User Interface: BIM design tools are quite complex and have much greater functionality than earlier CAD tools. Some BIM design tools have a relatively intuitive and easy-to-learn user interface, with a modular structure to their functionality, while others place more emphasis on functionality that is not always well-integrated into the overall system. Criteria to be considered here include: consistency of menus across the system’s functionalities following standard conventions; menu-hiding that eliminates irrelevant actions not meaningful to the current context of activities; modular organization of dif- ferent kinds of functionality and online help providing real-time prompts and command-line explanation of operations and inputs. While user interface issues may seem minor, a poor user interface results in longer learning times, more errors, and often not taking full advantage of the functionality built into the application. User interface issues across a set of integrated tools are also important at the platform level; we review those issues in the next section.
Drawing Generation: How easy is it to generate drawings and drawing sets and to maintain them through multiple updates and releases? Assess- ment should include quick visualization of the effects of model changes on drawings, strong associations so that model changes propagate directly to drawings and vice versa, and effective template generation that allows drawing types to carry out as much automatic formatting as possible. A more thorough review of functionality is provided in Section 2.3.3.
Ease of Developing Custom Parametric Objects: This is a complex capa- bility which can be defined at three different levels:
(1) Existence and ease-of-use of a sketching tool for defining parametric objects; determining the extent of the system’s constraint or rule set (a general constraint rule set should include distance, angle including orthogonally, abutting faces and line tangency rules, “if-then” conditions and general algebraic functions)
(2) ability to interface a new custom parametric object into an existing parametric class or family, so that an existing object class’s behavior and classification can be applied to the new custom object.
(3) ability to support global parametric object control, using 3D grids or other control parameters that can be used to manage object place- ment, sizing, and surface properties, as required for the design. These issues are explained further in Section 2.2.1.
Complex Curved Surface Modeling: Support for creating and editing complex surface models based on quadrics, splines, and nonuniform B-splines is important for those firms that currently do this type of work or planning to in the future. These geometric modeling capabilities in a BIM tool are foundational; they cannot be added on later.
Other Tool-Level Capabilities: Support for tool capabilities beyond the basics include clash detection, quantity takeoffs, issue tracking, and incorporation of product and construction specifications. These are appropriate for different uses and workflows and are considered in more detail in Chapters 5, 6, and 7. We also consider the support provided by a large user community on the Web.