OpenGL _ Front objects are covered with Back objects. so can't see it

The problem is, 'Objects on the table is covered with table board, so can't see it.' ( I using openGL 3.7 beta. Files that I installed is : http://ihoo1836.dothome.co.kr/opengl_vs2010+glutdlls37beta.zip ) All Codes are following. ``` #include<glut.h> #include<stdio.h> #include<stdlib.h> #include<time.h> float TableX = 5.0; //Table's X size float TableY = 8.0; //Table's Y size float TableHeight = 2.0;//Table's Height int width=400, height=400; //Window Size int ViewX = width/2; //for Change Viewpoint by Mouse position int ViewY = height/2; int ViewZ = 9; GLUquadricObj* cyl; void InitLight( ){ glEnable(GL_DEPTH_TEST); //for opaque glEnable(GL_NORMALIZE); //normalize glEnable(GL_SMOOTH); //for smooth color glEnable(GL_LIGHTING); //light setting glDepthMask(GL_TRUE); GLfloat ambientLight[] = {0.3f, 0.3f, 0.3f, 1.0f}; GLfloat diffuseLight[] = {0.7f, 0.7f, 0.7f, 1.0f}; GLfloat specular[] = {1.0f, 1.0f, 1.0f, 1.0f}; GLfloat specref[] = {1.0f, 1.0f, 1.0f, 1.0f}; GLfloat position[]={400.0, 300.0, -700.0, 1.0}; glLightfv(GL_LIGHT0, GL_AMBIENT, ambientLight); glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight); glLightfv(GL_LIGHT0, GL_SPECULAR, specular); glLightfv(GL_LIGHT0, GL_POSITION, position); glEnable(GL_LIGHT0); glEnable(GL_COLOR_MATERIAL); glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE); glMateriali(GL_FRONT, GL_SHININESS, 128); } //Get Mouse Position to Change ViewPoint void MyMouseMove(int button, int state, GLint X, GLint Y) { //Get Mouse Position X, Y ViewX = X; ViewY = Y; glutPostRedisplay(); } //Get Mouse Position to Change ViewPoint void MyMotion(GLint X, GLint Y) { //Get Mouse Position X, Y ViewX = X; ViewY = Y; glutPostRedisplay(); } //Draw Table void DrawTable(){ glPushMatrix(); glTranslatef(0.0,0.0,1.0); glColor3f(0.5, 0.25, 0.0); cyl = gluNewQuadric(); glRotatef(-90,1.0,0.0,0.0); gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 1 glPushMatrix(); cyl = gluNewQuadric(); glTranslatef(TableX,0.0,0.0); gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 2 glPushMatrix(); cyl = gluNewQuadric(); glTranslatef(0.0, TableY, 0.0); gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 3 glPushMatrix(); cyl = gluNewQuadric(); glTranslatef(-TableX,0.0,0.0); gluCylinder(cyl, 0.2, 0.2, TableHeight, 10, 20); //Leg of Table 4 glPushMatrix(); glTranslatef(TableX/2.0, -TableY/2, TableHeight); glScalef(TableX+0.5, TableY+0.5, 0.5); glutSolidCube(1); //Board of Table glPopMatrix(); glPushMatrix(); //triangular1 (Beside of Net) glTranslatef(0, -TableY/2, TableHeight); glBegin(GL_TRIANGLES); glVertex3f(TableY/16.0, 0, TableY/8.0);//1 glVertex3f(0, TableY/8.0, 0); glVertex3f(0, -TableY/8.0, 0); glVertex3f(TableY/16.0, 0, TableY/8.0);//2 glVertex3f(0, -TableY/8.0, 0); glVertex3f(TableY/16.0, -TableY/8.0, 0); glVertex3f(TableY/16.0, 0, TableY/8.0);//3 glVertex3f(TableY/16.0, -TableY/8.0, 0); glVertex3f(TableY/16.0, TableY/8.0, 0); glVertex3f(TableY/16.0, 0, TableY/8.0);//4 glVertex3f(TableY/16.0, TableY/8.0, 0); glVertex3f(0, TableY/8.0, 0); glEnd(); glPushMatrix(); //triangular2 (Beside of Net) glTranslatef(TableX - TableY/8.0, 0 , 0); glBegin(GL_TRIANGLES); glColor3f(1.0, 0.0, 0.0); glVertex3f(TableY/16.0, 0, TableY/8.0);//1 glColor3f(0.0, 1.0, 0.0); glVertex3f(TableY/16.0, TableY/8.0, 0); glColor3f(0.0, 0.0, 1.0); glVertex3f(TableY/16.0, -TableY/8.0, 0); glColor3f(1.0, 0.0, 0.0); glVertex3f(TableY/16.0, 0, TableY/8.0);//2 glColor3f(0.0, 1.0, 0.0); glVertex3f(TableY/16.0, -TableY/8.0, 0); glColor3f(0.0, 0.0, 1.0); glVertex3f(TableY/8.0, -TableY/8.0, 0); glColor3f(1.0, 0.0, 0.0); glVertex3f(TableY/16.0, 0, TableY/8.0);//3 glColor3f(0.0, 1.0, 0.0); glVertex3f(TableY/8.0, -TableY/8.0, 0); glColor3f(0.0, 0.0, 1.0); glVertex3f(TableY/8.0, TableY/8.0, 0); glColor3f(1.0, 0.0, 0.0); glVertex3f(TableY/16.0, 0, TableY/8.0);//4 glColor3f(0.0, 1.0, 0.0); glVertex3f(TableY/8.0, TableY/8.0, 0); glColor3f(0.0, 0.0, 1.0); glVertex3f(TableY/16.0, TableY/8.0, 0); glEnd(); glPopMatrix(); glPushMatrix(); //Net glBegin(GL_POLYGON); glColor3f(1.0, 1.0, 1.0); glVertex3f(TableY/16.0, 0.0, TableY/8.0); glVertex3f((TableX - TableY/16.0), 0, TableY/8.0); glVertex3f((TableX - TableY/16.0), 0, 0); glVertex3f(TableY/16.0, 0.0, 0.0); glEnd(); glPopMatrix(); glPopMatrix(); glPopMatrix(); glPopMatrix(); glPopMatrix(); glPopMatrix(); } //Display Callback Function void MyDisplay( ){ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity( ); gluPerspective(60.0, (GLfloat)width/height, 0.0, 10.0); //Change Viewpoint by Mouse Position gluLookAt((float)(ViewX - width/2)/width*20 + 2.5, (float)(height/2 - ViewY)/height*20 + 2.5, ViewZ, TableX/2, TableY/2, TableHeight, 0.0, 1.0, 0.0); printf("eyex = %f , eyey = %f , eyez = %f \n",(float)(ViewX - width/2.0)/width*10, (float)(height/2 - ViewY)/height*10, (float)ViewZ); DrawTable(); //Draw Table glutSwapBuffers(); //for 'Double Buffering' } //for Reshape Window void MyReshape (int w, int h){ width = w; height = h; printf("width = %d, height = %d \n", width, height); glViewport (0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode (GL_PROJECTION); glLoadIdentity( ); glOrtho (-1.0, 1.0, -1.0, 1.0, -1.0, 1.0); } //Main Function int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE); glutInitWindowSize(width, height); glutInitWindowPosition(200, 200); glutCreateWindow("OpenGL Sample Drawing"); glClearColor(0.4, 0.4, 0.4, 1.0); InitLight(); //set Light Setting glutDisplayFunc(MyDisplay); glutMouseFunc(MyMouseMove); //get Mouse Position, to Change Viewpoint glutMotionFunc(MyMotion); //get Mouse Position, to Change Viewpoint glutReshapeFunc(MyReshape); glutMainLoop( ); } ```