In parametric modeling, a designer uses a computer program to create virtual objects that have real-world qualities. Components within the computer program interact in a realistic manner. Because all data can be stored in a single file containing a single “three-dimensional” model, there is no disconnect among different elements of a project. For example, when information is changed in one view, it is automatically updated in all other views. Construction drawings and project data are intrinsically tied to the “three-dimensional” model and therefore updated automatically whenever the model is altered.
Revit, a building information modeling (BIM) program, is quite different from other computer programs such as AutoCAD, Rhinoceros, and SketchUp. In AutoCAD, a project is represented by abstract, two-dimensional lines, shapes, and colors. Various drawings describing a single project must be generated separately from each other; their properties are not governed by a single, consolidated, “three-dimensional” model. Thus, a section or elevation drawing is not updated automatically when information is altered in a floor plan drawing. In Rhinoceros and SketchUp, information appears “three-dimensionally” in a single digital model, but is nonetheless represented by abstract geometry instead of separate, information-rich components. A “wall” or a “roof” is not recognized as such.