[Steve]

(continued)

The only feature which will fail is the 'feature' (=face(s)) you are working on.

I have not found this to be the case. Often when attempting to edit existing drafts or tapers, especially on heavily drafted and tapered parts, such as with cast or molded parts, the system is simply unable to compute a solution. Often it is not the faces you are working with that are causing the problem, it is neighboring geometry that is affected. But the software provides no clue as to what or where the problem area is. Eventually you get an eye for complicated intersections of surfaces on the model and you figure out what you need to cut away from the model in order to edit it, but what a depressing way to model. Basically you get to delete faces until the geometry is simplified enough to make your intended change, and then you get to recreate what you deleted to get it back in its previous state.

Yes, sometimes you have to do this in a history-based system, also, but at least you know which ones to delete.

The fact that the software has got a history isn't the reason why the software can or cannot tell the user why a feature creation/modification fails.

The history tree is precisely how the software can tell the user what feature(s) have failed, and the lack of a history tree is precisely why boolean modelers have no clue as to what is failing - they only know there is a mathematical error in attempting to describe the geometry as a whole.

With a history-based modeler, you are more of a programmer than an engineer.

I agree with this, but see this as a benefit. It makes engineers think about and document the engineering requirements of the geometry, which is a good thing.

Steve