car的space，并且包含在总的space中  car_space = dSimpleSpaceCreate (space);  dSpaceSetCleanup (car_space,0);  dSpaceAdd (car_space,box[0]);  dSpaceAdd (car_space,sphere[0]);  dSpaceAdd (car_space,sphere[1]);  dSpaceAdd (car_space,sphere[2]);  // 设置障碍  ground_box = dCreateBox (space,2,1.5,1);  dMatrix3 R;  dRFromAxisAndAngle (R,0,1,0,-0.15);  dGeomSetPosition (ground_box,2,0,-0.34);  dGeomSetRotation (ground_box,R);  // run simulation  dsSimulationLoop (argc,argv,352,288,&fn);  dGeomDestroy (box[0]);  dGeomDestroy (sphere[0]);  dGeomDestroy (sphere[1]);  dGeomDestroy (sphere[2]);  dJointGroupDestroy (contactgroup);  dSpaceDestroy (space);  dWorldDestroy (world);  dCloseODE();  return 0;}
      
     
    

               运行效果：            

               程序中比较难理解的是一些参数的设置和API的使用。

         当发生碰撞时，调用回调函数nearCallback，其中需要设置一些碰撞点的参数，具体的参数可以参考用户手册中的说明：

        joint的配置中也有一些参数的设置：

 

        以上均参考在线文档：

        API手册：

            用户手册：