glBegin(GL_QUADS);
           glTexCoord2f(0,0); glVertex3f(i-1,0,j-1);
           glTexCoord2f(2,0); glVertex3f(i-1,0,j);
           glTexCoord2f(2,4); glVertex3f(i-1,2,j);
           glTexCoord2f(0,4); glVertex3f(i-1,2,j-1);
         glEnd;
         glBegin(GL_QUADS);
           glTexCoord2f(0,0); glVertex3f(i-1,0,j);
           glTexCoord2f(2,0); glVertex3f(i,0,j);
           glTexCoord2f(2,4); glVertex3f(i,2,j);
           glTexCoord2f(0,4); glVertex3f(i-1,2,j);
         glEnd;
         glBegin(GL_QUADS);
           glTexCoord2f(0,0); glVertex3f(i,0,j);
           glTexCoord2f(2,0); glVertex3f(i,0,j-1);
           glTexCoord2f(2,4); glVertex3f(i,2,j-1);
           glTexCoord2f(0,4); glVertex3f(i,2,j);
         glEnd;
         glBegin(GL_QUADS);
           glTexCoord2f(0,0); glVertex3f(i,0,j-1);
           glTexCoord2f(2,0); glVertex3f(i-1,0,j-1);
           glTexCoord2f(2,4); glVertex3f(i-1,2,j-1);
           glTexCoord2f(0,4); glVertex3f(i,2,j-1);
         glEnd;