#FOG: do depth dead?

damn! my fog's billboards can't cooperate with mr depth. i talk to mr foggy last night.

me: please do me a favor.
mr foggy: i would not cooperate with this depth guy? huh!
me: please la. i am begging you ...
mr foggy: this is all his fault la, not me. i am doing the best i can.
mr foggy: i am fog, so my billboards has to stay close la. but this depth guy can except it.
me: so what should i do?
mr foggy: i don't know, but sometimes i can sacrifice my principle la ... it is only for you la ..
me: how is that?
mr foggy: to do so, you have to leave a space between my billboards.
me: that's it?
mr foggy: yeah, but you'll will see a weird fog. not a fog actually.
me: hah! mmm, damn! i am stuck! oklah, i am going to bed. *wish to dream how to solve this*

if i don't use this depth guy or technically known as gl_depth_test, all the objects, the billboards will be draw in one straight line. because there is no depth. if i use this depth guy, my fog look jaggy. and sometimes i wonder, why don't the quads/billboards blend it's texture. why lah? adakah ini salah opengl? or the setting is not correct kah? look at the pic lah for more details views.