What is a "brep"?

(David Cockey) #1

What is a “brep” as used in discussions on this forum?

DIG : Rhino models/scene setup for Architectural Illustrations
Centroid for line or polyline
(Steve Baer) #2

Here’s a wikipedia article that sums up the term much better than I could do

(Pascal Golay) #3

Hi David- I’d read Steve’s link, but in the context of Rhino, this might help - - Rhino has different ways of representing shapes; things that show up in ‘What’ command report as surfaces or Polysurfaces are BReps, but things that are listed as Extrusions are not, though they are easily, often, and for the most part transparently converted to Breps when working with them in Rhino. (e.g. FilletEdge on an extrusion object,- Box for example- and it becomes a polysurface — a Brep.

At any rate, Extrusions are new in V5 and can cause some confusion where they do not behave exactly like Breps- that is probably where you will encounter the most discussion here. e.g. Make a box, turn on points- this works because the box is an extrusion object defined by a shape curve and an extrusion direction and has a special extrusion style grips, or points. But if you fillet an edge of this box, and then turn control points on – you cannot, the shape is now defined by the faces on all sides, edges and join information and so on - it is a polysurface and a and you do not get to turn on control points for these. (ignoring SolidPtOn for now).

More info on extrusions here:

Dunno if that helps or muddies- hopefully I have not told any outright lies.