creating a grids of squares (2D) in opengl using c++ - c++

Question

I want to make a square (2D) by using several smaller squares(like a grid). I need to do this because I want to texture an image on the main square and divide the picture into several pixels(the said smaller squares).
Here's the program:-
int h=1,w=1;
int res=25;// res is the number of smaller squares I want
float hratio=h/res;
float wratio=w/res;
void Draw()
{
float x,y;
for(y=-.5;y<=h;y+=h/res)
{
for(x=-.5;x<=w;x+=w/res)
{
glColor3f(1,1,1);
glBegin(GL_QUADS);
glVertex3f(x,y+(h/res),0);
glVertex3f(x+(w/res),y+(h/res),0);
glVertex3f(x+(w/res),y,0);
glVertex3f(x,y,0);
glEnd();
}
}
glFlush();
glutPostRedisplay();
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
Draw();
glutSwapBuffers();
glutPostRedisplay();
}
int main(int iArgc, char** cppArgv)
{
glutInit(&iArgc, cppArgv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(600, 600);
glutInitWindowPosition(200, 200);
glutCreateWindow("PIXELS");
glEnable(GL_DEPTH_TEST);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
when I run this program, all I get is a black screen.

Answer 1

Try this display function:
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
//set viewport
glViewport(0, 0, screen.width, screen.height);
//set projection matrix using intrinsic camera params
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float aspect = screen.width*1.0/screen.height;
//gluPerspective is arbitrarily set, you will have to determine these values based
//on the intrinsic camera parameters
gluPerspective(60.0f, aspect, 0.1f, 100.0f);
//you will have to set modelview matrix using extrinsic camera params
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0, 0, 5, 0, 0, 0, 0, 1, 0);
glLoadIdentity();
glTranslatef(0.0, 0.0, -5.0);
Draw();
glutSwapBuffers(); // Swap the front and back frame buffers (double buffering)
gluPostRedisplay();
}
In your case screen.width is 600 and screen.height is 600.