4. 3D Graphics

Basic geometries: sphere, box, cylinder, capsule and rays

This is the 4th ODE tutorial.

The ODE (Open Dynamics Engine) Learn about the 3D graphics. ODE will perform a demonstration of the moving cloud and the ground texture improve the quality of the simulation is a good appearance. This, ODE with occurrences omitted to be done drawstuff 3D graphics library.ODE drawstuff just a demo program in a position for viewing features are only so simple, even drawing a polygon is insufficient in late drawstuff so the other might use the library. In addition to using Windows to Linux, but if a candidate Ogre3D irrlicht and think about.

drawstuff called the OpenGL 3D graphics library is written using the library is very simple.It’s easy to learn OpenGL is a perfect fit. In addition, drawstuff on the API (function) begins with a lowercase ds, ODE on the API begins with a lowercase d.

Using drawstuff

• To include the header file

#include <drawstuff/drawstuff.h>

• Settings

In order to use drawstuff dsFunctions bottom of the structure must be set for each member.

// define of dsFunctions structure
typedef struct dsFunctions {
  int version;  /* set DS_VERSION */ 　
  void (*start)(); 	/* start function before simulation */
  void (*step) (int pause);	/* step function  */
  void (*command) (int cmd); /* command function for keyboard  */
  void (*stop)();	/* stop function after simulation */
  const char *path_to_textures;	/* a path to the texture */
} dsFunctions;

• • Version: DS_VERSION to assign
    • fn.version = DS_VERSION
  • Pre-processing functions: the simulation will be called before the start of the loop.Here, the eye of the camera viewpoint and the general set.
    • fn.start = &start;
    • Viewpoint of the camera, eyes
      dsSetViewpoint (point of view, the eye);
  • Loop simulation function: in each loop of the Simulation will be called each time. The function to compute dynamics, collision detection process of drawing write and compute. Drawing on a sample programs treatment only in writing.
    • fn.step = &simLoop;
    • Drawing API to write about
  • Key processing function: the key is pressed at a time is called. If you do not need to NULL (NURUPOINTA) assignment. 0 NULL pointer was a special point to address.
    • fn.command = &command;
  • Post-processing functions: the simulation is called after the loop. If you do not need to NULL (NURUPOINTA) assignment.
    • fn.stop = &stop;
  • Texture path
    • fn.path_to_textures = “path”;
• Real line
  • The following API calls to be drawn only once. While inside the loop.

    dsSimulationLoop (argc, argv, witdh, height, & fn);

    • argc, argv: main function arguments
    • width: The width of the window
    • height: The height of the window
    • fn: dsFunctions DOROSUTAFFU variable structure

Sample program

/* ODE tutorial  by Kosei Demura */
/* Lesson 4 3D Graphics          */
#include "ode/ode.h"
#include "drawstuff/drawstuff.h"
#ifdef _MSC_VER
#pragma warning(disable:4244 4305)  // Stop VC++ warnings
#endif
#ifdef dDOUBLE
#define dsDrawBox  dsDrawBoxD
#define dsDrawSphere   dsDrawSphereD
#define dsDrawCylinder dsDrawCylinderD
#define dsDrawCapsule  dsDrawCapsuleD
#define dsDrawLine     dsDrawLineD
#endif

#define DENSITY (5.0)

struct MyObject {
  dBodyID body;		// a rigid body
};

dReal radius = 0.25; // radius
dReal length = 1.0;  // length
dReal sides[3] = {0.5,0.5,1.0}; // length of edges
static dWorldID world;  // a dynamic world
static MyObject sphere, box, capsule, cylinder; // objects

// start simulation
static void start()
{
  static float xyz[3] = {5,3,0.5};    // view point [m]
  static float hpr[3] = {-180, 0, 0}; // view direction[°]
  dsSetViewpoint (xyz,hpr);           // set a view point and direction
}

// Simulation loop
static void simLoop (int pause)
{
  const dReal *pos1,*R1,*pos2,*R2,*pos3,*R3;    //　draw a sphere
  dsSetColor(1,0,0);      // set red color
  dsSetSphereQuality(3);  // set quality of spere. 3 is pretty good
  pos1 = dBodyGetPosition(sphere.body); // get a position
  R1   = dBodyGetRotation(sphere.body); // get an orientation
  dsDrawSphere(pos1,R1,radius);         // draw a sphere

  // draw a cylinder
  dsSetColorAlpha (0,1,0,1);
  pos2 = dBodyGetPosition(cylinder.body);
  R2   = dBodyGetRotation(cylinder.body);
  dsDrawCylinder(pos2,R2,length,radius);
  // draw an capsule   dsSetColorAlpha (1,1,1,1);
  pos2 = dBodyGetPosition(capsule.body);
  R2   = dBodyGetRotation(capsule.body);
  dsDrawCapsule(pos2,R2,length,radius);

  // draw a box
  dsSetColorAlpha (0,0,1,1);
  pos3 = dBodyGetPosition(box.body);
  R3   = dBodyGetRotation(box.body);
  dsDrawBox(pos3,R3,sides);           // draw a line
  dReal posA[3] = {0, 5, 0},  posB[3]={0, 5, 1.9};
  dsDrawLine(posA,posB);
}

int main (int argc, char **argv)
{
  // set drawstuff
  dsFunctions fn;
  fn.version = DS_VERSION;
  fn.start   = &start;
  fn.step    = &simLoop;
  fn.command = NULL;
  fn.stop    = NULL;
  fn.path_to_textures = "../../drawstuff/textures";

  dInitODE();              // Initialize ODE
  world = dWorldCreate();  // Create a world

  dMass m;                 // mass parameter
  dMassSetZero (&m);  //set mass parameter to zero

  //　sphere
  sphere.body = dBodyCreate (world);     //  create a body
  dReal radius = 0.5;       // radius [m]
  dMassSetSphere (&m,DENSITY,radius); // Calcurate mass parameter
  dBodySetMass (sphere.body,&m);  // Set mass parameter to the body
  dBodySetPosition (sphere.body,0,1, 1); // Set a position

  //　Box
  box.body = dBodyCreate (world);
  dMassSetBox (&m,DENSITY,sides[0],sides[1],sides[2]);
  dBodySetMass (box.body,&m);
  dBodySetPosition (box.body,0,2,1);

  // Capsule
  capsule.body = dBodyCreate (world);
  dMassSetCapsule(&m,DENSITY,3,radius,length);
  dBodySetMass (capsule.body,&m);
  dBodySetPosition (capsule.body,0,4,1);

  // Cylinder
  cylinder.body = dBodyCreate (world);
  dMassSetCylinder(&m,DENSITY,3,radius,length);
  dBodySetMass (cylinder.body,&m);
  dBodySetPosition (cylinder.body,0,3,1);

  // Simulation loop
  dsSimulationLoop (argc,argv,960,480,&fn);

 dWorldDestroy (world); // destroy the world
  dCloseODE();              // close ODE
  return 0;
}

Download

• Sample4 (sample4-110105.zip) can be downloaded from here.

That’s all. Next time, let’s learn a body and a geometry.