Direct Modeling?

I’ve been looking at direct modeling recently and I’m unsure exactly what it is. What programs use it? Where is it used in Product Design? And is it the future?


It’s kind of the opposite of build tree based programs like Solidworks. In direct modeling if you want to change something you directly grab and move the part you want to change. in a parametric program like Solidworks you go to that step in the build tree and change the inputs and hope the model doesn’t “explode” due to the subsequent steps not rebuilding correctly after the changes. The advantages of direct modeling is that you can edit a model without having to study the way the build tree is put together, so it can be good for working on files started by other people. Is it the future? I don’t know, but it is a useful tool in a designer’s tool-belt.

Direct Modelling in the most basic sense is manipulating 3D geometry directly, like pulling control points in a tool like Alias or Rhino. You are “Directly” editing the model, rather than adding a parametric constraint (like a new curve to define a surface bulge).

Is it the future? No. It’s been around since the dawn of NURBS. Are people embracing it more? Possibly. You see PTC adding these types of tools to Pro E/ISDX now to allow direct surface manipulation to modify your design.

The advantage is it is most analogous to sculpting by hand. You can push and pull CV’s in a very delicate fashion to achieve very specific design intent, whereas with parametric modelling you are usually building very detailed cross sections of a surface and then letting the software compute the result. Here you are the one modifying that result.

For my workflow almost all modelling is done in Alias with these methods and then transferred to Pro E to have parametric features added for engineering. When done correctly it is quite robust, albeit more complex than just building a model in one package.

I thought as much. Are Creo and NX examples of direct modeling and parametric modeling together?

When I meant the future, I was really referring to these programs that use direct modeling whilst updating features on the fly (eg Creo / NX). They’re mainly used in engineering and specialist design fields but I wondered if, in future, these techniques were likely to filter down and become widely used throughout the Product Design industry.

I don’t have much experience with NX, but Pro-E/Creo is an example of doing both.

Frankly, I think in general the industry is fairly slow to change. If you use Pro E you will probably keep using Pro E and if you decide to leverage those direct modelling features it would be up to the end user.

There are definitely companies out there doing direct modelling though. Any company that uses Alias is probably doing some variation of a direct modelling workflow.

I think that these techniques will become more widespread. It’ll be interesting to see what Solidworks has in store for their next version and if they make a big advancement in freeform tools.

Playdo: Take a look at SpaceClaim… I wouldn’t say that it has the capabilities of a full out surfacing program, but in terms of geometry manipulation you’d be hard pressed in any of these other packages to do what they are doing as easily.

There is also Solidedge with ST4 just coming out. This is the only CAD package that truly let’s you go back and forth between a modeling system that is DE or Parametric. Now take this with a grain of salt in that being able to make any changes one wants without having to ‘think’ about the consequences seems a bit over reaching. Programs like SW/SE/Pro.E make you think about how something should be manufactured. Programs like Alias/Rhino/Modo just let you model whatever a user wants and not really have any consequences to their actions . (I say this loosely because it really comes down a users understanding more than anything else) But the initial use of the programs don’t really have the ‘rules’ put in place to prevent that from happening. This frustrates the hell out of new users, having to follow the ‘rules’, but I’m of the mind state that it can be one of the items that make you a better designer/engineer.

SW does have the ‘instant 3D’, but that’d a reach if one were to call it DE. Maybe you might call it DE 1/2…

Creo ‘looks’ promising…but any video hype is promising. It remains to be seen that now it is out and ready to be in the hands of users just how robust their ‘DE to P’ system it, or as they are calling them “Apps”.