Cadalyst - March 2008 - (Page 37)

mcadmodeling nents, pumps, gears, and whatever. (To be fair, you see a lot of companies nowadays expanding their offerings to include parametric models, in multiple file formats.) If you are going to buy something made by someone else, you most likely will not want or need to make changes to the geometry. Most often you are just going to model around it and include it in your designs. But what if you do need to change something? What kinds of things can you do with nonhistory-based models? But What If . . . Most every nonhistory-based modeler worth its salt is capable of making changes to nonparameterized data. And it has many ways to do it, too. I came from a nonparameterized past, and I’m perfectly comfortable editing that kind of geometry — provided I have the tools to do it. Many programs allow you to edit a model without a history. On the history-based side of the modeling street, Siemens PLM Software’s NX software can make wholesale changes to nonparameterized data. So can SolidWorks. On the nonhistory side, Kubotek’s KeyCreator uses what they call directrace manipulation (figure 3), which lets you make changes to geometry without regard to how or where it was created. You just select what you want to move (the faces) and where you want everything to go, and the model obediently updates, usually without a hitch. Most nonhistory-based modelers have this kind of capability. Programs that let you straddle the line between history and nonhistorybased modelers are called hybrid modelers. They can be history based or not, and they can work with just about anything. I like these programs for their wonderful versatility. You aren’t as limited as you would be using a system that makes you choose one way or the other. I like how you can more fully define your solids in some systems by adding constraints directly to the model’s geometry. In a parametric sketch-based system you can only constrain what’s in the 2D sketch. Consequently, it may be difficult to firmly establish just where a particular dimension is going or to what it pertains (figure 4). Also, you have to capture any other information outside the sketch — where it can be a challenge to find and edit. For instance, you have a boss feature. How tall is it? What’s its diameter at the top? There is no sketch — it was made with a boss feature. You have to go in and query the boss feature through the edit command. Want to inherit that information onto the drawing? Forget it. It’s not available. You’re going to have to create those dimensions the old-fashioned way. Programs like CoCreate’s OneSpace are nonhistory based but still allow you the flexibility to make some pretty parametric-like changes to geometry (figure 5). Figure 3. In most nonhistory-based modelers, you have ways to change just about anything in your imported geometry. In Kubotek’s KeyCreator, you can edit faces directly and move them wherever you want merely by grabbing them and telling them where to go. Figure 4. Some modelers — in this case, Kubotek’s KeyCreator — let you establish parameters after the fact and right on the geometry. How to Choose? Figure 5. CoCreate’s OneSpace modeler lets you make changes to models that have no parameters because it sees all geometry The ultimate question to answer when as native OneSpace geometry — no matter where it came from. choosing between a history or nonhistory-based modeler which is superior. They are merely difis, “What do I intend to do with the ferent ways to get the job done. And models?” Each method has advanisn’t that really what you’re after? c tages and disadvantages. If one will work for what you want to do, then Mike Hudspeth, IDSA, is an industrial use it. If not, don’t. I don’t really think designer, artist, and author based in St. there is an iron-clad rule to determine Louis, Missouri. www.cadalyst.com | cadalyst | March 2008 37 http://www.cadalyst.com

Table of Contents Feed for the Digital Edition of Cadalyst - March 2008

Cadalyst - March 2008 Contents Editor's Window CAD Central Thicker than Water Safe Keeping — Backup Software Secures Your Designs AMD’s ATI FireGL Graphics Cards AutoCAD Civil 3D 2008 — Surveying, Civil Engineering, and Land Development Software Cool Software Utilities for Your Job History, Nonhistory, or Both? In the Eye of the Storm Builders’ Information Modeling CAD Cartoon Issue Indexes CAD from the Streets

Cadalyst - March 2008

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