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Old 05-02-2007, 02:37 PM
Steve Steve is offline
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Join Date: Mar 2003
Location: Alabama
Posts: 309
Re: OneSpace vs. SolidWorks

Hi Steve,

In my opinion, once you have used an "intelligent" modeler you will never be satisfied with a "dumb" modeler.

I started using CAD back before solid modeling was commonly available, and cut my teeth on solids using Unigraphics somewhere around V8 or V9. At the time, UG was a Boolean modeler very much like CoCreate is today - all geometry manipulation was done by moving or deleting faces, or gluing on or hacking away parts of the model via Boolean operations. There was no real way to embed intelligence into the model.

Of course it was not long and solid modelers evolved to allow you to create relationships between geometric entities. This, in my opinion, is one of the main features of CAD - the ability to define relationships between geometric entities so that the operator (and future operators) does not have to remember them and manage them manually.

Once you have used software that has that kind of ability, it is very frustrating to go back to software that does not have that ability. For example, let's suppose you have a cylinder of 1 inch in diameter. In CoCreate, if you taper that cylinder, the system forgets that there ever was a cylinder there - it now sees the body as a conical body. So if you want to change the underlying diameter, you can't. You must either delete the taper, change the diameter, and then re-apply the taper, or you must do trigonometry to figure out how far to offset the conical surface to achieve the new desired base diameter. The lack of history means the lack of ability to control the geometry by theoretical foundations.

Moreover, the problem with the non-history-based approach to geometry manipulation is when the model fails to regenerate (and this happens with all software if you attempt to modify the model in such a way that the system is unable to compute a solution) you have no idea what is causing the failure. When a history based model fails, the system tells you precisely what features are failing and to some extent guides you in what you need to do to fix the problem. When a Cocreate model fails, basically you are left with a simple error like "Cut too complex" or "Unable to reapply blends" - and that's all you get. Now as you gain experience you will be able to look at the model for "trouble spots" that are probably causing the model fits, but even then you must manually delete the troublesome geometry that you guess is causing the problem until you deconstruct the model the the point that you can make your desired change. Then you get to reconstruct what you deleted to get to that point.

It has been stated that Boolean CAD tools are simpler to use. That is probably true, because the user is shielded from having to understand embedded logic. Unfortunately, the solution to protect the user from this embedded logic has been to simply gut the functionality altogether. It is much like taking the tires off of my car and then telling me how great it will be since I won't have flat tires anymore. Well, true, but it won't drive so hot, either.

In my opinion the tradeoff is simple: With history, parametric based systems, you may indeed have to think hard from time to time when your model fails and you have to debug a failed internal relationship in the model. With non-history, non-parametric based systems, you have to think hard all the time because you and everyone behind you will have to understand and maintain all the design relationships manually.

If you absolutely have your heart set on playdough modeling, though, you might also want to check out SpaceClaim (www.spaceclaim.com). It may have an advantage in that at least it appears to have been created from the ground up as a new software package, whereas I always had the impression with CoCreate that it was a 3D modeler that had been cobbled together with their legacy 2D product, as the integration between modeling and drafting felt poor, though they have been making improvements over the four years I used it.

Steve

Steve
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