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From CAD User AEC Magazine  Vol 20 No 02 - FEBRUARY/MARCH 2007

David Chadwick looks at the dynamic modeling technology behind CoCreate's OneSpace Designer

It is fascinating to see some of the new features that are being introduced into leading 3D modeling packages, aimed at easing the transition from 2D drafting to 3D design, and simplifying the task of creating and modifying 3D models for those without extensive expertise in that particular package. Fascinating, because whatever name they give them, the new features resemble those that CoCreate has been using for years in its OneSpace Modeling - Dynamic Modeling! Most CAD software developers now realise that history-based 3D models - all of the information about the model, that traces each step in its history, incorporating parameters, constraints and other dependencies - can become vast, complex entities, capable of being fully understood only by the originator of the model - a highly trained 3D CAD specialist. In the current climate of collaboration, this is inimical to any degree of co-operation on a design. Instead of being able to download and work directly on the 3D model, other design engineers are having to recreate much of the models from 2D data (a fact testified to by the Automobile Industry in America, where they claim that over $1billion is wasted in this way). The problem is exacerbated by increased outsourcing of design components. Much of the 'design data' is lost in transferring model files from one of the many CAD solutions to another. The end result is that the amount of money that companies spend training up their specialist 3D capable design engineers is not reflected in a comparable rise in profitability, and that many companies still rely on 2D design. Dynamic modeling, provides an alternative solution. It provides a history free design environment that is easy to learn and use, and that allows 3D models to be shared across development teams. Novice, or infrequent users can be up and running within a matter of days, and all team members can share and refine, or re-use design data, without having to learn history trees and hidden dependencies .

So what are the differences between the two approaches? It's quite simple really. A history-based model comprises all of the steps needed to make the model in a detailed history tree - an accumulation of all of the sequences used to create modeling features. If a designer wants to modify the model, he has to be aware of the steps involved in creating the original model. In some cases, a modification can only be achieved by going back through the history tree, modifying not just the feature, but also its constraints and other parameters. This can have unanticipated side effects, so that the model is unable to regenerate, and the designer has to re-define features, histories, constraints and change relations and references - and, in effect, rebuild the model! Contrast that with the dynamic modeling approach, where the feature is selected, with no reference to how it was made, and the change is applied. Finito! Actually, that makes it sound as if dynamic modeling software is not sophisticated enough to develop complex products and assemblies, or use advanced design tools. Nothing could be further from the truth! Besides being used to create the geometry, the software can also be used to perform complex topology modifications, or, using automatic and user-defined feature recognition, accompanied by dynamically defined relationships and parameters, rapidly modify the most complex of models. The benefits are many. It allows design teams to refine and re-use existing models. It allows modification to be made to models even at a late stage in the design process, and allows designers to explore design alternatives. New staff can be added to the design team, and can start working on the same designs almost immediately - and casual users (none more casual than myself) can dive in and use the software without having to relearn the system.

It also allows designers to work on 3D models from other CAD systems, with close to full productivity. CoCreate uses translators on imported models to ensure the highest quality of imported data (or you can use STEP or IGES). Sharing designs between history-based modellers, however, typically allows only about 50% access to features and constraints. Dynamic modeling users can leverage up to 95% of the existing data - and, on top of that, key features on leveraged design data can be redefined. OneSpace Modeling uses dedicated data adaptors for sharing data. This can even extend to assemblies and parts structures, which, maintaining assembly and positioning information, can be dragged and dropped into existing assemblies for re-use. When you do this, clash and interference analysis tools can be used that show volumes of interferences, to show where they clash. Design changes can also be made to accommodate other requirements - when you want to create tooling form the model or, an area that causes problems with 3D history-based models that are derived from various sources, when you want to use the model for design simplification, drawing generation, FEA analysis or model management.

You may wonder why, with the advantages claimed above, did developers opt for history-based or parametric modeling? This is probably because Direct Modeling, a forerunner of dynamic modeling, was quite limited, and could only be used for simple editing, and restricted modification to existing models, and not for creating new models. Direct modeling also built up a sequence of model creation steps, similar to that of history-based modeling, and, eventually succumbing to the same problems. Dynamic modeling evolved in the early 1990s, five years after the introduction of history-based modeling, using patented, order-free modeling techniques. What users see on the screen is what they get, the topology and the geometry - there is no hidden intelligence. The intelligence behind the changes comes directly from the user, not the CAD model file - providing a powerful set of design capabilities. This has evolved into an alternative 3D modeling tool that provides a full range of 3D modeling features comparable to any other history-based product on the market - including the ability to create 3D assemblies with variable dimensions, simulate physical motion and animations, and create 3D inspection plans.

The proof of the pudding is in the eating. Having used only history-based modellers in the past, I downloaded OneSpace Modeling, and jumped straight in! Well, not quite - the CoCreate web site provides some useful demonstration videos and presentations, so I wasn't going in totally blind. The screen is simpler than others I normally use, with fly-out boxes whenever a set of functions are called from the (slightly unfamiliar) icons on either side of the model space. These provided all of the options available, the option to set parameters for some of the functions and, if I wanted to use it as well, a model browser! My aim was to recreate a simple demonstration that epitomised the dynamic modeling technology. This was to create a simple rectangular shape, sketch a rectangle and a couple of circles on the surface, extrude it and then shell the result. All very rapidly and intuitively done. The next part brought in OneSpace Modeling's feature recognition capabilities. I was able to select one of the features that I had just created, using simple free-form modeling, and move it in its entirety to a new location in the shelled box. Similarly, after selecting the chamfer tool and applying it to one of the edges, I was able to manually draw it out to the dimensions I wanted, see a preview of the chamfer or edges, and then tick to accept it - and then apply a similar chamfer around all edges! Simple stuff, but enough to demonstrate the dynamic aspects of the modeling process. And enough to enthuse me to dive right into the latest version of the software -and its accompanying data management tool, OneSpace Model Manager - for a full product review in the next issue of CAD User. CoCreate now offers 3D Modeling absolutely free with OneSpace Modeling Personal Edition. If you are not familiar with Dynamic Modeling you can now test it for free. Simply download the OneSpace Modeling Personal Edition (see below).http://www.cocreate.com/gratis

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