Why is this quad not rendering? Or if it is why can't I see it?

Question

I am using Visual C++ and GLUT. Am I missing something such a normals? this is the exact code I am using. I tried to insert glNormal3f(0, 0, 1); before the vertex statements but this did not change anything. The glutSolidSphere renders just as I expect it to but not the quad.

#include "stdafx.h"
#include <stdlib.h>
#include <GL/glut.h>


float spin = 0.0f;
float zDir = 0;
GLfloat diffuseIntensity[] = {.75, .75, .75, 1};
GLfloat specularHue[] = {0, 0, .5f, 1};
GLfloat shininess[] = {5};


void moveCamera();
void checkKeys(int, int, int);
void setUpLighting();
void changeSize(int w, int h) {


    if (h == 0)
        h = 1;

    float ratio =  w * 1.0 / h;


    glMatrixMode(GL_PROJECTION);    
    glLoadIdentity();   
    glViewport(0, 0, w, h); 
    gluPerspective(45,ratio,1,1000);    
    glMatrixMode(GL_MODELVIEW);
}

void renderScene(void) {

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    moveCamera();
    glTranslatef(0, 0, zDir-5);
    glEnable(GL_COLOR_MATERIAL);
    glShadeModel(GL_FLAT);
    glMaterialfv(GL_FRONT, GL_SHININESS, shininess);
    glMaterialfv(GL_FRONT, GL_SPECULAR, specularHue);
    glPushMatrix();
    glRotatef(90, 1, 0, 0);
    glRotatef(spin, 0, 0, 1);
    glutSolidSphere(.5f, 24, 24);
    glPopMatrix();
    spin += .01f;
    if(spin > 360) spin -= 360;

    glBegin(GL_QUADS);
    glVertex3f(-10, 0, -10);
    glVertex3f(-10, 0, 10);
    glVertex3f(10, 0, 10);
    glVertex3f(10, 0, -10);
    glEnd();
    glutSwapBuffers();
    glutPostRedisplay();
}

int main(int argc, char **argv) {


    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(800,600);
    glutCreateWindow("Lighthouse3D - GLUT Tutorial");


    glutDisplayFunc(renderScene);
    glutReshapeFunc(changeSize);
    glutSpecialFunc(checkKeys);
    glEnable(GL_DEPTH_TEST);
    setUpLighting();

    glutMainLoop();

    return 1;
}
void moveCamera(){


    glTranslatef(0, 0, zDir);

}

void checkKeys(int key, int x, int y){
    switch(key){

    case GLUT_KEY_UP:
        zDir += .1f;
        glutPostRedisplay();
        break;

    case GLUT_KEY_DOWN:
        zDir += -.1f;
        glutPostRedisplay();
        break;

    case GLUT_KEY_END:
        exit(0);
    }
}

void setUpLighting(){
    GLfloat position0[] = {3, 1, 0, 1};
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glLightfv(GL_LIGHT0, GL_POSITION, position0);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseIntensity);
}

Answer 1

Give this a shot:

#include <GL/glut.h>

float zDir = 12;
void checkKeys(int key, int x, int y)
{
    switch(key)
    {
    case GLUT_KEY_UP:
        zDir += -.5f;
        glutPostRedisplay();
        break;

    case GLUT_KEY_DOWN:
        zDir += .5f;
        glutPostRedisplay();
        break;

    case GLUT_KEY_END:
        exit(0);
    }
}

float spin = 0;
void renderScene(void)
{
    glEnable(GL_DEPTH_TEST);

    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(45,w/h,0.1,100);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glTranslatef(0, 0, -zDir);

    // set up light
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    GLfloat diffuseIntensity[] = {.75, .75, .75, 1};
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseIntensity);

    // draw sphere at light position
    glDisable( GL_LIGHTING );
    glPushMatrix();
    // spin light position around the y axis
    glRotatef( -spin, 0, 1, 0 );
    GLfloat position0[] = {3,3,3, 1};
    glLightfv(GL_LIGHT0, GL_POSITION, position0);
    glTranslatef( position0[0], position0[1], position0[2] );
    glColor3ub(255,255,255);
    glutSolidSphere(0.1,8,8);
    glPopMatrix();
    glEnable( GL_LIGHTING );

    // draw sphere
    glEnable(GL_COLOR_MATERIAL);
    glShadeModel(GL_FLAT);
    GLfloat specularHue[] = {0, 0, .5f, 1};
    GLfloat shininess[] = {5};
    glMaterialfv(GL_FRONT, GL_SHININESS, shininess);
    glMaterialfv(GL_FRONT, GL_SPECULAR, specularHue);

    spin += .01f;
    if(spin > 360) spin -= 360;

    glPushMatrix();
    glRotatef(spin, 0, 1, 0);
    glutSolidSphere(2, 24, 24);
    glPopMatrix();

    // draw quad
    glColor3ub(255,0,0);
    glPushMatrix();
    glScalef( 3, 3, 3 );
    glBegin(GL_QUADS);
    glNormal3f( 0, 0, 1 );
    glVertex2f( -1, -1 );
    glVertex2f(  1, -1 );
    glVertex2f(  1,  1 );
    glVertex2f( -1,  1 );
    glEnd();
    glPopMatrix();

    glutSwapBuffers();

    glutPostRedisplay();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(800,600);
    glutCreateWindow("Lighthouse3D - GLUT Tutorial");

    glutDisplayFunc(renderScene);
    glutSpecialFunc(checkKeys);
    glutMainLoop();
    return 1;
}

Answer 2

The quad is rendered, but you don't see it because it is drawn very much like the surface of a table and your eyes are at the same level of the table. Because of this, the effect is like that of which nothing was drawn at all. That or you'll see a line.

Your rotation above, being wrapped in a PushMatrix/PopMatrix only works with the solid sphere.