Smoothing groups

Got a problem with smoothing the model… I want some places of model to look sharp, because when you use smoothing groups on these parts they become smoothed and the result isn’t what i wanted. Is it allowed to not attack smoothing groups to some parts of model, and if it’s not allowed, what happens if you do not attach them?

Uh, just don’t select the part you don’t want smoothed when you’re applying the smoothing group?

I know :slight_smile: I’m making model for HL2, but i don’t know what might happen if i smoothing group won’t be attached to the part of model. May it result in model stretching or something other problems?
P.S. Sorry for my bad english.