Quote - where i am at

What is the best technique for adding things like joint lines, and hatches. And what about screens. And fender tread plate patterns?

Every time you post that, you make me want to model a tank now.  :)

In my opinion, for the hatches, it's probably best to cut them in and model them.  The joint lines, you could probably get away with bump mapping them.  If that doesn't give you enough detail, you'll want to cut them in.  For the tread plate patterns (diamond plating), you should be able to get a good enough effect from a bump map. 

Were you able to get your blue print lined up close enough?

Reddog9
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