Direct modelling mania!

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‘Direct Modelling’ used to be just another relatively unpopular 3D technology. Now it seems vendors are falling over themselves to offer some direct geometry manipulation. Martyn Day gets his facets manipulated
I recently attended a seminar on SpaceClaim, a direct modelling design system launched in 2007.

SpaceClaim was backed by industry star investors and headed up by Mike Payne, the man responsible for the development of Pro/Engineer and SolidWorks. And while the creation of a new CAD system is rare and always big news, this one was backed by a team with great form, so the industry took note.

History-based CAD has dominated the mechanical CAD scene since 1985, when Pro/Engineer was released by PTC. Nearly every other mainstream offering since has been a variation on a theme,
should that be SolidWorks, Inventor or Solid Edge.

All the hype was about the benefits of parametric modelling, the potential for automation and good old moving from 2D to 3D and very few addressed the intrinsic problems of historybased modelling, or the huge complexities in creating and perhaps more importantly, editing fully parametric assemblies.

History-based modelling is a function of the computers of the time. Slow hardware meant it made sense to break down the construction of a part into individual step or features.

An edit to these steps would require a rebuild of the part to update each subsequent steps to arrive at the final form.

While powerful, it did give rise to issues with complex relationships. Edit a feature too drastically and things could quickly get out of hand.


There have always been alternatives such as CoCreate Modelling and IronCAD which offered ‘direct’ modelling.

These didn’t have the overhead of history-based systems and allowed model geometry to be directly manipulated. They also excelled at working with imported data. The problems came when working with non-prismatic shapes, such as surfaces.

Direct Modelling tools du jour were hopeless while history-based systems had the advantage that, by breaking down the construction of the geometry into individual steps, you could create and work with complex models. There’s clearly a huge mismatch in these two approaches.

History-based systems got out of the gate first, achieved market prevalence very quickly and so it has remained.

The likes of Pro/E, SolidWorks, Solid Edge and Inventor flourished and the direct editing tools never eally gained much traction outside of a few core industries – until recently that is.

Mike Payne

So SpaceClaim isn’t a new idea, it’s a new take on an old idea.

While it doesn’t resolve the inability for direct and history-based models to live together, it does offer great ease of use (aimed at non-CAD users and occasional users), an inherent ability to edit legacy data, and has the potential to become a competitor to the existing players.

My take is that the investors were hoping to sell out early and make a tidy sum, as had happened to Revit, their previous venture, but that didn’t happen. Instead the industry has gone ‘Direct Modelling’ mad and now there is a lot of hype to contend with.

PTC, which was first to be invited to see SpaceClaim, ended up buying CoCreate for $250 million. Siemens developed Synchronous Technology for Solid Edge and NX and Autodesk is developing Fusion.

Despite saying that nobody was asking for direct modelling in 2009, even SolidWorks has some capability in its Instant3D tools.

Within the space of three years, direct modelling has come from the backwaters of CAD to a key sales pitch function for all the players. I pointed this out to Mike Payne at the event, to which he replied acidly “Imitation is the sincerest form of flattery”.


The clear fact that’s being brought out of all this frenzy is that, despite years of development, the geometry problem is still not solved.

History-based modelling can’t do everything and new tools are required. The most recent developments have been trying to marry the history-based and the direct modelling abilities to provide some sort of workable system, as opposed to the design intelligence taking a one way trip to oblivion.

Autodesk, Siemens and PTC are all developing intelligent tools which allow the two methods to function together.

The history tree is the recipe of how a model is made and from it derives the geometry.

A direct modeller plays with the geometry without recourse to any parameters thus breaking the link. The new solutions attempt to rationalise the changes made to the geometry and topology and update the features as defined in the history tree.

I feel technologies are merging here to produce a new breed of even more intelligent design systems

However it’s still possible to make such edits that break the geometry.

In all the demonstrations we have seen, while impressive, the demo conditions appear uncomplicated. The direct editing of a complex fillet with various radii would cause most of these systems to keel over.

So while history-based parametric modellers are learning new tricks, developers are also making dumb geometry, less dumb.

At this year’s Isicad/ COFES Russia in Moscow, Dmitry Ushakov, LEDAS director of
product management, gave a demonstration of it’s Variational Direct Modelling (VDM) constraints system which when included into a direct modelling solution looks at the design intent and can create constraints and boundary elements in a featureless model.

Similar feature recognition technology is also being developed by companies like Geomagic that take dumb scanned data and automatically build feature-based solid models for intelligent editing.

I feel technologies are merging here to produce a new breed of even more intelligent design systems.


So, while Mike Payne has been at the core of history-based parametric CAD development, his latest venture, SpaceClaim has help push a signifi cant rethink in the industry as to how fl exible these design systems can and should be.

spaceclaim - direct modelling
Martyn Day says that the 3D industry has gone direct modelling mad!

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