Autodesk Revit 6

Welcome to the inaugural issue of the AECbytes Product Review series, which kicks off by looking at the new release of a critical AEC application, Autodesk Revit 6. As discussed in AECbytes Newsletter #2, Revit is Autodesk's purpose-built building information modeling (BIM) solution, and its success will be critical for Autodesk to maintain its leading position in the AEC software space, which it currently holds because of the predominance of AutoCAD.

It has been exactly a year since I attended Autodesk's BIM event and wrote about Building Information Modeling for the first time (see Cadence AEC Tech News #90). In that and succeeding issues, I have analyzed the BIM perspectives of the three leading vendors, Autodesk, Bentley, and Graphisoft. As I pointed out subsequently in Issue #103, the BIM race is still wide open and no one solution has emerged as the clear leader.

At the same time, awareness of BIM among technology leaders is sky-rocketing, as evidenced by the presentations and discussions at the recent AIA Technology in Architectural Practice conference (see Issue #108). I know of several firms who are in the process of evaluating the different BIM solutions to determine which best serves their needs. Some have already started executing pilot projects. A few firms--the early adopters--are much further on in the implementation path and are already realizing some of the significant benefits of the BIM approach.

Thus, the new release of Revit comes at a defining moment in the transition of the AEC industry from CAD to BIM. This review takes a detailed look at what Revit 6 has to offer, and analyzes the strengths and limitations of the product as a whole. For those not familiar with Revit at all, please see my overview of the application in Cadence AEC Tech News #72, written shortly after its acquisition by Autodesk in April 2002.

Summary of Changes

Revit 6 is a major update of the program, with an array of new features and enhancements. Two of these stand out in terms of their overall significance and impact on the design process: the ability to create alternate design schemes inside a single project file; and multi-user element borrowing in worksets, which makes it easier for an extended design team to work concurrently on the same project. Both these features are described in detail in subsequent sections.

Other enhancements in Revit 6 include an overhaul of the stair and railings tools; curved column grids; automatic creation of curtain wall grid divisions; the inclusion of ellipses in the drawing toolset for sketching; plan regions that allow split-levels plans to be correctly displayed; custom organization of the Project Browser; the ability to represent room areas and boundaries by phase; detail views and a new Repeating Detail tool for easier creation of detail drawings; formulas and filters in schedules for common calculations and custom display; a spell checker for checking text notes in views; improved ODBC and DWG export; and the ability to save out families that are loaded in a project. Various minor improvements have also been made in dimensioning, modeling, rendering, and viewing capabilities.

There are two other significant pieces of good news about Revit 6 , which are not related to specific features. One, the speed of save time has been reduced by as much as 30%, according to Autodesk quality assurance tests. For those working on large projects, this will be keenly felt and appreciated. Also, Revit now uses Autodesk's standard licensing system, allowing a firm to conveniently manage its Revit licenses in the same way as all its other Autodesk products.

All these performance enhancements don't come free, however--running Revit 6 may require an upgrade of operating system software. Revit joins the increasing list of AEC applications that don't run on operating systems older than Windows 2000 or Windows NT 4.0 (SP6 or later). The minimum hardware requirements remain the same as in the previous release: Intel Pentium III or AMD Athlon processor, with 256 MB RAM for single-user projects and 512 MB RAM for multi-user projects. Complex Revit projects, however, get heavy on resources, so hardware upgrades might also be required.

Let us now look at some of the key new features of Revit 6 in more detail.

Multiple Design Options

Revit now has the ability to capture multiple design options, which can be used to design and present alternatives for different aspects of a building such as a roof, a structural system, a façade, an entire section of a building, the furniture layout in a space, and so on. A new design option set can be created for each design issue for which alternatives are being explored. A set can comprise several options, each representing one possible alternative to the design problem. Of these options, the main one under consideration is designated as the primary option; it has a closer relationship with the main model and is the one that is visible by default in all views. You can, however, create different views and modify their visibility properties to display the main model with each of the secondary design options. As shown in Figure 1, this allows multiple design options to be created and conveniently displayed for reviews and client presentations. The design options are accurately reflected in schedules as well, facilitating a more comprehensive analysis. Once an alternative has been finalized, it can be accepted as part of the main model and all the other options are automatically deleted.

I found the design options feature, on the whole, fairly simple and straightforward to use. Where it does get somewhat tricky is determining how changes in the main model affect the multiple design options, in light of the fact that only one of the options is visible at a time. Recall that Revit is a fully coordinated building model with a parametric change engine that automatically filters changes to all associated elements to maintain model integrity. I found it very impressive that building elements in all the design options can reference elements in the main model, which means that modifying the main model makes the corresponding changes in all the options while still maintaining the integrity of the building model. This must have involved considerable programming effort and expertise. However, elements in the main model can only reference elements in the primary option and not in any of the secondary options; this does not, for instance, guarantee automatic wall cleanup between a wall in the main model and a secondary option. The Revit documentation gives guidelines to deal with such issues, as well as lists several important considerations that must be kept in mind while working with design options.

Element Borrowing in Worksets

A new feature in Revit 6 that will be greatly appreciated by multi-user design teams using worksets to divide up a large project along themselves is element borrowing. Previously, a design decision by a team member ("User A") that necessitated a change in another user's workset required that user ("User B") to relinquish control of it, so that it could be checked in by User A and then changed. Not only was this disruptive to the workflow, it also required User A to load an entire workset into memory in addition to their own, slowing down performance. With the new element borrowing feature, only those elements that are required for editing from another workset can be borrowed, instead of the whole workset. This speeds up the workflow by avoiding check-in and check-out of worksets, and avoids the slowdown of operations that User A would previously have to suffer.

In brief, this is how element borrowing works: Let's say that both User A and User B are working simultaneously on two separate worksets that are part of the same project. User A selects an element for editing that is in User B's workset, is warned about not having permission to edit the element, and is allowed to place a request to User B for obtaining the necessary permission. User A then needs to contact User B to let them know about the request, at which point User B can grant the editing permission. This element borrowing scenario is illustrated in Figure 2. On the other hand, if the element needed by User A is on a workset that is not checked out by anyone, no permission needs to be obtained; the element can simply be borrowed and edited right away.

The only shortcoming in this otherwise very useful and much needed feature is the lack of automatic notification, in the concurrent use scenario, to User B about a pending request. Instead, team members have to rely on the phone, e-mail, or some external instant messaging system to communicate these requests to each other. For a more seamless workflow, the automatic notification for element borrowing should ideally be built into the application. This is particularly critical given Revit's built-in connectivity between building elements and automatic propogation of changes, which may require users to resort frequently to borrowing elements from other worksets in use when making changes to elements in their own worksets.

Other Key Enhancements

Revit's Project Browser can now be customized and organized by individual users according to their personal taste and to suit the task at hand. In a large project, navigating the lengthy Project Browser listing all the numerous views and sheets can be cumbersome. Revit 6 allows views and sheets to be grouped and subsequently filtered so that only the desired groups are visible in the Project Browser. Groupings can be based on phase, discipline, view type, and so on, and can including secondary groupings and a sorting order. A filter, which can be a project parameter applied to certain views, can then be chosen to limit the number of views that display. An example of a default Project Browser and its subsequent customization is shown in Figure 3.  

Improvements have been made to both the Stairs and Railing tools in Revit 6 . Stairs have several new properties that affect riser and tread geometry and allow more stair conditions to be designed. Stair runs can be modified by dragging the run line to add or subtract risers. Railings can now be designed with more complex baluster patterns and panels. Users have more control and can specify the start, end, and corner conditions as well as a custom pattern for locating the balusters and posts along the railing.

Revit 6 has a new Plan Region command that allows a region to be defined within a floor plan or reflected ceiling plan view with a different view range from the overall view. Plan regions will be useful for displaying split level plans correctly and for displaying inserts above or below the cut plane. Since they only work with plan views, they cannot be used to perform the same functionality in section views. Thus, they cannot fully make up for Revit's inability to jog clipping planes, whether in plan, section, or elevation--a feature that is sometimes needed.

Two enhancements in Revit 6 should make it easier to create detail drawings for construction documents. A new view type called detail view has been created that appears as either a callout or a section in other views. This type of view typically represents the model at finer scales of detail than in the parent view and is used to add more information to specific parts of the model. All detail views are listed in the Project Browser, from where they can be managed. An example of a callout detail view is shown in Figure 4. The new Repeating Detail tool also makes detailing easier in plans and sections. This lets you sketch a path by defining two points, which is then filled in by the selected pattern of detail components such as metal deck, brick, tiles, and so on. A repeating detail can be locked to adjoining model geometry, so that it is automatically adjusted when changes are made.

Main Strengths and Limitations

The biggest strength of Revit is hands-down ease of use, which is particularly commendable given the complexity of most high-end CAD and BIM applications. Despite the addition of new features in every release that add to the size of the application and its complexity under the hood, the basic interface of Revit continues to remain simple, elegant, and intuitive to use. Smart features such as parametric building components, built-in interconnections that intelligently propagate changes to all associated elements, the display of temporary dimensions that can be written over to resize a component while it is being created, the immediate availability of 3D views-all these contribute to a fun and interactive design experience that also provides instant and critical feedback on design decisions.

From a documentation standpoint, the automatic generation and coordination of all views and documents and the instant update of all views when any change is made to the model eliminates inconsistencies and the tedium of manual drafting and checking. Schedules of rooms, doors, windows, and other components can be generated instantly and are always synchronized with the model. All component specification information is captured within the model and is available for analysis, while the phasing tools provide a means to easily make demolition drawings for renovation projects.

Revit still has its share of shortcomings related to specific features that have not yet been addressed in the new release. Its massing tools are awkward and prevent the application from being seriously considered for schematic design, particularly by design principals; its ability to model organic forms are limited; rendering capabilities are not as sophisticated as dedicated 3D visualization programs; and enforced associations between elements sometimes result in undesired changes when modifications are made.

Taking a step back and evaluating the application from a larger BIM perspective, Revit currently has two critical omissions. One, it is primarily an architectural design application and is missing the ability to not just represent, but also design structural, mechanical, electrical, plumbing, and other building systems with the analytic tools needed by these engineering professionals. Two, it is still weak on interoperability, which will be needed for the application to work in an integrated manner with other tools used in building design and construction, both upstream (such as programming, conceptual sketching, or quick 3D massing) and downstream (such as energy analysis, cost estimating, construction scheduling, facilities management, and so on). Improvements have been made in version 6 for ODBC and DWG export, which will facilitate some hooks to other applications. However, unless Revit builds in all the functionality that will be needed for end-to-end building design and construction (a near impossible task), it will need better ways to facilitate interoperability, including an open API (Application Programming Interface) that third-party developers can use, and IFC support, which seems to have become the de facto interoperability standard in the building industry.

And finally, no review of Revit can be written without acknowledging the scalability issue. One of the questions I get asked most frequently about Revit is: "Can it handle large projects yet?" The overall perception in the industry is that Revit is not easily scalable, since all the building information resides in a single file. Yet, there are examples of large projects successfully completed in Revit, such as the one shown in Figure 5. There is no doubt that Revit is resource intensive--all the interconnections between the building elements increase the file size and become increasingly demanding on system resources as the project gets more complex. Thus, high-end workstations would be required to run Revit efficiently, even with the 30% reduction in save time that Revit 6 promises. But as I pointed out earlier, BIM doesn't come cheap, in particular, smart BIM. In the meantime, there are techniques to deal with the scalability issue, a key one being worksets and the new element borrowing capability. Model linking is another technique suitable for separate buildings on a large site. Other techniques are purging unused elements, and finding appropriate substitutions for complex geometry. What is needed is for these and other techniques to be compiled into a document that can provide guidance to users on how to keep the file size of a project within manageable limits.

Conclusions

Autodesk Revit 6 includes several new features and useful enhancements, and for firms who are seriously implementing it, the upgrade should be worth it just for the design options and element borrowing capability alone. The reduction in save time and the overhaul of the licensing system will be greatly appreciated as well.

Overall, Revit is a superior application for architectural design development and documentation, particularly notable for many built-in smarts and ease of use, as well as its ability to automatically produce accurate and fully coordinated documentation. Where it currently falls short is in its capability of being seamlessly integrated with the larger suite of building design, construction, and maintenance tools needed for full building information modeling and lifecycle management. Considering that BIM is still in its early days, most architectural firms can reap the numerous benefits of Revit right away as they transition from CAD to BIM, and Revit's ease of use can certainly help to make the transition easier. However, in the long run, the large-scale acceptance of the software as a leading BIM application will depend on Autodesk's ability to define and present a clear strategy of how it can be a well-fitting part of a larger whole.

About the Author

Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and consults and writes on AEC technology. She can be reached at lachmi@aecbytes.com.

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