Please help - object lines are not stright

I did some 3d city scene with buildings ,I did perspective projection ,but the side lines are not stright(the coordinates are ok).
It looks like every 20-30 pixels up the x coordinate is changing + or - 1-2 pixels.

I think what you are getting is called “aliasing”. Try turning on anti-aliasing (might say FSAA in your drivers).

Just a guess