Wednesday, May 19, 2010

Explicit Parametric Concept Design

I know that most of you will consider the title of this post as being a contradiction in terms. I hope to show you otherwise. We are certainly seeing the makers of history-based parametric CAD tools attempting to add explicit like or direct modeling type functionality to their history-based systems. Unfortunately many complications can evolve in the model when direct geometry edits are made to a history-based model. Maybe someday the issues will be worked out. While this work is going on, makers of explicit or direct modeling systems are adding parametric modeling capabilities to the history-free model. Adding, managing and controlling “design intent” are not capabilities exclusive to a history-based modeling tool.

In the video example below I am showing some quick concept design of a fixture assembly, but while in the process I will capture some design intent as needed. Again in this case I am using CoCreate Modeling from PTC.
You will notice in the example that it makes no difference how the model is created, or how the assembly comes together. There is no up-front planning that needs to be done. History-free “design intent” has no dependency on how the models or assemblies were created or structured. As a matter of a fact, it makes no difference where the geometry actually comes from; IGES, STEP or even a 2D drawing. I can just as easily add design intent to imported models as I do with native models. Also, another user can easily interact with the design intent with no knowledge of how the model was created or how the intent was structured. The parametric solver in CoCreate Modeling is a synchronous solver. It is not a linear solver as would be the case in a history-based system. As such there is not dependency on the order that constraints and relationships were created. They are solved simultaneously.
You will also notice in CoCreate Modeling that constraints and relationships are not always necessary – and in many cases redundant. A mature explicit history-free modeling system must understand and leverage the properties of the B-Rep solid geometry to be of any value. If it does, it can use these properties intelligently to recognize geometric properties and greatly simplify the design intent solution.

I first hope you noticed how easy and fast it is to create and manipulate geometry, with no need for up front planning. Secondly I hope you noticed that design intent can be added independent of the modeling process.
I know most all CAD companies are trying to figure out how to provide their customers with the “best of both worlds” (history-based parametric & history-free explicit/direct). Will the “best” eventually come from a history-based system that provides direct editing? Or perhaps will it come from a history-free system that provides parametric capabilities?
Paul
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Some ways to learn more about CoCreate Modeling: