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AEC

1-2-3 Revit: BIM Concept to Completion

14 May, 2005 By: AIA ,Rick Rundell Cadalyst

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Autodesk Revit Building combines the expressive and built forms of a building design

You spend the bulk of your time on a design project on the detailed design and construction document phases of a project, but the building's general appearance and cost are largely fixed very early on, during conceptual design. Because the conceptual design is so crucial to the final building design, it makes sense to have a consistent flow of digital building information from beginning to end. However, the conceptual modeling tools and the detailed design tools are usually separate environments (in unrelated software), so the building models resulting from these two design stages have no association -- digitally speaking.

This article describes how Autodesk's BIM solution, Autodesk Revit Building, links those two environments and the benefits of that relationship.

Conceptual Design in Isolation
Conceptual building models often are developed using specialized software that allows architects to extrude forms, push and pull the geometry, create carved shapes or forms and so forth. When the schematic design is complete, the model is usually exported to a standard CAD file format (DXF, DWG, etc.) and imported into a detailed design solution.

The drawbacks of disconnected schematic and detail design models are clear. First, there's the circuitous transition from one to the other. Importing and exporting files can be time consuming and error prone. Important building information captured during the schematic design is lost, most notably design intent. And what happens if the design already progressed to the detailed design tool, but there's an unexpected change to the schematic design (due perhaps to a last-minute client revision)? Do you revise the conceptual model, import it into the detailed design model and try to manually synchronize the models? Or do you just delete the affected detailed design elements and start over, based on the revised conceptual design? What about work you've already done on drawings or renderings? Do you try to coordinate those changes to the new design? In any case, you'll waste time and money.

Conceptual Modeling with Autodesk Revit Building Maker
Autodesk Revit connects the conceptual and detailed design stages with Revit Building Maker, a conceptual design toolset within the Revit building information modeling solution. With Revit Building Maker, the designer develops conceptual models independently and maps them directly to building model components as the design progresses -- all from the standard Revit environment.

You can create building forms from scratch using basic 3D shapes, or you can generate them by sweeping 2D profiles. Alternatively, you can use existing conceptual design studies from your favorite 3D modeling software by importing ACIS solid models into Revit Building Maker. You can join forms together or subtract them to create complex building geometry. You can associate material properties with masses, which are then used during rendering. Architects can quickly iterate through design studies and create compelling renderings of their conceptual design. Even at this early stage, the designer can validate design features by slicing the model up into floors and calculating gross floor areas and overall building volumes (figure 1).

Schematic Design to Design Development
At any point, the designer can convert individual faces of these building masses to building model components such as: walls, roofs, floors, curtain systems, etc. Although these model components aren't locked to the faces, Revit maintains the relationships between the conceptual model geometry and the building components that are formed by them -- so changes to the conceptual model can ripple through to the detailed design model and even construction documents.

For example, if the height of a cylindrical building atrium needs to be increased, the designer can modify the cylindrical mass representing the atrium, and then select the walls that need to be updated. Revit will adjust the affected design components accordingly.

The standard separation between the two design phases is gone. The designer works fluidly between the conceptual model and the building model while both design intent and detail is captured at the moment of conceptualization.

In addition, powerful building design tools usually associated with detailed design are available in the conceptual design phase as well: drawing production (elevations, sections, etc.), informational takeoff/schedules, hidden line and shaded 3D views (even with shadows, for very effective presentation graphics), and integration with high-end rendering solutions such as Autodesk VIZ or 3ds max.

Unified Design Environment
Revit Building Maker is not only a powerful tool for common conceptual and schematic tasks, it also strengthens the relationship between the exploratory nature of conceptual design and design development. Revit Building Maker helps designers gain a cumulative understanding of the relationship between expressive and built form as a design develops.