In this short tutorial for which I created a video I will show how you can use ZBrush’s grouploops for extracting smooth shapes with hard edges for hardsurface design:
The technique I used here is masking a certain area of a polymesh / dynamesh, invert the mask and then use the Transpose / Move tool to extract a shape out of the selection holding don the shift key and dragging the mouse.
When you don’t use grouploops for the selected area the edges are rough and the shape could be not quite straight. When defining grouploops and selecting the inner part of the unmasked area, the extracting shape you will get is really smooth and, straight and you will get a hard edge at the start of the exracting.
It’s an effective technique I often use for hardsurface design with ZBrush. When watching the video refer to the comments and hints I added to understand the methods and tools I used.