I check the initial Zbrush brush active unit is based on vertex, you draw on the surface basically pull or push the vertex in or out. But I have a question now requiring brush to active on the faces,(imagine you drew on one side of a cube with lowest subdivision, and I want to drag the face on that side out of the cube) like you do extrude faces in Max or Maya. but you use brush to control the value.
I was wondering if any scripts or plug-ins would help to achieve this effects. 
it is easy, just do it in max or maya and then bring it in to zbrush, otherwise it is too much hussle 
the model is actually way bigger than the image I upload, so it’s quite frustrated to manually modify it in Max or Maya, plus I want have a randomness but controllable hight value on the extrude. Like if I wanna do a patten based on this Grid model.
Thanks
i see, well there is a great free plugin for max called greeble, you should definitely check it out 
as far as zbrush, I don’t think that there’s an easy way unless you apply a checker texture to this model, them mask by intensity and then pull out poly’s, but i’d go with greeble, way quicker and hussle-free
here’s an example of what this plugin does in the image below
[[attach=175699]1227553805_greeble.jpg[/attach]](javascript:zb_insimg(‘175699’,‘1227553805_greeble.jpg’,1,0))
Thanks for your help, Skarpunin, I am going to try greeble 