Today I came across an e-mail informing me that Autodesk had released the new 2011 versions of their CAD and BIM software, AutoCAD and Revit. If you are familiar with these products feel free to skip the following two paragraphs for my opinion about BIM and CAD, if not, read on.
For those of you who are not familiar with the world of architectural software it is broken into two different conceptual models: Computer Aided Drafting (CAD) and Building Information Modeling (BIM). CAD software has been around since the 1980’s and is a digital analog to hand drafting. In it, users work in either a 2-D or 3-D environment defined by points and lines (or vectors). CAD software is a time saver in that instead of each drawing being an independent sheet that needs to be redrawn whenever changes are made, the drawing lives virtually within the software and changes can be made rapidly without effecting other areas of the work. In addition drawing elements can be quickly scaled larger or smaller to create details or other drawings. Since CAD is a replication of the drawing process it is used by many different industries. For three dimensional work it can be clunky and hard to understand; to remedy this companies like Autodesk created add-on programs that extend the vector based system using pre-made and user definable blocks and proprietary elements indexed by a database to automate the three dimensional process. This system has its uses, but cannot compete with true BIM software when it comes to three dimensional coordination.
BIM is almost as old as CAD, but has only recently started to become a mainstream tool. If CAD software is the digital analog of drafting, BIM software is the digital analog to model making. BIM uses a database of elements to define space: instead of drawing two lines to represent a wall, or using a wall tool to create a series of lines and surface to represent a wall, in a BIM system a user models a wall by selecting an element from a database and defining its values, like height, length, material components, etc. The element that appears in the program looks very similar to what you would find in a CAD program, but instead of being defined by its fixed points and vectors, it is instead being built from a database element. This allows individual elements in the building to be categorized and identified much quicker and allows for a higher level of integration. Instead of just defining a wall as X feet high, you can define it as running from floor 1 to ceiling 1, this way if the distance between floor 1 and ceiling 1 changes the wall changes without the user having to make any other corrections. This system can take lot of time and effort in the beginning to create a model of a project, because every major element needs to be present. Once the skeleton is in place, though it saves an incredible amount of time, because elements can be augmented at will, and, at least in theory, everything will adjust. This system can also be automated to produce warnings when elements intersect in ways that are not desired, which can be a godsend when coordinating multiple construction disciplines (architecture, mechanical engineering, plumbing, structural, etc.).
Since I recently started my own firm, I have been looking to buy software to automate our design process. In previous jobs I’ve used AutoCAD Architecture and in school I used Revit, so I am comfortable working in either CAD or BIM. The real issue for me is a cost benefit analysis. CAD software can be as inexpensive as the new version of Autodesk’s 2-D only non-enhanced software,AutoCAD LT, priced currently $900, or can ballon up to Autodesk’s expensive, but powerful, 2-D and 3-D software with architecture specific modeling tools, AutoCAD Architecture 2011, priced at $4995. On the other hand, Autodesk’s Revit Architecture 2011, one of many discipline specific varieties of BIM software, is priced at $5,495. To me as a small practitioner, the cost of either AutoCAD Architecture or Autodesk Revit is prohibitive when I have the option of software at 1/5 the price. On the other hand, if I was going to buy higher end professional software that can automate my tasks I cannot see a reason to by AutoCAD Architecture, for $600 more I could start working in what is sure to be the new method of construction design. In addition, the hardware requirements for AutoCAD Architecture or Revit far outstrips any machione I currently have, and would require an additional $2000 purchase. Now, of course, if I was an existing office the choice would be a lot more difficult, if my files and previous projects were all AutoCAD based, and my staff was all CAD trained, BIM might seem like an unreasonable hurdle to overcome. Thinking about this makes me wary of buying AutoCAD LT, because even though it is a reasonably priced entry level piece of software, if that is what I start my business with when I am ready to move to a higher end piece of software I may find myself trapped by my future staff’s ability and my past projects.
So, for now, I will content myself with hand drafting until I find either a profitable contract to offset the infrastructure purchase of a high end machine and revit or find myself wasting too much time revising a project and break down and buy the lower end software.
2 thoughts on “To BIM or not to BIM that is the question”
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