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How can I use Bullet to affect the graphics

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Hello everyone!
I am sort of confused how to visualize this falling ball.
[source lang="cpp"]#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include <stdlib.h>
#include <iostream>
#include <btBulletDynamicsCommon.h>
static int slices = 16;
static int stacks = 16;
time_t last_update;
static float timestep = 1/60;
double fallY;
/* GLUT callback Handlers */
static void resize(int width, int height)
{
const float ar = (float) width / (float) height;
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-ar, ar, -1.0, 1.0, 2.0, 100.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity() ;
}
static void display(void)
{
const double t = glutGet(GLUT_ELAPSED_TIME) / 1000.0;
const double a = t*90.0;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3d(0.8,0.77,0.7);
glPushMatrix();
glTranslated(-2.4,1.2,-30);
glRotated(60,1,0,0);
time_t current_time = glutGet(GLUT_ELAPSED_TIME);
time_t since_update = current_time - last_update;
//if enough time has passed since the last redraw calculate physics
if(since_update>timestep)
{
dynamicsWorld->stepSimulation(timestep,10);
last_update = current_time;
}
btTransform trans;
fallRigidBody->getMotionState()->getWorldTransform(trans);
fallY = trans.getOrigin().getY();
glTranslated(0,0,fallY);
glutSolidSphere(1,slices,stacks);
glPopMatrix();
glutSwapBuffers();
}

static void key(unsigned char key, int x, int y)
{
switch (key)
{
case 27 :
exit(0);
break;
}
glutPostRedisplay();
}
static void idle(void)
{
glutPostRedisplay();
}
const GLfloat light_ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
const GLfloat light_diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_position[] = { 2.0f, 5.0f, 5.0f, 0.0f };
const GLfloat mat_ambient[] = { 0.7f, 0.7f, 0.7f, 1.0f };
const GLfloat mat_diffuse[] = { 0.8f, 0.8f, 0.8f, 1.0f };
const GLfloat mat_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat high_shininess[] = { 100.0f };
/* Program entry point */
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(640,480);
glutInitWindowPosition(10,10);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("GLUT Shapes");
glutReshapeFunc(resize);
glutDisplayFunc(display);
glutKeyboardFunc(key);
glutIdleFunc(idle);
glClearColor(1,1,1,1);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_LIGHT0);
glEnable(GL_NORMALIZE);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);

btBroadphaseInterface* broadphase = new btDbvtBroadphase();
btDefaultCollisionConfiguration* collisionConfiguration = new btDefaultCollisionConfiguration();
btCollisionDispatcher* dispatcher = new btCollisionDispatcher(collisionConfiguration);
btSequentialImpulseConstraintSolver* solver = new btSequentialImpulseConstraintSolver;
btDiscreteDynamicsWorld* dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher,broadphase,solver,collisionConfiguration);
dynamicsWorld->setGravity(btVector3(0,-10,0));

btCollisionShape* groundShape = new btStaticPlaneShape(btVector3(0,1,0),1);
btCollisionShape* fallShape = new btSphereShape(1);

btDefaultMotionState* groundMotionState = new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1),btVector3(0,-1,0)));
btRigidBody::btRigidBodyConstructionInfo
groundRigidBodyCI(0,groundMotionState,groundShape,btVector3(0,0,0));
btRigidBody* groundRigidBody = new btRigidBody(groundRigidBodyCI);
dynamicsWorld->addRigidBody(groundRigidBody);

btDefaultMotionState* fallMotionState =
new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1),btVector3(0,50,0)));
btScalar mass = 1;
btVector3 fallInertia(0,0,0);
fallShape->calculateLocalInertia(mass,fallInertia);
btRigidBody::btRigidBodyConstructionInfo fallRigidBodyCI(mass,fallMotionState,fallShape,fallInertia);
btRigidBody* fallRigidBody = new btRigidBody(fallRigidBodyCI);
dynamicsWorld->addRigidBody(fallRigidBody);

glutMainLoop();
return EXIT_SUCCESS;
}
[/source]
When I compile the code I got the following errors:
COMPUTER\C++\CppMyProjects\HW\main.cpp||In function 'void display()':|
COMPUTER\C++\CppMyProjects\HW\main.cpp|49|error: 'dynamicsWorld' was not declared in this scope|
COMPUTER\C++\CppMyProjects\HW\main.cpp|54|error: 'fallRigidBody' was not declared in this scope|
||=== Build finished: 2 errors, 0 warnings ===|

What should I do?
Please help!
Thank you so much!

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If you have to use GLUT, you'll almost inevitably have to use a few global variables :(

Unless I've missed something every time I've used it... (?)

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Can any give some modified code?
Many thanks!!!


Really?
If you don't know the difference between a local and a global variable, it's probably a good time to learn now.
http://lmgtfy.com/?q=global+vs+local+variable+c%2B%2B

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What should I do?


forget about opengl, bullet, glut and all that and learn C++.
That is what you should do.

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