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Old 04-09-2007, 11:30 AM
Steve Steve is offline
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Join Date: Mar 2003
Location: Alabama
Posts: 309
Re: Cadalyst - MCAD Modeling—History . . . or Not?

Quote:
Execel is not "history based", but "relationship" based.
The thing is, in the CAD world, "history" is the means by which you define features to which you then assign relationships.

Without history, you cannot define relationships to theoretical geometric constructs.

The classic, trivial example: Applying taper to a cylinder.

Let us say we have a cylinder, and then we apply taper to it, but then we wish to change the diameter of the underlying cylinder. A non-history based system cannot do this, because it doesn't "remember" that there was ever a cylinder present. But a history based system does, so it is trivial to modify the basic diameter of the now-tapered cylinder.

In a more sophisticated example, history is what allows you to define features which only exist at certain levels in an assembly. This is what allows you to create machined components based off of a casting.

History and Parametrics are closely intertwined and equally important to be able to adequately capture and imbed design logic in a model. Parametrics are the dimensions, history is what allows you to dimension to underlying theoretical geometry. Without history, you cannot apply parameters to what you need to control.

Steve
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