AECbytes Product Review (December 15, 2004)
Autodesk Revit 7
Autodesk Revit is a parametric building modeler for architectural design that integrates views, annotations, and components into a fully coordinated and always consistent building information model. It is one of the leading BIM solutions available today.
Pros:Clean, uncluttered interface; basic features easy to learn and use; automatic generation of all needed 2D and 3D views and schedules; powerful change management engine which intelligently propagates all changes and keeps all graphical and tabular views perfectly synchronized; several useful enhancements in the new release.
Cons: Not sufficiently abstract and fluid for conceptual design; current repertoire limited to architectural design (but soon to be addressed by Revit Structure and Revit Systems); no API or IFC support yet for customization and interoperability (but again, IFC support coming soon); overall complexity is increasing; poor documentation of new features and lack of video-based tutorials adds to the learning curve.
Price:Suggested retail price is $4495; regular upgrade price from versions 4.5 to 6.1 is $895, but is currently on promotion for $695.
The new release of Autodesk's purpose-built BIM solution, Revit 7, was formally launched at Autodesk University two weeks ago (see AECbytes Newsletter #16 for an overview of the event). The previous major release of Revit, version 6, at the end of 2003 came at a time when BIM was still being talked about more than it was being implemented. Only a few early adopters were implementing BIM seriously and realizing its benefits; most other firms were still in the process of evaluating different BIM solutions to determine which best served their needs and what the transition to it would involve. That is why when I reviewed Revit 6, I pointed out that its release was coming at a defining moment in the transition of the AEC industry from CAD to BIM, and that its success would be critical for Autodesk to maintain its leading position in the AEC software space, achieved by virtue of the long-standing predominance of AutoCAD among AEC professionals.
Quite a lot has changed in a span of less than a year. The notion of BIM has permeated much deeper into the AEC industry, and the discussions around it are no longer focused on the technology itself and its benefits but on the best means to implement it. It is now being unanimously accepted by AEC professionals that this is the future direction of the industry, and efforts are ramping up to identify and remove the obstacles to BIM implementation. The leading BIM software vendors have many more examples of BIM implementation by firms on real-world projects to showcase. In the case of Revit, the most high-profile of these has been the Freedom Tower project on the site of the World Trade Center, designed by Skidmore, Owings & Merrill LLP (SOM) which was extensively showcased at Autodesk
University. (See AECbytes Viewpoint #7 by James Vandezande, CAD Manager at SOM.) This level of awareness and acceptance allows vendors to spend less time on marketing the concept of BIM to the industry and spend more time and resources on improving their BIM solutions. Let's see how well Autodesk has used its development resources in this new release of Revit.
For those not very familiar with Revit, please see my overview of the application in Cadence AEC Tech News #72, and my subsequent review of Revit 6 in AECbytes.
Better Support for Conceptual Design
Revit 7 has improved its support for conceptual design by including the ability to create building components such as floors, roofs, walls, and curtain wall systems directly from a conceptual massing model. Dubbed as "Revit Building Maker," this new feature is demonstrated by the simple example shown in Figure 1. Looking at the three windows in the top row, the left window shows the massing model only; the middle window shows the massing model with floor faces created at the specified level heights; and the right window shows the building model with floors at different levels, roof, walls along the sides and back, and a curtain wall system along the curved front of the building. All these components were derived simply by selecting the corresponding face of the massing model. A preliminary floor schedule can now be created with the gross floor areas at each level and the total area, as shown in the lower right window in Figure 1. If a change is made to the massing model, the associated building components can be individually updated by applying a Remake command to them so that they continue to remain aligned with the massing model.
Figure 1. A simple example of the use of the new Building Maker functionality in Revit, showing a building model derived from a massing model. The top three windows are 3D views, while the lower windows show the plan at Level 3, a section, and the floor schedule.
While the new Building Maker feature certainly strengthens the link between exploratory massing and design development, the massing tools themselves remain the same (except for sporting an easier-to-use interface)-they allow for the creation of solid extrusions, revolved shapes, blended shapes, and sweeps, in both solid mode for adding masses and void mode for subtracting masses. They also have the ability to push and pull faces for easy manipulation. They are, however, not as flexible as similar tools in traditional (non-BIM) 3D modeling applications, which makes them difficult to use for conceptualizing freeform and unconventional shapes. For instance, the Sweep tool doesn't allow paths with ellipse or spline segments or profiles with non-straight lines, and is thereby quite limited in its functionality. This limitation is somewhat circumvented by a new ACIS solid import feature that allows you to bring a solid form created in another modeling application into Revit and then apply the Building Maker functionality to convert it into a building model. Some standard forms such as box, cone, arch, barrel vault, gable, and so on are conveniently available in a library and can save on modeling time and effort when used.
Revit 7 includes a number of enhancements to improve the ease and flexibility of modeling. A new stacked wall type has been introduced to model walls where the wall type and/or thickness change at different building heights. It is essentially one main wall comprising several different subwalls stacked on top of each other. These subwalls can also be scheduled for quantity takeoffs. Figure 2 shows how a stacked wall is defined, along with an actual instance of this wall type in a project and its corresponding schedule.
Figure 2 The new stacked wall type in Revit 7. (a) shows the wall defined with three subwalls, (b) shows an instance of the wall placed in a project, and (c) shows the wall schedule for quantity take-offs.
There are several other enhancements related to walls. A new toolbar associated with the Wall tool provides the flexibility to directly model walls, convert linework to walls, or convert faces to a wall. A new Radius option allows automatic fillet of walls and linework. You can now embed a wall or curtain wall into another wall, as shown in the example in Figure 3-a, without having to edit the host's wall profile, cut a hole in it, and then add a wall inside that hole. A new graphical curtain grid layout tool supports both regular and irregular spacing, and the shape of mullions can now be customized by the ability to create custom profiles.
The structural modeling capabilities of Revit have been overhauled with new tools such as joist systems, beam setback controls, brace controls, and column-grid attachments. A useful new feature for site modeling is the ability to ability to define subregions on a topographic surface without splitting it up into multiple surfaces. As shown in Figure 3-b, different materials can be assigned to these subregions depending upon what they represent, and their individual areas can be reported in a schedule.
Figure 3.Other modeling enhancements in version 7. (a) Embedding a curtain wall into a wall does not require the host wall to be cut. (b Subregions can now be created on a topographic surface without splitting it.
Parametric Modular Design or Groups in Revit are a powerful feature that allow you to select an element or multiple elements or other groups and then combine them so that they can be modified as one large element. Grouped items maintain their intelligent behavior such as joins between walls, floors, etc., constraint relationships to other elements in the model, and sequential annotation numbering. In Revit 7, groups have been enhanced to provide better support for repeating units, very useful in building types such as apartments, hotels, offices, and so on. Figure 4 shows an example of the interior layout of a hotel room which was grouped and subsequently placed in other rooms. A single instance of the group was then edited-the desk and chair were rotated to face the exterior wall. The change was automatically made to all the other group instances as well.
Figure 4. The Groups functionality has been enhanced in Revit 7 to provide better support for repeating units, such as the ones shown here. A change made to one instance is automatically updated in all the other instances.
Revit Parametric Components is the term for Revit's open graphical interface that allows the creation of custom parametric content in families without having to know a programming language. Families are the backbone of the application; everything you create belongs to some kind of family. A large number of families come pre-installed with the application; others can be downloaded from manufacturers' websites and other electronic content catalogs. Custom components can also be created using a special interface known as the Family Editor. A critical new feature in Revit 7 is the ability to create nested families with interchangable subcomponents using parametric controls. This makes it possible, for example, to create a door family within which multiple transom types are nested. Once this family is loaded into the project, the transom component can be swapped with the type that is required. Other useful enhancements are the ability to add reference lines to control more complex geometry and parametrically control angular dimensions within the Family Editor, and the facility to create work plane-based families that are hosted by the active work plane when loaded into a project or nested with another family.
Improvements in Presentation, Visualization, and Documentation
Some new features along the presentation front will be greatly appreciated by architects. Revit now features shadow casting in both 3D and 2D model views, even if they are non-rendered. The shadow and sun intensity can be varied, and the sun settings for the shadows can also be defined as required. Another enhancement is the ability to apply silhouette edges in views. Figure 5-a shows how the presentation quality of an elevation has been greatly enhanced with shadows and silhouette edges.
Also new is the ability to create section boxes for perspective views that cut model geometry and cap off faces of the cut geometry. Thus, you can now create sectional perspectives in Revit complete with shadows, capped section boxes, and silhouette edges, as shown in Figure 5-b, which can be very useful in explaining design intent.
Figure 5.Presentation capability in Revit 7 has been enhanced by the ability to display shadows and silhouette edges in non-rendered 2D views, as shown in (a), and the ability to create sectional perspectives, as shown in (b).
While the visualization capabilities within Revit itself, powered by Accurender, remain unchanged, it is now possible to export a Revit model in 3D DWG format to Autodesk VIZ 2005 via a plug-in (called the Autodesk VIZ 2005 Interoperability for Revit Plug-in) for generating highly photorealistic images and animations. The materials and views defined in Revit are maintained in the export, which will eliminate the duplicated effort of defining the same settings in VIZ. Revit 7 also supports version 3.0 of RPC content from Archvision, which can add more realism to native renderings.
On the drafting and documentation front, revisions allow for better tracking of changes and the issuing of construction documents. Revision clouds now understand what revision they are and can be documented with revision tags to display their revision number, as shown in Figure 6. Revisions can be numbered either by project or by sheet. The title blocks in Revit 7 can now have the revision tables in their template. A global revision table can be created, listing all the revisions in the current project. You can also create revision schedules for individual sheets that display all the revisions appearing in it. Once the revision is issued, the cloud is locked down and can then be hidden.
Revit 7 introduces a new Legend view type that allows legend symbols to be created without adding additional elements to a project. Any model, annotation, or system family element can be displayed in a legend. Also, a single legend view can be placed on multiple sheets. These legends are associative and ensure that the graphic symbol display remains coordinated even when the design is changed.
Figure 6 .Revisions can be associated with revision tags in Revit 7 to display the number of the revision.
Other Improvements and What's Coming
Revit 7 introduces new view controls at the bottom left of each view window, as shown in Figure 6, for convenient adjustment of various display settings such as viewing scale, level of detail, shading, and so on. Sections can be segmented, providing the ability to create "jogged" section views showing different parts of the model. Like reference sections and callouts, you can now have reference elevations. The appearance of schedules such as the floor and wall schedules shown in Figures 1 and 2 respectively can be better controlled with properties ranging from title and column headers to gridlines.
Design Options, which was one of the main new features introduced in version 6, has a few enhancements. A design option can now be set current for editing by simply selecting the appropriate design element. Also, when a design option is deleted, the user is notified of the associated views that are affected.
Several import and export options have been improved. You can now export shared parameters such as design options, project information, room information, and phasing to ODBC databases. In DWG and DXF export, identical Revit instances in a view will be written as instances of the same block. They will also be written as instances of the same cell definition when exporting to MicroStation's DGN format. For DWG file import, new functionality includes layer query and partial explode as well as the ability to orient imported DWG files to Revit views. The new ability to import 3D solid geometry, as mentioned in the first section, allows for better integration with other tools and workflows.
On the installation front, Revit 7 now supports distributed and redundant network license server configurations, allowing for more flexible licensing, particularly across multiple locations of the same office.
With regard to what's coming, as I mentioned in my write-up on Autodesk University, Autodesk is soon set to release Revit Structure, the application for structural engineering built on the Revit platform. This will allow structural engineers to create an integrated physical and analytical model of a structure in Revit and have a bi-directional link with external structural applications from vendors such as CSI and RISA for detailed analysis and optimization. Also in the works is Revit Systems, an application for MEP engineering.
Thus, Autodesk is expanding the scope of Revit from architectural design alone to a platform that can support collaborative multi-disciplinary building design, thereby addressing what has been one of its biggest limitations so far. Once the structural and MEP applications are released and implemented, Revit can realize the full potential of BIM in enabling cross-disciplinary collaboration, with architects and engineering using the same building model and the same modeling tool for building design.
Strengths and Limitations
Autodesk Revit 7 continues to build upon the core strengths of the application I had highlighted in my review of Revit 6: relative ease of use, particularly in comparison with other BIM applications; automatic generation and coordination of all views and documents and the instant update of all views when any change is made to the model; parametric building components; built-in associativity that intelligently propagates changes to all associated elements; the ability to define custom relationships between 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 that provides instant and critical feedback on design decisions and helps expedite client approvals; and the ability to automate many tasks related to drawing setup and coordination. Overall, the use of Revit, in contrast to a CAD application, eliminates tedious and redundant grunt work, allowing for more time to be spent on design, and is a much more fun experience.
As I pointed out in the previous section, the upcoming Revit structural and MEP applications will overcome the current limitation of the application scope being restricted to architectural design alone. Autodesk is also making some effort to address the other main limitation of Revit I had pointed out in my review of version 6: weak interoperability. Revit Structure demonstrates the start of an API (Application Programming Interface), which may eventually be expanded to the entire Revit platform. According to Autodesk executives, IFC support is forthcoming as well. Revit has already demonstrated some integration with third-party applications: it can export a gbXML file that can be read into Green Building Studio for performing a DOE-2 energy simulation; there is also e-SPECS, which integrates with Revit through ODBC export to automatically create and update project specifications. One of the key advantages of a BIM application is its ability to support analysis and evaluation tools, and we should expect to see more third-party analysis applications that work with Revit as it evolves.
On the downside, Revit continues to have its share of shortcomings related to specific features that have not yet been addressed in the new release. Its massing tools, as I pointed out in the first section, are still awkward to use and prevent the application from being a serious contender for the conceptual design phase; its ability to model organic forms is limited; its native rendering capabilities are far short of the sophisticated renderings that dedicated 3D visualization programs can produce and do not even match up to the rendering capabilities of some competing BIM applications; and enforced associations between elements sometimes result in cryptic error messages and undesired changes when modifications are made.
I also found that while the basic modeling capabilities of Revit continue to remain unsurpassed in their ease of use, the application on the whole does seem to be getting more complex and requires serious effort and training to master. In that respect, the continued addition of new features seems to have finally taken its toll in impacting overall usability. It is no longer possible to sit down and master Revit on one's own, without resorting to some kind of professional help. The documentation also has not kept up very well with the enhancements to the application and is not an adequate resource for learning the new features. The tutorials are all text-based and very long-winded. The lack of video tutorials really makes itself felt in this release.
Autodesk Revit 7 includes a host of enhancements and some new features, all of which are well thought out and very useful. Unlike the last release that introduced two new very critical features-design options and element borrowing in worksets-Revit 7 does not demonstrate any dramatic new feature additions. In that respect, it is more of an incremental release rather than a major upgrade. This explains why at Autodesk University, there was only a brief mention of Revit 7 and a lot more attention focused on the upcoming structural and MEP applications. As Revit stabilizes and matures as an application and expands as a platform, I hope its developers can reconnect with the focus on simplicity-achieved by many smarts under the hood-that has made the application stand way apart from its competitors in being almost effortless to learn and use.
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
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