Autodesk embraces BIM: Architectural Desktop vs. Revit
H. Edward Goldberg
Since Autodesk purchased Revit, a seeming competitor to its flagship Architectural Desktop, the AEC community has been wondering, “Where is Autodesk going?” Both products are intelligent building modelers with similar 3D capabilities. This month, I’ll clarify the structure and direction of each of these software solutions, anticipate future paths, and illustrate a recent implementation of BIM (building information modeling, a term coined by Autodesk and popularized by New York architect and industry analyst Jerry Laiserin) using Autodesk software.
Conceptually, BIM is a software solution that lets you embed a 3D building model with data such as material quantities and vendor information that pertains to components within the model. Other users later access and use this data throughout the construction and facility management stages of a project.
Autodesk recently explained in a white paper (www3. autodesk.com/adsk/files/3773752_BIM_in_Practice.pdf) how it differentiates among AutoCAD, Architectural Desktop, and Revit. The company sees BIM as an approach, not a technology in and of itself. Different projects may require different approaches, based on the most effective implementation of appropriate software solutions. Examples of these solutions, in increasing order of effectiveness (again according to Autodesk), are CAD, object CAD, and parametric building modeling.
CAD is based on a system of 2D electronic drafting that’s been used by the AEC industry for the last two decades. This technology effectively supports general 2D drafting automation and can create static 3D models. Though CAD solutions have increased productivity in the AEC arena, they require ever-greater levels of programming knowledge to continue to improve efficiency. In addition, the information coming from the CAD-based files depends heavily on the capability of the user. Most users prefer to use CAD strictly for drafting and contract documentation. With higher levels of effort, including programming and third-party partner products, you can retrieve building information from the documents. AutoCAD and AutoCAD LT are Autodesk’s CAD-based products.
Object CAD Technology
Object CAD simulates building components within a CAD-based environment, focusing on the 3D geometry of the building, the generation of 2D documentation from that 3D geometry, and the extraction of object data from the building components to provide information about quantities and object properties. This manipulation of CAD technology is sometimes referred to as a single building model or virtual model. Autodesk Architectural Desktop and Autodesk Building Systems are based on object
CAD technology, as are all products that support BIM. Because these products are based on AutoCAD (which, in my opinion, has become the de facto 2D electronic drafting standard), they can be used productively as design and documentation tools for 2D CAD drafting processes as well as building information modeling. Because AEC professionals are already comfortable with AutoCAD, they can easily implement Architectural Desktop or Building Systems without disrupting existing ways of working.
Parametric Building Modeling Technology
PBM (parametric building modeling) is similar to decision instruments used in the financial community that combine a data model (geometry and data) with a behavioral model (change management) that gives meaning to the data through relationships. Just as a spreadsheet is a tool for analyzing numbers, software built on PBM technology is a tool for analyzing buildings. A change made anywhere in a spreadsheet updates everywhere with no further intervention from the user. Likewise, a change made anywhere in a parametric model is immediately reflected everywhere. Also, all building information and a complete set of design documents are stored in an integrated parametric database and interconnected. This interconnectivity allows changes to the relationships, enabling real-time coordination of information in every view.
Autodesk believes that PBM technology is uniquely suited to support the highest level BIM effectiveness with the lowest level of effort. PBM provides concurrent and immediate information about the building. It can deliver tremendous business benefits, but using it requires a departure from traditional ways of working. Though you can move from CAD-based technology to object CAD technology incrementally or evolutionarily, PBM technology requires a new approach.
Autodesk Revit software is based on parametric building technology. It’s designed specifically for building industry professionals interested in BIM and the benefits that go with it. In contrast to Autodesk Architectural Desktop’s evolutionary path toward BIM capability, Revit has been a building information modeler from its inception.
Autodesk Drives Revit Forward
Autodesk continues to rapidly develop and expand Revit’s capabilities, both as its most technically advanced architectural BIM application and as a platform for an expanded BIM application suite. In December, the company announced Revit 6. Recognizing that it may take years for Revit to become the new AEC documentation standard, Autodesk also now offers Revit and AutoCAD as a bundled solution. Revit is interoperable with AutoCAD. For architects with an investment in AutoCAD-based workflows and training, this is a great way to migrate to BIM.
Design options. BIM is a terrific design tool. 3D views, renderings, and other presentation documents are a by-product of the building model. And in parametric BIM, relationships embed design rules in the model, so as you adjust the building, important relationships are preserved. Revit 6 lets you work simultaneously with multiple design options in a single model, making it a tool not only for design but for design thinking.
Multi-user element borrowing. One of the greatest technical challenges for a parametric building model, which is based on either a single or limited number of actual project files, is project sharing between users. For some time now Revit has offered a Workset multiuser mode, which lets you share a model with team members.
Revit 6 introduces a more fluid, intuitive collaboration mode that dynamically assigns any selected set of individual building elements to separate users on-the-fly, while continuing to coordinate all changes by all users in the shared building model.
Customizable project browser. This is one of my personal favorites. Revit’s project browser has always organized all of the building models in one convenient, easy-to-use tree-based structure, but as projects grew the browser structure sometimes made it hard to manage all the information. Now Revit’s project browser organizes the building model any way you like, with filters to help you sort and reassign groups of views.
Interoperability. This one is for you technical folks out there. What good is a building model if you can’t share the data? The Revit team has recognized the importance of this by supporting industry-standard data protocols such as ODBC, as well as common geometry file formats such as DWG, DXF, DGN, and DWF. However, the connection between the data export and the geometry has always been a challenge. Revit 6 indexes all of the building information between the database and geometry output, enabling in-house and third-party applications to take advantage of the building information in the model.
All bases covered
Autodesk offers products based on all three building design and documentation technologies–CAD, object CAD, and PBM. Because the building industry relies heavily on graphical information, some aspects of these three technologies appear similar at the presentation level. For example, all of them capably represent building plans, sections, and elevations. Construction documents may appear the same, but the underlying capabilities are vastly different.
Today, BIM is cutting edge. Tomorrow, as architects. engineers, and their clients recognize its value throughout the design, construction, and facility management phases, the building model will become an industry standard. In addition, Autodesk just announced AutoCAD 2005, which will take this program to a new level of CAD automation. Regardless of which type of technology meets your company’s current needs, it’s a good idea to keep tabs on new developments in all three approaches to architectural design software.
Fentress Bradburn Architects use autodesk software to deliver BIM
Recently Fentress Bradburn Architects, Ltd., of Denver, Colorado (www.fentressbradburn.com), completed its first building modeling project for the GSA (Government Services Administration). The award contract for the Cape Girardeau (Missouri) Federal Courthouse project in March 2003 called for the inclusion of BIM information on walls, doors, windows, and stages in property set data. GSA project managers wanted to be able to alter the data and do what-if estimates using different material vendors. This level of BIM is well suited to object-based technology, which lets you extract object-level information from the building model.
Fentress Bradburn Architects selected Autodesk Architectural Desktop 2004 to enable them to fulfill the contract terms. In my interview with Mike Rinken, IT manager, and Tracy Matteson, CADD manager for Fentress Bradburn, they reported that the process was so easy they added more information than required to the building model. Fentress Bradburn is a 25-year-old architectural firm known for being at the cutting edge of technology. Until 1991, the firm used MicroStation, but since then has used AutoCAD and Autodesk Architectural Desktop. Rinken and Matteson noted increased productivity during the design stage–Architectural Desktop’s scheduling capability helped them track doors, material components, and related rooms.
Fentress Bradburn is now using Architectural Desktop to reconstruct documents from a previously completed construction project to compare the object-based building information with the actual construction cost. The firm wants to do an entire BIM project, including HVAC, electrical, and mechanical, with Architectural Desktop and Autodesk Building Systems. According to Rinken and Matteson, the GSA is interested in a complete model, including all trades, on some future projects.
* “New Tools Deliver BIM Data,” December 2003, p. 34 (www.cadalyst.com/cadalyst/article/articleDetail.jsp?id= 79482)
* For more articles on BIM, see past issues of Cadalyst AEC Tech News Newsletter at: www.cadalyst.com/cad alyst/article/articleList.jsp?categoryId=3251
H. Edward Goldberg, AIA, is a practicing licensed architect, industrial designer, and AEC industry analyst. Find Ed’s new book, Autodesk Architectural Desktop 2004: A Comprehensive Tutorial (Prentice Hall, 2003) at www.prenhall. com. You can reach Ed at firstname.lastname@example.org. Or visit his Web site at www.hegra.org.
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