Block 1:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(0.5, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(0.5, 0.5); glVertex3f(10.0, 10.0, 0.0);
      glTexCoord2f(0.0, 0.5); glVertex3f(-10.0, 10.0, 0.0);
   glEnd();

Block 2:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 1.0); glVertex3f(10.0, 10.0, 0.0);
   glEnd();

Block 3:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 1.0); glVertex3f(0.0, 10.0, 0.0);
   glEnd();

Block 4:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(0.5, 1.0); glVertex3f(0.0, 10.0, 0.0);
   glEnd();

Block 5:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 1.0); glVertex3f(20.0, 0.0, 0.0);
      glTexCoord2f(0.0, 1.0); glVertex3f(-10.0, 10.0, 0.0);
   glEnd();

Block 6:
   glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(1.0, 0.5); glVertex3f(20.0, 0.0, 0.0);
      glTexCoord2f(0.5, 1.0); glVertex3f(0.0, 10.0, 0.0);
      glTexCoord2f(0.0, 1.0); glVertex3f(-10.0, 0.0, 0.0);
   glEnd();

Block 7:
   glBegin(GL_POLYGON);
      glTexCoord2f(-1.0, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(2.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(2.0, 2.0); glVertex3f(10.0, 10.0, 0.0);
      glTexCoord2f(-1.0, 2.0); glVertex3f(-10.0, 10.0, 0.0);
   glEnd();

Block 8:
   glBegin(GL_POLYGON);
      glTexCoord2f(-0.5, 0.0); glVertex3f(-10.0, -10.0, 0.0);
      glTexCoord2f(2.0, 0.0); glVertex3f(10.0, -10.0, 0.0);
      glTexCoord2f(2.0, 2.0); glVertex3f(10.0, 10.0, 0.0);
      glTexCoord2f(-0.5, 2.0); glVertex3f(-10.0, 10.0, 0.0);
   glEnd();