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AECbytes Product Review (July 26, 2006)

Autodesk Revit Building 9

Product Summary

Autodesk Revit Building 9 is the latest version of Autodesk's leading BIM application for architectural design that integrates elements, views, and annotations into a single, coordinated building information model.

Pros: Ease of use remains unmatched, despite the continued addition of features enhancing the power and sophistication of the application; critical improvements in the generation of construction documents, including keynoting and an expanded Detail Library; rooms are now actual Revit elements, allowing better integration with tools needing spatial and volume information; improved interoperability with SketchUp and enhanced IFC support; API expanded to provide access to more Revit functionality, making it easier for plug-in tools to be developed; several other enhancements including animated sun studies, material take-off schedules, user-defined filters to control visibility, and improvements in linked files.

Cons: The quality of documentation continues to remain substandard, making it difficult to learn the application without outside help; not sufficiently fluid for conceptual design; non-regular building forms are difficult to model; the room element is problematic in some aspects and needs further development; still allows some illegal operations to be performed, which can undermine the integrity of the model.

Price: Suggested retail price for the standalone (non network) version of Revit Building 9 is $4995; for AutoCAD Revit Series 9, a bundle of AutoCAD 2007 and Revit Building 9, it is $5395.

Earlier this year, Autodesk's Revit platform officially became a complete BIM solution for supporting collaborative multi-disciplinary building design, with the introduction of Autodesk Revit Systems for MEP engineering. At the same time, Autodesk also released updated versions of its Revit Building and Revit Structure applications for architectural design and structural engineering respectively. Revit can now realize the full potential of BIM in enabling cross-disciplinary collaboration, with architects, structural engineers, and MEP engineers using the same building model and the same modeling tools for building design. AECbytes will review all three products over the course of the coming months, starting with Revit Building 9 in this issue.

To get a historical perspective on Revit's evolution, please see my reviews of Revit Building 8/8.1, and of Revit 7 and Revit 6 from the days when Revit was still a single application rather than a platform of multiple products.

Introducing a New Revit Element: Room

One of the biggest changes from an architectural modeling perspective in Revit Building 9 is that a room is now an actual Revit element as opposed to just an annotation as it was in previous versions of Revit Building. This means that you can now create a room in Revit independently of its room tag, although you would invariably add the tag for easier identification if you wanted to generate a room schedule. To create a room, you would typically use the new Room tool in plan view to place a room inside a set of bounding elements such as walls, curtain systems, or room separation lines. By adjusting the Visibility settings of the view, the room can be displayed in an interior fill, as shown in Figure 1. You can also place a room in a free space or one that is not entirely bounded, and then draw room-bounding elements around the room later. By default, the room tag is automatically placed along with the room, but you can choose to deselect this option. It is also possible to create a set of rooms first in a schedule that capture the requirements of the building program, and then place the predefined rooms in the drawing area by select them from the Room drop-down list on the Options Bar. Once rooms are placed, they can be used to create color-coded plans as well as detailed room schedules, as in previous versions of Revit Building.

So what can you do with room elements now that you could not do with just room tags in earlier versions? To start with, rooms can now be graphically displayed with an interior fill and tagged, both in plan as well as section views. It is possible to create rooms that span multiple floors, such as atriums, elevator cores, and so on, as shown in Figure 1, without having them appear multiple times in the schedule. Rooms now have a specific location in relation to other rooms and elements, and their volume can be accurately derived, all of which is critical information for applications such as energy analysis, as well as for integration with MEP applications such as Revit Systems. Over and above this, the new approach makes room elements much more consistent with all other building elements in Revit, which have a physical representation that is distinct from their annotations, and whose properties are attached to the elements themselves rather than to their annotations.


Figure 1. A simple project with offices and a lobby spanning multiple levels, showing the new Room element in plan and section views as well as the Room Schedule that was derived.

While the introduction of rooms as elements is undoubtedly useful, the implementation of this concept in Revit Building 9 could do with some improvements. The biggest problem is that when a room is created, while its horizontal boundaries are automatically detected and are used to define its horizontal footprint, its vertical footprint is not automatically detected by elements such slabs and roofs and is not clearly demarcated. The height of a room is specified using a combination of a level and an offset from that level, irrespective of the presence of elements such as floor and roof slabs. This makes it possible to create a room that span multiple levels of a building even when they are divided by floor slabs, which is clearly incorrect. When the volume of the room is calculated, however, it does take into account room-bounding elements such as floor and roof slabs if they exist below the specified height and it provides the correct volume calculation. The confusion is further complicated by the fact that the graphical display of a room in section views is only a symbolic rectangular representation that does not show the actual boundaries such as sloping walls and roofs, as shown in Figure 1. And room volumes cannot be seen in 3D views at all.

The Room Tag tool—which was the only tool for rooms in previous versions of Revit—continues to exist in Revit Building 9 as a separate tool, which is confusing as well as inconsistent, given that there is no independent Door Tag tool, Wall Tag tool, and so on. Room tags should now be treated as any other tags and should be operated by the general Tag tool, with deals with all other building element annotations.

Other Design and Modeling Enhancements

In addition to rooms, Revit Building 9 includes several other modeling enhancements. On the massing front, the Wall by Face command, which is used to create walls from the faces of a massing model, can now be used in Elevation view. The Sweep operation has been enhanced so that the path for planar sweeps and sweep profiles can now contain arcs, ellipses, or splines, allowing greater flexibility in creating non-regular massing models that can subsequently be mapped to real-world building elements such as roofs, curtain walls, floors, and walls. Another improvement is in the creation of roof elements from the faces of a massing model. When a roof element created with the Roof by Face command is selected, shape handles are now displayed, allowing the side surfaces to be dragged to create roof extensions easily.

Moving on to detailed building modeling, columns can now be attached to roofs, floors, ceilings, reference planes, structural framing members, and other reference levels, either through their top or base, by setting the appropriate options in the Options Bar. They will be trimmed or extended accordingly. Crossing walls automatically clean up using join geometry, and layer routing has been improved for wall joins when more than 3 walls are present. Beams can now be sloped so that all other members joined to it also slope accordingly. Foundation slabs can be defined in the same way as all other structural slabs, making it easier to model mat foundations as well as irregular foundations. There are two new modes for placing work plane-based or face-based components—Place on Face and Place on Vertical Face—in addition to the Place on Work Plane mode available in previous versions. Another work plane related enhancement is the ability to quickly relocate an element to a different host using the Rehost tool, which lets you specify a new work plane and set the new position and orientation of the rehosted element. So, for example, you could quickly move a window from one wall to another wall using the Rehost option. Also, a new family template is provided that allows you to create families that can make complex cuts in the host, and that can be placed on any surface, regardless of its orientation.

A big design improvement in Revit Building 9 is the ability to create and visualize an animated solar study, which is a series of frames showing shadow movement over a defined period of time. In previous versions, only a single frame showing shadow patterns for a specific date and time could be created. For the animated solar study, you can either choose the Single-Day option, which shows the movement of shadows at the project location during a defined range of time on a specific day, or the Multi-Day option, which produces an animation showing the impact of shadows at the project location at a specific time of day over a defined range of days. Some of the frames from a Single-Day animated solar study of a sample project are shown in Figure 2. Such animated solar studies are useful to evaluate the impact of natural light and shadows on the buildings and site, as well as to study the lighting inside a building during specific times of the day and year. Once created, they can be exported as AVI files for easy distribution and viewing by colleagues and clients.


Figure 2. The first six frames of a seven-frame animated single-day solar study of a sample project. The frames were set to a 1 hour interval.

While Revit does not offer a complete cost estimation capability yet, a new feature in Revit Building 9 moves it one step closer to this goal. This is the Material takeoffs view type, which lets you quantify materials used in most Revit Building elements, including paint. Similar to the process of creating schedules for other building elements, Material takeoff schedules can display material properties, areas, and volumes for a single category or multiple categories (see Figure 3). Other new related capabilities are being able to specify identity parameters and user-defined parameters for materials which can subsequently appear in the Material takeoff schedule, as well as the ability to add material tags to the materials seen on faces of model elements and in layers of host elements. In essence, material information is now exposed in a Revit model, and it can be accessed using ODBC or through the API for developing more accurate cost estimation applications that will work with Revit.


Figure 3. A material takeoff schedule for a project, showing the areas and total cost of interior Gypsum Wall Board finishes.

Improvements in Creating Construction Documents

In this release of Revit Building, construction documents are the focus of several key improvements, starting with keynoting. In previous versions, keynotes had to be added to drawings as text, but Revit Building 9 features a comprehensive keynoting utility, which includes a new Keynote type parameter for all model elements and detail components, an external keynote table file in TXT format that captures key values and corresponding text for keynoting, and keynote legends that are a new type of schedule displaying key values and keynote text. The sample text file for keynoting that is provided is based upon the 1995 CSI Master format system, widely used in the US, which uses 16 divisions to organize construction process and materials. This file can be modified by a firm to incorporate its own keynoting system. Keynote values can be assigned to materials and element types in advance through the Materials dialog and the Element Properties dialog respectively. Subsequently, the Keynote tool can be used to add keynote tag to materials and elements in the drawing (see Figure 4-a). If no keynote value has been assigned in advance, the Keynotes dialog opens up, allowing you to select a value (see Figure 4-b). It is also possible to specify "user keynotes" for commonly used notes or phrases to address documentation issues; however, these are not part of the sample Revit keynote file and have to be separately added. Once all the keynotes have been added, keynote legends can be created for a specific sheet, displaying only those keynotes that are visible in views on that sheet, or for the whole project, in which case they can be grouped according to the CSI division headings.


Figure 4. (a) Keynotes added to a detail drawing. (b) Browsing through the keynote table file, which is organized according to the CSI Master format system, to assign a keynote to an element.

In addition to keynoting, the detailing capability has been enhanced by the addition of over 500 new 2D detail components to the Revit Detail Library, organized in directories by CSI division. Other documentation related enhancements include the ability to save drafting views, schedule views, and sheets with drafting views as new files for reuse in other projects; the ability to save 2D and annotation information added to a live Revit Building detail to a new RVT file for reuse in other views or projects; a new Show Hidden Lines tool for displaying obscured lines of detail elements fully or partially hidden by others; easier dimensioning of non-orthogonal intersecting walls; and several improvements related to tags including tags for detail components, easy toggling of a tag between horizontal and vertical orientations by using the Spacebar, selection of multiple tag categories for the Tag All Not Tagged tool, and tag leaders with free ends that allows them to be placed on any point of the tagged element.

Another useful new feature is the ability to create user-defined filters to override the graphic appearance and visibility of all elements that share common properties in a particular view. For example, if you needed to change the line style and color for different fire rated walls, you could create separate filters for the different walls based on fire rating. The necessary changes can then be applied to all the walls with that fire rating property. Figure 5 shows an example where three different filters have been defined for three different fire rated walls, which are then used to differentiate the walls with different colors in a floor plan.


Figure 5. Defining separate colors for walls with different fire ratings in a floor plan. The filters for the three different wall types based on fire rating had been previously defined.

Interoperability and Workflow Improvements

Rounding up the list of enhancements in Revit Building 9 are those related to workflow and better interoperability with other applications. Topping this list in terms of popular demand is the ability to directly import SketchUp (SKP) files into a Revit Building mass or in-place family. While some SketchUp objects and properties cannot be imported and issues such as two-sided surfaces and scaling have to be resolved, the new capability is best used for creating a massing model in SketchUp and then using the Building Maker capability in Revit Building to transform the mass into building elements (see Figure 6). Other notable import/export improvements are the ability to import 3D room volumes—thanks to the introduction of the new Room element—to the gbXML format for energy analysis with Green Building Studio; support for the 2007 DWG and 2007 DXF formats; more export layers and merging of collinear lines when exporting to DWG; more options for linetype scaling in DWG/DXF exports; the ability to export object data to 2D DWF files in addition to 3D DWF; and support for Autodesk i-drop, which allows i-drop objects from an i-drop enabled web page to simply be dragged and dropped into Revit. (But note that i-drop objects are purely geometric at this point, not intelligent building objects.)


Figure 6. Importing a SketchUp model (this one was downloaded from Google's 3D Warehouse), shown at the top, into Revit Building as a massing model, which can now be converted to a building model using Building Maker.

Revit Building 9 now supports the latest version of the IFC 2x2 data exchange standard, of which the IFC 2x2 export from Revit Building has received full certification by the International Alliance for Interoperability (IAI). You can also import an IFC file into Revit. However, this ability does not mean that Revit can now seamlessly interoperate with other IFC compliant BIM applications, as all of them have different ways of creating, organizing, and representing information. Revit, in particular, has strong rules about how elements come together to ensure consistency of the model, and unless the authoring application of the IFC file follows the same rules, it cannot be imported into Revit without making some fixes such as deleting problematic elements and resolving overlaps. Therefore, unless all the BIM applications that wish to be interoperable with other applications follow some standard guidelines on how elements are created and located with respect to each other, we cannot expect a seamless exchange between BIM applications, even if they are all independently IFC compliant. The IFC capability, in general, is more useful for developing downstream analysis applications that can work with the models created in BIM applications, for example, as demonstrated in CORENET e-PlanCheck, Singapore's Automated Code Checking System. Thus, at least for now, Revit's IFC export capability is going to be more critical than its import capability.

For multi-user and multi-disciplinary workflow, there are important enhancements in Revit Building 9 along two fronts. Linked files have been substantially overhauled with several new options to control the visibility of elements. For example, the display of multiple instances of the same linked file can be controlled together or individually; design options can be selected from the linked file; DWG links and imports now display in the host; you have control of all categories and sub-categories from the linked file; and you can specify whether the linked file should display exactly as it appeared in the native Revit Building file, or whether it should adopt the visibility settings of the host file. Another new feature is the ability to query the properties of elements in the linked files by using the TAB key to cycle through and select individual elements inside the linked file for viewing. The Coordination Monitor, which can be used to integrate the different disciplinary models created in Revit Building, Revit Structure, and Revit Systems, has been enhanced so that modifications to walls, floors, and slabs can be monitored in addition to grids, columns, and levels.

And finally, the API (Application Programming Interface) of Revit Building has been enhanced to allow some new operations in addition to accessing elements, extracting geometry, and querying and changing element properties. The API can now also be used to create walls, slabs, grids, and levels; generate dimensions; create all family based elements; create views and sheets; and place views on sheets. This means that third-party applications can be developed that not only work passively with Revit content but can also actively modify some of it. I have already written about one such application in detail, Visual Estimating by Innovaya, that uses the Revit API to automate quantity takeoff and estimating for a Revit model using the Sage Timberline Estimating software engine (see the article, "Visual Estimating: Extending BIM to Construction"). Another example of a third party tool for Revit is a building shadow calculator developed in Japan by GSA, Inc. using the API. Given a building design on a specific site location, this tool calculates and displays the shadows that will be cast by the building at one hour intervals from sunrise to sunset (see Figure 7), which can then be used to guide various design decisions related to building orientation, location, envelope design, fenestration, and so on.


Figure 7. The Building Shadow Calculator plug-in to Revit Building, developed for Japan using the API. (Courtesy: GSA, Inc.)

Analysis and Conclusions

Revit Building 9 features a solid set of improvements and upgrades in all the key areas of the application: design, modeling, documentation, workflow, and interoperability. Now that Revit will be following an annual release cycle that synchronizes with that of the AutoCAD family of products, it gives Autodesk the opportunity to engineer a steady set of improvements every year that will continue to add to the power, sophistication, and usability of the application. Even today, Revit's ease of use remains unmatched. It is the only BIM application where you can get in and start modeling without needing to refer to the documentation. Of course, you cannot get too far without learning the intricacies of the application, but at least, you can make a decent start without having to go through an extensive training session. And established users will greatly appreciate the new features including the ability to import SketchUp files directly, animated solar studies, material takeoff, keynoting, detailing, improvements in linked files, and the multitude of other enhancements. In particular, a lot of effort has been made to improve Revit's ability to generate construction documents, so that users do not have to fall back on using AutoCAD or any other drafting application at the drawing production phase.

The increased capability of working with the application using the API is going to be very critical in developing supporting applications that work with Revit. As I mentioned in my recent article on the AIA National Convention and Expo, BIM is going to spawn a whole new generation of "supporting technologies," which will extend its capabilities to cover many different aspects of building planning, design, and construction. I believe that the ultimate success of a BIM platform will be measured in terms of how large its "ecosystem" of supporting applications is. From that perspective, opening up the application through the API is essential, and it is important for Revit to develop this further in every release.

While the introduction of rooms as a new Revit element type is a significant development, making the application more consistent and bringing benefits such as volume calculation and the spanning of multiple levels, it is still not fully developed, as I pointed out earlier. And Revit is actually not alone when it comes to problems with this particular element. Even ArchiCAD deals with rooms in a similar fashion—you have to explicitly create them as "zones" inside enclosures and have to do some manipulations to ensure that the zone is consistent with the actual volume created by the enclosures. And in the last version of Bentley Architecture that I reviewed, spaces were even less well-developed. In my opinion, all the BIM applications need to rethink how they deal with spaces/rooms; none of them have quite got it right yet. Ideally, the very existence of walls should automatically define some kind of volume, whether fully or partially enclosed, and the application should be smart enough to determine when a space has been created. The user should not have to go through the additional step of explicitly creating and placing a room element within a set of walls, as this subsequently creates problems such as keeping the room element synchronized with the surrounding volume, and other problems that I pointed out earlier in the section on rooms.

Another potential area of improvement for Revit is flexibility in modeling non-regular building forms. For example, you cannot simply select a wall in Revit and incline it—you would first have to create the non-regular form as a mass and subsequently apply the Building Maker functionality to convert the mass into walls, roofs, and so on. And while Revit's massing module is functional, it is far from the ease of use of say, a conceptual design application like SketchUp.

In my last review of Revit, I had pointed out some illegal operations that Revit allows such as overlapping doors and windows, moving furniture into walls and elevators out of their cores, and so on, which do not guarantee 100% integrity of the model. Errors such as these have to be detected by interference checking. I found that most of these problems still persist in this release. While the overlap problem has been fixed for windows, it still exists for doors. Another potential area for improvement in modeling is in the use of the Wall tool. While crossing walls now clean properly, overlapping walls do not. This means that you cannot simply using the Rectangle option of the Wall tool in Revit to quickly create a set of rectangular spaces—you are forced to use the Line option of the Wall tool so that you create non-overlapping walls.

One other aspect of Revit that I have repeatedly criticized in past reviews is the poor quality of its documentation, which forces users to rely on professional help for learning the program. That limitation has only been very marginally addressed in this release with the introduction of a new component in the Help section called the Project Cycle Navigator. This is an animated interface that includes links to various topics organized in categories such as New Features, Essential Concepts, Pre-Design and Planning, Preliminary Design, Design Development, and so on (see Figure 8). While some of the links simply point to sections in the regular documentation, some of them lead to especially prepared slideshows comprising text, images, and occasionally, animations to explain how a feature works. I found that while the Project Cycle Navigator was slick and jazzy in appearance, it wasn't that useful for learning to use the application. The animations are scrunched up in a relatively small area of the screen, making them hard to see. Moreover, they are relatively smaller in number, so that for learning the nuts and bolts of the application, you have no choice but to fall back to the main Help documentation, which continues to have an overabundance of text that is not sufficiently illustrated. And while the Project Cycle Navigator links to the main Help documentation, the reverse is not true; there is no indication if there is an animation related to a specific topic in the Help documentation, let alone being able to access it from there. All in all, attempting to learn Revit by relying on its documentation alone is a very frustrating experience. I hope some serious effort is made to address this problem in future releases. BIM, in general, is complex, and the availability of good built-in learning tools would greatly help to speed up BIM implementation.


Figure 8. Two snapshots of the Project Cycle Navigator. The top image shows one of the opening screens, while the lower image shows the Building Maker functionality being demonstrated in a slideshow.

In conclusion, Revit Building continues to make steady progress in its development as a BIM application, with a useful set of new features and enhancements in this release. It still has scope for improvement along several fronts, but these in no way undermine the inherently high quality of the application. After all, we as an industry have barely begun with BIM, which means that we will continue to demand more and more from our BIM applications and our wish-list will probably keep getting longer and longer. Revit has done very well until now, and if Autodesk continues to invest in its development as it has been doing so far, its long-term success is more or less guaranteed.

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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