thanx a lot for your information.i found a good tut but there is some thing i dont understand.
here is the tut:
https://www.carbodydesign.com/goto.php?id=27
-i dont know how to create a simpleinfo node
-and when i create 3 ramp texture, i dont see their
2d_placement nodes.

for now i dont understand these two things but... i will surely come back to ask some other question.