BIM There, Done That18 Oct, 2006 By: Scott MacKenzie
Straight talk about what it's really like to move from CAD to building information modeling
Are you still wondering, “What's the deal with BIM?” If you don't know the acronym by now, it means building information modeling. Personally, I think it isn’t as good an acronym as VBD (for virtual building design and documentation). But VBD isn't as compelling and, well, it reminds me of a disease, so we'll stick with BIM.
2D to 3D
My CAD experience goes back 17 years. I started on AutoCAD Release 9 and I have used four other CAD brands along the way. I had 12 years of production CAD experience before I did any chargeable work in 3D. When I was hired by a large architectural firm in 2000, they wanted me to take them out of AutoCAD R14 and into ADT 2i (Autodesk Architectural Desktop 2i). It was not an easy transition. I had little problem with the software personally because I saw great value in the drafting automation, but some of my coworkers were hesitant. Architects who were used to the status quo, and folks who probably shouldn't do CAD at all, had some trouble with "going 3D."
In my opinion, the drafting automation is great in ADT, but the 3D component forces the architect to change his or her approach in the process. And this was cause for concern and fear. The concern was justified, and we needed to digest the new technology carefully. Some people were scared, because it meant they had to learn a new tool and a new way of doing things, and follow some new rules. Oh, no!
As a CAD manager, all I wanted to do was make the process of getting the information on the drawings more efficient. The fact that ADT would clean up walls, doors and windows made it worth the change to me. But the deeper we got into ADT, the harder it became to control -- at the time, it was too difficult for most users to handle. There came a point where it just didn’t make sense for us to advance further into the capabilities of the software, so we stayed with the basic functionality of ADT and only used the walls and doors.
3D to BIM
The next alternative was to move to BIM. Keep in mind that 3D design is not necessarily BIM. BIM is 3D, but in addition it’s a virtual building paradigm involving parametrics and relationships. (Yes, I said “paradigm.” Sorry -- it's such a corporate buzzword.) Moving from CAD to BIM is even more challenging: In addition to the issues explained above, you have to address the users' tendency to approach the BIM process like a CAD project. A BIM project has to be approached differently or you will be in for trouble.
If you do “go BIM,” change will come in numerous ways:
- Everyone in the documentation process has to change their perspective and routine.
- Project managers have to change staffing to accommodate more work in the early stages of the project.
- Project architects/engineers have to be more involved with the drawing process.
- Production BIM users need to become team players and better communicators.
- CAD managers have to provide better templates before work begins and spend more time engaged in project setup.
The first time I saw BIM was in a demonstration of Revit 3 (before Autodesk bought it up). I thought it was pretty cool, but I didn’t feel that it was a good solution for me or my office. When I saw Revit again,at version 5.1, I was hooked. I was able to clearly see how Revit would save me time and headaches when it came to managing the project. The architect would benefit too, because of the parametric environment. And it was easier to utilize the advanced features of Revit than those of ADT. I showed this new way of life to my office, and with the help of our corporate CAD director, we engaged in our first BIM project.
Managing BIM: The Challenges
Managing in this new BIM environment simplified coordination of stories, plans, elevations and sections. We didn’t have to manage nearly as many files, and layer management was not an issue -- because Revit doesn’t manage via layers! No layer management for the CAD manager? Just think, no more layers named "walls-old2" or "bobs-stuff." I thought that was one of the greatest things since drawing software was invented.
That being said, it was not an easy transition -- especially once we started putting more than two people on a project. Revit's model-sharing paradigm is fairly easy to conceptualize but difficult to practice. People are not accustomed to sharing their CAD files. It's almost like teaching a two-year-old to share: It’s a new concept, hard to fathom at first. Some people will whine and complain, but don’t give up.
Also, ideally, you'll also need to facilitate real-time communication between team members. In a shared model (Teamwork in ArchiCAD, Worksets in Revit), many people can be working in a model simultaneously. Inevitably, you'll need to work on something that is already in use by someone else. Bring your whole team within talking distance of one another, if possible. If you can't do that, implement an instant messaging application, which provides a communication line that is fast and undisruptive. Instant messaging is a touchy subject for most IT personnel, but they will have to adapt to the new paradigm too, if you want to be the best you can be.
Maintaining existing CAD standards can be a problem. It is best to rethink everything based on what the new BIM software gives you, without customization. Model management is also important. You'll need someone to manage and maintain the BIM folders and files. More so than with CAD, BIM projects are affected adversely by user error and stupid file and folder naming.
You may be thinking that all your CAD users can just jump in and start drawing, but a competent user base is essential for success. You must invest in good training from experts. Put only your most competent people on your first few projects. No whiners allowed, either. In addition to selecting the right people, front-loading a project is essential. Before you start, you must know what you need to build, have a good template system set up, and have your environment ready (to the best of your ability). Drawing habits need to be kept in check. Now that you can do 3D work more easily, don't get sucked into lots of cool detail work. Draw or model only the level of detail you need. Too much detail can really slow your drawing environment, and that means all your workers will be slowed down too. My suggestion is to model only what you need to see at your most prevalent scale. That would be 1/8" = 1'0" for commercial buildings. If you can't see it on an 1/8"-scale floor plan, then don't model it! You can add your detail line work in your large-scale plans, sections, elevations and details.
Remember, the actions of one member can greatly affect the whole team. The BIM model is more like a living body than the CAD file is. One change can transmit a reaction throughout the entire body. Take good care of your bodies.
Revit to ArchiCAD
I have been using Graphisoft's ArchiCAD 9 and 10 for a year. ArchiCAD is a BIM package that has been around for a long time; it's just not very well known here in the United States (compared with Revit and AutoCAD). I work for CUH2A, a large architecture, engineering and planning firm. We chose ArchiCAD over Revit and other software options because of the way it can handle a large project.
Everything I learned with Revit applies to ArchiCAD, except the part about no layers. ArchiCAD has layers, but with a good control mechanism known as layer combinations. However, I like ArchiCAD because of the menu customization it offers. Plus, there is a good selection of third-party software available.
Worth the Effort
In my opinion, BIM really is a better solution for drawing buildings. If you take the time to learn the way it is supposed to be used, and you don't try to manage it like you would a CAD project, you’ll be happy.
I didn’t even mention the benefits you'll get from calculations and quantity takeoffs. Or how changes to the plan will update automatically through the sections, elevations and details. You will just have to discover all that cool stuff for yourself – or read about it in a future issue of this newsletter.
About the Author: Scott MacKenzie
Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!