glVertex3f( (x+1)*squareSize, 0.0, (z+1)*squareSize );
glVertex3f( (x+1)*squareSize, 0.0, z*squareSize );
glVertex3f( x*squareSize, 0.0, z*squareSize );
glVertex3f( (x+1)*squareSize, 0.0, (z+1)*squareSize );
glVertex3f( (x+1)*squareSize, 0.0, z*squareSize );
glVertex3f( x*squareSize, 0.0, z*squareSize );