Maissoun Ksara - B2: Chapter 2 - BIM Tools and Parametric Modeling

Object-based parametric modeling is the ability to define an object based on geometric and non-geometric principles, which can be automatically changed when a dimension, value, or property of that geometry is modified. It also allows modeling of objects with relative rules such as “parallel to, attached to, and distance from”, as stated in Chapter 2. For example, DesignTech illustrates this by saying in order to “modify a 3D solid, the designer had to change the length, the breadth and the height. However, with parametric modeling, the designer need only alter one parameter; the other two parameters get adjusted automatically” [1]. This is accomplished through a hierarchy of parameters at different levels. According to the BIM Handbook, this gives the possibility of introducing highly complex geometries into modeling very simply. BIM tools such as Revit, Bentley Architecture, and more use  object-based parametric modeling tools for design. 

Companies like Boeing have incorporated parametric modeling in the design of their products. The interior of the 777 airplane is defined by rules set by Boeing, and the outside shape uses Computational Fluid Dynamics (CFD). About $1 billion dollars was spent to develop the parametric modeling system for the 777 airplanes (so expensive!). 

PTC provides a helpful pro/con list for parametric vs. direct modeling that I found helpful [2]. Ultimately, it was concluded that a combination of both parametric and direct modeling is the most beneficial for producing new designs.

[2] Parametric Modeling

(+) Pros

• Automatic model updates when changes are made to design
• Creation of families of different parts automatically
• Quicker production time due to good integration with manufacturing procedures

(-) Cons

• Takes a long time to update after changes are made

[2] Direct (just-do-it) Modeling

(+) Pros

• Quickly create new 3D models
• Quickly edit geometry

(-) Cons

• Dimensional editing is weaker
• Design automation is very weak

According to the BIM Handbook (Chapter 2), the best known software that uses BIM for architectural design is Revit (structure, architecture, and MEP). This is due to Revit’s simple and easy to learn interface with an open library. However, it is noted that the software can get slow for projects bigger than 220 MB since it is an in-memory system. It is important to distinguish that object-based parametric modeling does not equal BIM tools. It is a component of BIM that plays an important role. 

In conclusion, object-based parametric modeling has changed the way the building industry designs its structures. It provides a simple, and easier method of developing highly complicated building models. 

References

[1] https://www.designtechsys.com/articles/parametric-modelling.php

[2] http://www.ptc.com/cad-software-blog/parametric-vs-direct-modeling-which-side-are-you-on

Comments:

Ronald Herazo: The use of boolean operations has definitely changed the game in terms of design. It allows for a much more streamlined process for creating complex shapes in a quicker way. Boolean operations are important to learn, and are tools I’m looking to develop for my own skill set. It is funny that you say BIM has existed since the 70’s, since it is just recently becoming a craze. It took a while for companies to start actually using BIM. I wonder what caused this sudden popularity.

Nick Pawlikowski: Reading your post really helped me understand interoperability and its uses. I can see the benefit of interoperability, as it allows for the exchange of data between different applications. This allows for the more efficiency on completing a single task. This removes the necessity of creating translators, as you mentioned in the case for NASA. The use of EXPRESS language relates to my post on object-based parametric modeling. The figure showing the common formats in the AEC industry is helpful and shows which formats are most readily used in what industries. 

Taryn Francishetti: In my post, I also talked about how Revit slows down once the file size becomes too large. This is unfortunate since Revit is the most common BIM design tool used today. I wonder if the Revit suite is undergoing updates or if it is possibly being redesigned to be able to handle more in memory space. I don’t really know much about Digital Project, but I’m thinking of reading about it to see its benefits. I think your post defines BIM and explains it really nicely in a way that is very simple and straightforward.