Black thumb: How to bring a CAD system to its knees

I open up Creo Parametric, and load up a part model.  Not too complex — some bosses, holes, and a bunch of blends.  I select a blend (or “round,” to use PTC parlance), then click and drag its resizing handle.  And wait.  And wait.  Eventually, after several seconds, the blend resizes.   I wait some more, and the blend resizes again.  Ad nauseum.

Why so slow?  Because Creo was recalculating the blend on the fly, as I was dragging.  Since the blend was in the middle of the feature tree, with a bunch of other dependent geometry, each time I moved the cursor, it had to do a very time consuming recalculation.  The right way of resizing the blend would have been to click on the blend radius text, and type in a new value.  Presto… the blend is resized exactly as I wished.  Alternatively, I could have used Creo’s flexible modeling tools, which would have recalculated the blend more quickly (though, when I tried to interactively drag the blend radius using flexible modeling, I still found the dynamic response to be unsatisfying.)

Is there a way to fix the problem I’ve described?  Yes.  Were I moving a boss across a surface that forced topological changes, Creo would have switched to a simplified representation of the boss, rather than recalculating it accurately on the fly.  So, Creo does know how to adjust it’s dynamic response depending on the needs of the situation.  It just doesn’t do it with blends.

The point of talking about this isn’t to beat up PTC. Other CAD vendors have similar problems. Creo is a very powerful product, and expert users can make it sing.  But put a user with a black thumb in front of it, and they’ll often do things that will bring it to its knees.

If PTC were building Creo expressly to satisfy expert users, the kind of experience I’ve just described wouldn’t be an issue. Expert users are smart enough not to do dumb things.  Yet, PTC is going to increasingly find that its products are used by normal folks (not Pro/E gurus), who are less likely to understand the program’s nuances, and who are less likely to be accepting of its quirkiness.  It’s important to get the little details right, so that all users, and not just the experts, can get the most out of their CAD programs.