creating a 3d cube and bouncing balls - c++

Question

I'm writing a program in OpenGL, I'm drawing a simple cube 3D and I want to add bouncing balls so that they bounce inside the walls of the cube, I tried to add a ball class and the following code:
GLfloat WHITE[] = {1, 1, 1};
GLfloat RED[] = {1, 0, 0};
GLfloat GREEN[] = {0, 1, 0};
GLfloat MAGENTA[] = {0, 0, 1};
class Ball {
double radius;
GLfloat* color;
double maximumHeight;
double x;
double y;
double z;
int direction;
public:
Ball(double r, GLfloat* c, double h, double x, double z):
radius(r), color(c), maximumHeight(h), direction(-1),
y(h), x(x), z(z) {
}
void update() {
y += direction * 0.05;
if (y > maximumHeight) {
y = maximumHeight; direction = -1;
} else if (y < radius) {
y = radius; direction = 1;
}
glPushMatrix();
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, color);
glTranslated(x, y, z);
glutSolidSphere(radius, 30, 30);
glPopMatrix();
}
};
Ball balls[] = {
Ball(0.5, GREEN, 7, 6, 1),
Ball(0.5, MAGENTA, 6, 3, 4),
Ball(0.5, WHITE, 5, 1, 7)
};
and in the display function I added this:
for (int i = 0; i < sizeof balls / sizeof(Ball); i++) {
balls[i].update();
}
This is my cube code:
void display();
void specialKeys();
double rotate_y=0;
double rotate_x=0;
void display(){
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glRotatef( rotate_x, 1.0, 0.0, 0.0 );
glRotatef( rotate_y, 0.0, 1.0, 0.0 );
glBegin(GL_POLYGON);
glColor3f( 1.0, 0.0, 0.0 ); glVertex3f( 0.5, -0.5, -0.5 ); // P1 is red
glColor3f( 0.0, 1.0, 0.0 ); glVertex3f( 0.5, 0.5, -0.5 ); // P2 is green
glColor3f( 0.0, 0.0, 1.0 ); glVertex3f( -0.5, 0.5, -0.5 ); // P3 is blue
glColor3f( 1.0, 0.0, 1.0 ); glVertex3f( -0.5, -0.5, -0.5 ); // P4 is purple
glEnd();
glBegin(GL_POLYGON);
glColor3f( 1.0, 1.0, 1.0 );
glVertex3f( 0.5, -0.5, 0.5 );
glVertex3f( 0.5, 0.5, 0.5 );
glVertex3f( -0.5, 0.5, 0.5 );
glVertex3f( -0.5, -0.5, 0.5 );
glEnd();
glBegin(GL_POLYGON);
glColor3f( 1.0, 0.0, 1.0 );
glVertex3f( 0.5, -0.5, -0.5 );
glVertex3f( 0.5, 0.5, -0.5 );
glVertex3f( 0.5, 0.5, 0.5 );
glVertex3f( 0.5, -0.5, 0.5 );
glEnd();
glBegin(GL_POLYGON);
glColor3f( 0.0, 1.0, 0.0 );
glVertex3f( -0.5, -0.5, 0.5 );
glVertex3f( -0.5, 0.5, 0.5 );
glVertex3f( -0.5, 0.5, -0.5 );
glVertex3f( -0.5, -0.5, -0.5 );
glEnd();
glBegin(GL_POLYGON);
glColor3f( 0.0, 0.0, 1.0 );
glVertex3f( 0.5, 0.5, 0.5 );
glVertex3f( 0.5, 0.5, -0.5 );
glVertex3f( -0.5, 0.5, -0.5 );
glVertex3f( -0.5, 0.5, 0.5 );
glEnd();*/
glBegin(GL_POLYGON);
glColor3f( 1.0, 0.0, 0.0 );
glVertex3f( 0.5, -0.5, -0.5 );
glVertex3f( 0.5, -0.5, 0.5 );
glVertex3f( -0.5, -0.5, 0.5 );
glVertex3f( -0.5, -0.5, -0.5 );
glEnd();
glFlush();
glutSwapBuffers();
}
void specialKeys( int key, int x, int y ) {
if (key == GLUT_KEY_RIGHT)
rotate_y += 5;
else if (key == GLUT_KEY_LEFT)
rotate_y -= 5;
else if (key == GLUT_KEY_UP)
rotate_x += 5;
else if (key == GLUT_KEY_DOWN)
rotate_x -= 5;
glutPostRedisplay();
}
int main(int argc, char* argv[]){
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow("Awesome Cube");
glEnable(GL_DEPTH_TEST);
glutDisplayFunc(display);
glutSpecialFunc(specialKeys);
glutMainLoop();
return 0;
}

Answer 1

GLfloat WHITE[] = {1, 1, 1};
...
Ball(0.5, WHITE, 5, 1, 7)
...
color(c)
....
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, color);
glMaterialfv():
GL_AMBIENT: params contains four integer or floating-point values
...
GL_DIFFUSE: params contains four integer or floating-point values
...
GL_AMBIENT_AND_DIFFUSE: Equivalent to calling glMaterial twice with the same parameter values, once with GL_AMBIENT and once with GL_DIFFUSE.
EDIT:
#include <GL/glut.h>
// http://eigen.tuxfamily.org
#include <Eigen/Core>
using namespace Eigen;
struct PointMass
{
PointMass() : pos(0,0,0), vel(0,0,0) {}
PointMass( const Vector3f& pos )
: pos( pos )
, vel( 0, 0, 0 )
{}
void Integrate( float dt )
{
// "gravity" force vector
Vector3f g( 0, 0, -2 );
// semi-implicit euler
vel = vel + g * dt;
pos = pos + vel * dt;
// collision detection/response
if( pos.z() < 0 )
{
pos.z() = -pos.z();
vel.z() = -vel.z();
}
}
Vector3f pos;
Vector3f vel;
};
GLfloat WHITE[] = {1, 1, 1, 1};
GLfloat RED[] = {1, 0, 0, 1};
GLfloat GREEN[] = {0, 1, 0, 1};
GLfloat MAGENTA[] = {0, 0, 1, 1};
class Ball
{
double radius;
GLfloat* color;
PointMass pm;
public:
Ball(double r, GLfloat* c, const Vector3f& pos )
: radius(r)
, color(c)
, pm( pos )
{ }
void Integrate( float dt )
{
pm.Integrate( dt );
}
void Draw()
{
glPushMatrix();
glColor4fv( color );
glTranslatef( pm.pos.x(), pm.pos.y(), pm.pos.z() );
glutSolidSphere(radius, 30, 30);
glPopMatrix();
}
};
Ball balls[] =
{
Ball( 0.1, GREEN, Vector3f( 1, 1, 2 ) ),
Ball( 0.1, MAGENTA, Vector3f( -1, 1, 1 ) ),
Ball( 0.1, WHITE, Vector3f( 0, -1, 1.5 ) ),
};
double rotate_x = 55;
double rotate_z = 25;
void display()
{
static int last = glutGet(GLUT_ELAPSED_TIME);
int cur = glutGet(GLUT_ELAPSED_TIME);
float dt = ( cur - last ) / 1000.0f;
last = cur;
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
double w = glutGet( GLUT_WINDOW_WIDTH );
double h = glutGet( GLUT_WINDOW_HEIGHT );
gluPerspective( 60, w / h, 0.1, 100 );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glTranslatef( 0, 0, -5 );
glRotatef( -rotate_x, 1.0, 0.0, 0.0 );
glRotatef( -rotate_z, 0.0, 0.0, 1.0 );
// ground
glBegin(GL_QUADS);
glColor3f( 1.0, 0.0, 0.0 );
glVertex2f( -2, -2 );
glColor3f( 0.0, 1.0, 0.0 );
glVertex2f( 2, -2 );
glColor3f( 0.0, 0.0, 1.0 );
glVertex2f( 2, 2 );
glColor3f( 1.0, 0.0, 1.0 );
glVertex2f( -2, 2 );
glEnd();
for (int i = 0; i < sizeof balls / sizeof(Ball); i++)
{
balls[i].Integrate( dt );
balls[i].Draw();
}
glutSwapBuffers();
}
void specialKeys( int key, int x, int y )
{
if (key == GLUT_KEY_RIGHT)
rotate_z += 5;
if (key == GLUT_KEY_LEFT)
rotate_z -= 5;
if (key == GLUT_KEY_UP)
rotate_x += 5;
if (key == GLUT_KEY_DOWN)
rotate_x -= 5;
}
void timer( int extra )
{
// run display() every 16ms or so
glutTimerFunc( 16, timer, 0 );
glutPostRedisplay();
}
int main(int argc, char* argv[])
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow("Awesome Cube");
glEnable(GL_DEPTH_TEST);
glutDisplayFunc(display);
glutSpecialFunc(specialKeys);
glutTimerFunc( 0, timer, 0 );
glutMainLoop();
return 0;
}