Reality of object relationships

August 01, 2001 |

Imagine producing a realistic building model before a shovel ever hits the dirt at the construction site. Mechanical, structural and electrical components all wholly integrated, change orders kept to a minimum and all members of the building process sharing data through one computer program. That's the goal of the originators of Revit, an object-based computer-sided design (CAD) program.

Revit features a parametric change engine that acts on building components, annotation and views within the 3-D model to create association between all the construction information. In other words, each component within the building model possesses the properties of its real-world counterpart, including its parametric relationship to other building parts. For example, a window does not only have its attributes of height, width, glazing and frame type, but also is specified in terms of its placement within a wall and relationship to other windows. Since the entire building is the computer model, design intentions and changes are automatically reflected throughout the documentation set, whether they're drawings, details or schedules.

Starting with the massing function, the actual building model is created simultaneously with the massing model. Selecting the option to 'Show Mass' or 'Show Shell' toggles back and forth between the two ways of displaying the same building model, allowing one phase of design to continue while proceeding to the next level of building detail.

Tools hold the key

Revit exhibits its true parametric nature in the ceiling, floor, roof, door and window tools. Working in preliminary 'Sketch' mode, users can experiment with placement until 'Finish Sketch' is selected to locate the component in the model. All building parts such as walls, windows, doors and roofs have a 'Properties' listing to identify both their own object-based character and their relationships to other building components. For instance, if the walls are specified to extend to the underside of the roof, then any change to the roof slope alters the walls as well.

Data can be input into the program's R.S. Means CostWorks module, which consists of a database of built structures that allows a cost report to be quickly generated.

While having all data in one computer file makes for simple coordination, one downside is that all members of the building team must somehow share the same file and remain current with the input data. A new feature allows users to reserve one or more worksets, or groups of components, for editing from a central file. However, that data is temporarily unavailable for editing by the rest of the team until it is 'released.' Other users must then reload the latest worksets to keep current. This is a major improvement over the previous Revit releases, but it still requires diligent management.

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