Extrude a thin flat part, i.e., something sheet metal thin. Sketch on one of the thin edges. Make the sketch cross both of the sketch surface edges. Use select contour to pick the sections to extrude. See if the contour tool doesn't use the underlying face edges as well as the sketched edges.
Actually I tried it in 2004 and it worked there too. I just ran across it first in 2008. Most people probably don't run into it because they sketch on a face that completely encloses the sketch. However, my question still stands as to whether this is a legitimate feature. It would seem that any feature that changes a sketches topology base on the sketch plane boundaries would be a bad feature. In other words if you sketch on a plane based on the narrow face instead of the face itself the "feature" goes away.
TOP wrote in news:d0fca338-7025-4cd5-a5f5-ec06d33c06f1 @c58g2000hsc.googlegroups.com:
IIRC, this was added about the time of contour select or maybe one realease later. I remember reading about it on one of the "what's new" pdfs. The purpose is to enable rapid closing of a profile to the model edges without having to use convert entities on the edges or "close sketch to model". The nice part is that the contour automatically updates to most changes in the face's edges.
Whether or not this is legitimate depends on what you mean by legitimate. It does capture design intent, so long as your intent is to use the sketched entities and whatever the rest of that face is. If you don't want that, then sketch it explicitly, or explicitly select the remaining regions.
I think I understand what you're saying...? It's a question of weather or not the sketch feature has legitimate intent... cuz of the boundary assumptions used with the contour selection and/or what is is preserved/absorbed too maintain some intended boundary history after the parent face deletion?
What's different in the latest release options is the option to delete (now default) or preserve (old way) the child features....where in the past the child sketch and feature would be preserved (default),.. is this what your seeing?