Revit now supports Microsoft XP's 3 GB switch. Use of this setting will give your machine more RAM to draw from before it goes to virtual memory. Windows XP allows any given application access to only 2 GB of RAM at a given time; if the application needs more, it gets the rest from virtual memory. Microsoft's switch (which is available in XP Service Pack 2) allows you to change that 2 GB limit to 3 GB. To find out how to do this, visit www.autodesk.com/support, choose Revit Architecture from the menu, and read the support article on enabling 'The 3 GB switch and Revit'. Of course, you need more than 2 GB of RAM in your workstation for this switch to do you any good.

More information on RAM and virtual memory can be found at the Autodesk knowledge website. Visit this site for details: http.//usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=8018971&linkID=9243099.

As another option, Revit supports 64-bit operating systems like Windows XP 64-bit and Windows Vista. This allows you to tap into even more RAM and go well beyond 3 GB.

A CAD file imported into Revit is a collection of objects that is managed as a single entity. If you explode a CAD file, the single object immediately becomes many — and becomes that much more data that Revit needs to track and coordinate. If you're unfortunate enough to explode a hatch pattern, one object becomes many thousands. If you're importing DWG files, leave them unexploded as much as possible. If you need to hide lines, use the Visibility/Graphic Overrides dialog box to turn layers on and off. Explode only when you need to change the imported geometry, and start with a partial explode. Figure 15.1 shows the tools available in the Options bar when you select an imported or linked DWG file. Also note that lines smaller than 1/32″ are not retained with CAD files that are exploded. This can result in unusable imports.

Figure 15.1. Import and explode options

Another option is to change the DWG file directly in CAD by deleting lines and layers you don't need, then reimporting the file into Revit.

As a final option, if you feel like you need to edit the linework in Revit directly, import your CAD file into a 2D Detail Component family, edit the linework there, and import that Detail Component into your project file. This is a great way to keep the CAD file editable but also keep the number of objects in your project file minimized.

Often, you import a DWG as a reference, but then you don't need it later in the project lifecycle. It's easy to forget, but if you no longer need an import, go ahead and delete it by selecting it in the view, right-clicking it, choosing Select All Instances from the context menu, and deleting it. This will delete the import in all views.

Figure 15.2. Close hidden windows that you're not using

Figure 15.3. Do not compute room volumes unless necessary

Keeping the number of open views to a minimum helps the model's performance. Choose Close Hidden Windows from the View ribbon often (Figure 15.2), because it's easy to have many views open at once, even if you're concentrating on only a few views. Once you reduce your open views to just two or three, you can take advantage of the view switch toggle: press Ctrl+Tab, and you'll cycle through your open views. Press Ctrl+Shift+Tab to reverse the view cycle.

You can turn on room volume calculation by choosing Area and Volume Computations from the Room flyout on the Home ribbon. Check Areas and Volumes under Volume Computations (shown in Figure 15.3) only if you need room tags or a schedule to display volumetric information. Don't forget to switch off this option after you print or view the information. Otherwise, the volumes will recalculate each time you edit something in the model, and this can affect the overall performance of your file dramatically.

Sometimes in a workshared environment, your local copy can begin to perform poorly but others on your team don't share the same problems. If this is the case, we recommend that you make a new local file. Local files can become problematic because of any of the things that commonly cause issues with large files in a networked environment. As a general practice, it's a good idea to make a new local copy once a week.

In the Application Menu → Options → Graphics tab make sure you have both Use OpenGL Hardware Acceleration and Use Overlay Planes to Improve Display Performance checked (Figure 15.4). Deselecting the overlay planes check box can cause significant degradation in performance — we recommend you never deselect this option.

Figure 15.4. Enable video card options for better performance

Figure 15.5. Import into one view

Importing in all views can seriously affect performance. Figure 15.5 shows the Link (Instead of Import) check box in the Import or Link dialog box. Linking is better than importing if you don't need to edit the geometry.

Although Revit has the ability to import files from a number of other sources, you should exercise caution when doing so. If you're importing a 60 MB NURBS-based Rhino file into your model, expect your Revit model to grow in size and react a bit slower than it did before the import. Delete unneeded imports or convert them to Revit content to reduce file size and improve overall performance.

Revit has a built-in tool that allows you to purge unused families and content. This is a good way to reduce file size, improve performance, and minimize the list of things you need to search through when adding content in the project. Loaded but unused families can make your file grow quickly. To purge, choose Purge Unused from the Manage tab. If your file is very large, it may take a few minutes to run this command before you see the dialog box shown in Figure 15.6. Here, you can opt to keep or purge families individually.

Figure 15.6. Use the Purge Unused dialog box to reduce file size

This is typically not a good idea at the beginning of a project, because your template may contain families that you intend to use but haven't yet inserted (such as wall types).

Learn to manage the amount of information needed in your views. Don't show more than you need to show in a view either in depth or in your level of detail. Here are a few easy ways to keep your views opening and printing smoothly:

Shadows can help you make beautiful presentations, give a sense of depth in façades, and show the effect of the sun in a site plan view; however, shadows are performance intensive and can significantly slow a view's time to open, print, or regenerate as you pan and move around in it. Make sure you turn off shadows whenever you don't need them.

One of the benefits of having worksets is that you don't have to turn them all on at once. When you open the project, go to the Workset dialog box. There, you can highlight a workset and click the Close button (see Figure 15.8). Doing so drops that workset from active memory and gives you better performance. Remember, if worksets are closed, you can't do anything with them. If a workset isn't visible, it won't print. To print a current copy of the whole model, you'll need to turn the worksets back on.

Figure 15.8. Worksets can be closed to reduce the amount of memory used to open a file

For larger projects, or campus-style projects, you can break up your model into smaller submodels that are referenced together. You can also do this on a single building. If you decide to divide your project, make your cuts along lines that make sense from a holistic-building standpoint. Don't think of the cuts as you would in CAD, but think about how the actual assemblies will interact in the building. As an example, don't cut between floors 2 and 3 on a multistory building unless you have a significant change in building form or program. Here's a list of some good places to split a model. See Figure 15.9 for an example:

Printing big Revit files can sometimes take a long time. Enabling raster printing speeds up printing, although there is a trade-off compared to the quality that vector printing offers. Depending on the printer, you may get better line quality by going to a DWF or PDF first, then printing your physical sheets. Experiment on a few sheets to see what your printer responds to best before sending your entire set. Printing a digital set first will also give you a record copy of what you have just printed as well as a quick way to make additional copies later if needed.

Figure 15.9. Splitting up a model can improve performance

Don't fall into the trap of overmodeling. Just because you can doesn't mean you should. Be smart about the level of detail you choose to model based on the complexity and size of your project. Some data is just easier and better to show in a 2D detail rather than as 3D model data. The amount of information you model or do not model should be based on your project size and complexity, your time frame, and your comfort level with the software.

Many people who understand the principles of modeling in Revit struggle with the changes in methodology when actually creating a set of construction documents. When moving from modeling to detailing, you will find that you are creating and modifying families to add details specific to the current state of the design. When doing this, it always begs the question, "How much do I model?" As a rule of thumb, here are three simple questions to help you make the right decision:

User-defined relationships and constraints are important to embed in the design to help keep important dimensions constant. However, if you don't need to lock a relationship, don't. Even though the option to lock all alignments is available, it's often not necessary to do so. Overconstraining the model can cause problems later in the project process when you want to move or modify an element and you need to figure out (or remember) what you locked and where to allow the particular element to be moved or modified.

It is possible to create families in Revit with a seemingly infinite amount of detail. Use the Visibility tool found in the Family Editor to set the appropriate level of detail for when the element is viewed in plan, elevation, or section. Setting elements to Coarse, Medium, or Fine can also keep your families from looking like blobs in Coarse view and small scales as well as quicken your screen-refresh times.

If you keep encountering a dialog box telling you the model is overconstrained and this is impeding your workflow, you can delete the constraint. If it is a simple element (such as a wall with no openings or sections), it might be easier to simply delete and redo the troubled object.

To avoid long opening times for really large files, establish an office standard that you always close your last view as a drafting view or legend that is empty, or maybe contains only some text with the project name. This way, when Revit first opens the project it will need much less processing time. By default, Revit always opens with the view from when the project was last saved. We've seen some nice-looking "project pages" made with a drafting view using text and some simple instructions.

Many CAD workflows required you to use the same version of CAD over the lifecycle of the project. So, a project started in CAD 2000 would stay in CAD 2000. With each new release of Revit, many changes have been put in place to make large files easier to manage, to make saving faster, and to improve overall performance.

Auditing the file will review the data structures and correct problems that are found within the model. An audited file won't look any different when the audit is completed; however, it should (ideally) not crash. This is not a cure-all, by any means, but it can help you get out of a tight spot when necessary.

Figure 15.10. The Audit option is located in the Open dialog box

Get everyone out of any worksets and local files, and have them relinquish their permissions. Open the file using application button → Open. The resulting Open dialog box lets you browse to a project location. Select your project and before clicking the Open button to open the file, select the Audit check box in the lower-right corner (shown in Figure 15.10). Revit gives you a warning before performing an audit on your file. The audit itself can take several minutes to complete. When this process is finished, save the project with a new name or in a new file location; don't save this file over the old Revit file. Saving over an existing Revit file can sometimes lead to instability. When you're finished, have everyone make a new local file, and you can get back to work.

Each time you create something that Revit considers a problem, a warning is issued. Warnings will accumulate if left unresolved. Think of all these errors as unresolved calculations. The more there are, the more your computer will have to struggle to resolve them, and eventually you will have performance issues or file instability. Revit provides an interface where you can review all the warnings in the project and fix problems.

Figure 15.11. Review the warnings in this dialog box

Try to read and react to all warnings that Revit sends. You don't have to do it when you're under a tight deadline or when doing so will interrupt your work. But once a week, you should spend 30 minutes reviewing the warnings, as this can improve your model's overall performance. You can find the list of warnings in your file on the Manage tab → Review Warnings (Figure 15.11).

We referred to this earlier in the "Best Practices" section. Purge can also be used to get rid of poorly built families that might be wreaking havoc in your file.

Planning is always a good way to start a project. Regardless of your project, when working with Revit it's always harder to go back and modify the model to fit a new goal than to build to suit the goal along the way. You can set yourself up for a successful implementation from the beginning by using a bit of forethought about your process, workflow, and desired outcome. If you are using Revit for the first time, set some reasonable limits for how far you plan to take the modeling and detail process. This will help guide the development of families along the way. If you are trying to push into some higher-level BIM challenges like 4D, costing, or energy modeling using Revit model geometry, set those goals at the beginning of the project process as each will require you to focus on aspects of the BIM model you might not have typically considered.

As design professionals, we have a tendency to develop unique graphic conventions and styles for our documents. This is a specific area where good planning leads to a good project. If possible, get your standards in place before you begin a project. Revit does an excellent job of getting you started with a good template of graphic standards to work with. However, if you're like most architects, an application right out of the box is never quite nice enough. Revit provides a good starting point for customization, and with some up-front time, you soon can have your project and office standards up and running. Once you nail down your standards, they can be easily applied to your project using Transfer Project Standards.

You're leveraging technology to help you change the way you approach design and documentation. Don't expect the process to have the same workflow as it did in a CAD-based system. Try to stay flexible in your expectations and schedule and allow yourself time to adapt to the change.

There are many advantages to using BIM as a design and documentation methodology. As this process becomes more mainstream within the industry, those benefits will only increase. All of these things and more are possible with the use of Revit, but it will take a couple of projects to get there. Tailor the use of BIM to the project, and use the features that will maximize the benefits of using BIM. Choose your goals realistically based on the expertise of your project team, and plan ahead so those goals can be met successfully. Consider a project that is less complex for your initial pilot.

We can't stress this enough. As you refine your design, it's critical to model correctly right from the beginning, so you don't have to fix things later. What does this mean? As an example, think of a wall. Does it sit on the floor, or does the floor attach to the wall? If you can begin to think about how your project will be assembled, it will save you a lot of time at the end. It's good practice to plan ahead, but remember that Revit will allow you to make major changes at any stage in the process and still maintain coordination. If you are still in the early phase of design and do not know the exact wall type, use generic walls to capture your design intent; changing these later will be simple.

A key advantage of using Revit is the ability to change your project schedule. In a traditional design process, most of the effort on a project is realized during the construction-document phase. At that time, a typical project has the most staff working on the project, and it can be fairly difficult to implement major changes to the project design. This is due to the complexity of the documents by this time and the amount of effort for the team to redraw all the changed information. You'll find that with Revit, design change is largely managed by the software itself. This gives you a great deal of flexibility in both your design and documentation. Take advantage of this shift in the process, and add information to your model early. It can be in the form of more detailed content or showing the material construction of your wall system. Remember that you can change all this information much more quickly and easily than you ever could in CAD, so don't assume you're locked into the information you displayed early in the design process.

Communication within a team is critical for understanding a project and documenting it successfully. One of the downfalls inherent in a CAD-based system is that there is no connection among the different files that make up the drawing set. This phenomenon carries through to the project team and is a function of project workflow and project management. In CAD, it's possible for team members to work in some degree of isolation. They aren't forced to immediately reconcile their changes with changes made by their teammates. Revit's single-file environment forces a much higher degree of team communication between not only the architects but also your structural and mechanical engineers.

Most of us have drafted in a 2D environment until now. Moving to a 3D world is a significant change. Do you have to model every single screw? Every mullion? Every stud? That's a good question. The simple answer is no, you don't have to, and in fact you should not attempt to do so. Like any BIM system, Revit isn't 100 percent 3D information. Standard computer workstations aren't capable of handling all the data of a building in model form. Additionally, few projects have the time in their schedule to model the screws in a sheet of gypsum board or the sealant around all the windows; some of that information is best presented in 2D or in the specifications. This still leaves you with a wide range of options for modeling. In the beginning, err on the side of simplicity. It's far easier to add complexity to your model later on as you gain experience and confidence than it is to troubleshoot overconstrained parameters early in the process. Start with the big ideas: walls, openings, roofs, and so forth. Work your way down to a comfortable level of detail for both you and your computer.

A BIM project team includes three basic technical roles. These roles are interchangeable, especially on smaller projects with fewer team members. However small the team, it's useful to make sure all these roles are filled:

Your first stop, if or when you get stuck, should be the Revit Help menu. It's one of the easier and more robust help menus out there, and it can give you a lot of useful information very quickly. It's also the most accessible help source. As with most applications, it's at the far right of the menu bar.

If you have bought Revit on subscription, Revit Subscription Support offers an exemplary web-based support system. Their responses are speedy, and their advice is top-notch. If you need information more quickly, Revit also has an online knowledge base of FAQs that is available without a subscription. Both of these resources can be accessed at www.autodesk.com/revit.

Autodesk User Group International (AUGI) is also an excellent source for tips and tricks. It's an online user community free to participate in, ask questions, get answers, and share families and examples. To get the benefit of this fantastic online resource, go to www.augi.com and look for Revit Architecture as a product. If you've never logged in, you will have to register once; from then on it's easy!

Looking for content and families? Revit City, another free online service, has a growing database of free families posted by other users. Its address is www.revitcity.com.

These pages offer insightful discussions and some great Q&A threads: http.//discussion.autodesk.com/.

This website is dedicated to following and reporting on the trends in the AEC industry, with a strong focus on BIM, technology, and the direction of the industry — put together by Lachmi Khemlani: www.aecbytes.com.

There are numerous blogs from passionate, experienced Revit aficionados. Here are some of them in no particular order: