Direct CAD News & Views from Kubotek USA

What is Direct Modeling?

Posted by John Agoglia on Fri, May 09, 2014

dead ends resized 600What is Direct Modeling?  That could be the most common question we encounter.  The answer to that question usually depends on what you already know about Direct Modeling - or in some cases, history-based modeling, or for others, perhaps what you know about CAD in general. (After all, everyone has a different level of proficiency with CAD and knowledge of the CAD landscape.)  So, to help you out, here is a list of things that define what Direct Modeling is...

1.  Let's begin with what Direct Modeling isn't.  Direct Modeling isn't parametric-based.  It doesn't rely on history-trees to build a model.  If you're used to parametric modelers, such as the ubiquitous SolidWorks, then you don't get to experience the joy of rebuild errors and red X's populated your tree (and yes, I'm being a bit sarcastic). 

To that, I usually get one of two responses:

  1. Oh, I HATE when that happens! Or,
  2. What?  How do you make changes if you don't have a history-tree? Which brings me to...

2.  With Direct Modeling, if you have geometry, you can work with it.  Regardless of whether you created the geometry or imported a design from someone else, you can always make changes because a direct modeler is smart enough to know what the geometric features are. Simply put, Direct Modeling is like electronic sculpting.  A little bit off here, add some more there, make this rounder, make that longer, no wait, instead of rounder, it should be square, and so forth until Voila!  Your design is finished.  And nothing broke down and you never had to start over from scratch.

3.  Direct Modeling can be as simple as cut and paste.  If you want to remove an entire piece of the model and place it elsewhere, copy the feature or set of features and with a few simple moves, place it where you want it. No digging around in a history-tree to recreate the steps. And certainly no worries about breaking the rest of the model.  See point #2.

4.  Similarly, Direct modeling lets you manage your design easily be allowing you to point to a specfic dimension, feature, etc and then easily make changes either by "directly" pulling or pushing or cutting and pasting (prune/graft in the CAD-speak world).  See point #3.  Or, if you want, you can command the model to do what you want by simply typing in a dimension - the changes happen in real time.

5.  Direct Modeling is full-featured CAD.  Want to work in solids?  Wireframes?  Surfaces?  2D?  What about assemblies?  Direct modeling is fully capable to do all these things.  Don't be fooled into thinking that Direct Modeling isn't for the "serious" engineering or manufacturer.

6.  Direct Modeling is an easy transition from 2D drawings into the 3D modeling world. The approaches are very similar.  For people who already know how to program a parametric system to spit out a 3D model, you'll probably see a learning curve of about 1-3 days, depending on your skill level.

7.  Direct Modeling is a close to "plays well with others" as you can get with CAD software. That means that a Direct Modeler will accept not only neutral formats like IGES and STEP, but it will also be able to read in native CAD files of almost any CAD package available.  Output is pretty awesome, too.  Obviously, you can output in neutral formats, but you can output in a select number of native formats, as well as 3D PDF and image files.  The only limitation to a Direct Modeling file is the parametric system that others will use to try to read your Direct Modeling file.  Since most parametric systems don't want to accept any file but their own, they become the kid who always throws a tantum when he doesn't get his way.  But again, that's their limitation, and not a fault of Direct Modeling.  Don't be that kid who only wants to play on his terms and no one elses.

8.  With Direct Modeling, your model is represented by the geometry on the screen, not the words in the tree.  Direct Modeling simply doesn't need the steps conveyed in the history tree.  The tree isn't your model.  The model, or the geometry, is your model.  The tree is essentially the steps, the formula, the recipe that drives the software so that the software knows what to draw on the screen.

Direct means to command; to administer or manage; to point, aim or send toward a place or object.   The short of it is, you're the boss of the geometry on the screen.  You're not held captive by the software in any way, shape or form.  By gosh, if you want to edit your design - or anyone else's design - Direct Modeling will let you, not questions asked, and no resulting failures in your feature tree.