Chapter 1 Discussion Questions
2.5 OVERVIEW OF THE MAJOR BIM DESIGN PLATFORMS
In this section, we summarize the major functional and performance capabili- ties that distinguish different BIM platforms, considered as having both tool and platform functionality, as presented in earlier sections of this chapter. We also consider them in relation to their supporting a BIM environment. The capabili- ties apply to both design-oriented systems as well as fabrication BIM design
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tools. These distinguishing capabilities are proposed for those wishing to under- take a fi rst-level review and assessment of alternative systems, so as to make a well-informed decision within the project, offi ce, or enterprise. The choice affects production practices, interoperability, and to some degree, the functional capabilities of a design organization to do particular types of projects.
We organize the important features at three levels of applicability: as a tool, as a platform, and as an environment, as defi ned in Section 2.4.We emphasize that no one application will be ideal for all types of projects. Ideally, an organi- zation would have several platforms that it supports and moves between for specifi c projects. Some uniquely support communication between different applications; others may support collaboration with a particular fabricator or consultant. Fabricators are less likely to need multiple platforms.
Adopting a BIM design application, as a tool and/or platform, is a signifi cant undertaking. Adoption is also discussed in later chapters, especially regarding their intended use, for design and engineering in Chapter 5, for contractors and construction management in Chapter 6, and for fabricators in Chapter 7.
They are also considered for their support of being managed within a BIM environment, as developed in Chapter 3. Decisions about applications involve understanding new technologies, the new organizational skills needed, and then learning and managing those skills. These challenges will recede over time, as the learning curve and practices surrounding BIM use become more ingrained in practice. Because the functionality of BIM design applications is changing quickly, it is important to look at reviews of the current versions in AECBytes, Catalyst, or other AEC CAD journals and collaboration sites such as LinkedIn.
Within the common framework of providing object-based parametric modeling, BIM design applications embody many different kinds of capabili- ties, some at the tool and some at the platform levels. We discriminate the issues associated with their use as a tool and as a platform, with comments about their support at the BIM system environment level.
2.5.1 As a BIM Design Tool
Below, we describe the discriminating design tool capabilities in rough-rank based on our sense of their level of importance. We take parametric model generation and editing as fundamental. We assume that model defi nition and drawing production are the current primary tool-level uses for building mod- eling systems. Model generation and editing is considered multifaceted, in terms of user interface, custom objects, and complex surface modeling.
User Interface: BIM design tools are quite complex and have much greater functionality than earlier CAD tools. Some BIM design tools have a relatively
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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 is- sues 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 defi ned at three different levels:
(1) Existence and ease-of-use of a sketching tool for defi ning paramet- ric 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 classifi cation 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 fi rms 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.
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Other Tool-Level Capabilities: Support for tool capabilities beyond the basics include clash detection, quantity takeoffs, issue tracking, and incor- poration of product and construction specifi cations. These are appropri- ate for different uses and workfl ows 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.
2.5.2 As a BIM Platform
Below we describe the major discriminating capabilities of an application meant to serve as a design platform. The basic functionality of BIM design applications was initiated as a tool and began serving the idea of a platform as the uses of building model information were recognized. The requirements of a BIM platform have grown in importance as the potential uses of building infor- mation have increased. Most BIM platforms operate on the Microsoft Windows platform with a wide range of interfacing tools; a few support the Apple Mac- intosh, where the range of applications to interface with is fewer. We enumer- ate them in rough-rank order, based on our sense of their level of importance.
Scalability: This is the ability to handle combinations of a large project scale and modeling at a high level of detail. This involves the ability of the system to remain responsive regardless of the number of 3D parametric objects in the project. This capability can be important at the tool level, but the scope of a tool at any one time is usually limited. The scalabil- ity of a design becomes critical when hierarchical parameters are used to manage large sections of façade or the whole building envelope. A funda- mental issue is the degree that the system is disk-based, in terms of data management, rather than memory-based. Disk-based systems are slower for small projects because of disk read/write speeds, but their delay time grows slowly as the project size grows. Memory-based systems are usually quicker under light loads, but performance drops quickly once memory space is exhausted. Scalability is partially limited by the operating sys- tem; Windows XP, 32-bit version, without special settings, only supports up to 2 gigabytes of working memory for a single process. Sixty-four-bit architectures for Windows and Snow Leopard eliminate the memory use restriction and are becoming inexpensive and common. Graphic card per- formance also is important for some systems. This topic is discussed in more detail in Section 2.3.4.
Tool Interfaces: As a platform, a BIM application needs to be able to present a large range of information, as geometry, properties, and as rela- tions between them, to other applications. Typical uses include structural,
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energy, lighting, costs, and other analyses during design; clash detection and issues tracking for design coordination; purchasing and materials tracking; and task and equipment scheduling for construction. Tool interfaces of importance depend on the intended use of the BIM platform, defi ned by particular patterns of workfl ow. We assess their appropriate- ness in the tools and workfl ows in the chapters that address their use in different contexts—Chapters 5, 6, and 7.
Libraries of BIM Elements: Each BIM platform has various libraries of predefi ned objects that can be imported for use. These can be helpful by eliminating the need to defi ne them yourself. In general, the more prede- fi ned objects, the more helpful. There is a further level of discrimination regarding how good the objects are for different uses. Currently, there is little effort to standardize the structure of object information beyond geometry. Here we are referring to specifi cations for selection, specifi ca- tions for use in analyses, service manuals, material properties for use in rendering, and other similar uses. Only the smartBIM Library, reviewed in Chapter 5, has begun to address these issues, to our knowledge. In considering different platforms, the availability of predefi ned building objects facilitates work on that platform.
Platform User Interface Consistency: Platform interfaces have different criteria according to two different scenarios of use. In one case, the tools are operated by specialists in different departments in a large fi rm, or by consultants. In this case, each tool has its own logic and is addressed in the tool-level criteria. In the other scenario, the tools are shared and used by multiple platform users. In this case, the consistency across tools is very important, for ease of learning and use. It is a challenge because of the wide range of functionality to be supported.
Extensibility: Extensibility capabilities are assessed based on whether a BIM platform provides scripting support—an interactive language that adds functionality or automates low-level tasks, similar to AutoLISP® in AutoCAD—an Excel format bidirectional interface, and a broad and well- documented application programming interface (API). Scripting languages and Excel interfaces are generally for end users, while an API is intended for software developers. These capabilities are needed depending on the extent to which a fi rm expects to customize capabilities, such as custom par- ametric objects, specialized functions, or interfaces to other applications.
Interoperability: Model data is generated, in part, to share with other applications for early project feasibility studies, for collaboration with en- gineers and other consultants and later for construction. Collaboration is
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supported by the degree that the BIM platform provides interfaces with other specifi c products and, more generally, its import and export sup- port of open data exchange standards. Both these types of interfaces are reviewed in detail in Chapter 3. The open exchange standards are getting more elaborate, starting to support workfl ow-level exchanges. This requires export and import translations to be varied. An easily customizable import and export facility is highly benefi cial. Both tool interfaces and the more general aspects of interoperability are considered here.
Multiuser Environment: Some systems support collaboration among a design team. They allow multiple users to create and edit parts of the same project directly from a single project fi le and manage user access to these various information parts. This can work in a disk-based plat- form. It makes less sense in a memory-based BIM platform, where the multiple users are competing for the same address space and hardware resources.
Effective Support for Managing Properties: Properties are an integral part of the data needed for most BIM support tools. Property sets need to be easily set up and associated with the object instances they describe. Tools for this capability vary a lot on different platforms.
2.5.3 As a BIM Environment
At the beginning of the BIM age, it was thought that a single application could serve the needs at all three levels: as a tool, as a platform, and as an environ- ment. That idealism has slowly waned, as the scale of a BIM project and the systems to support it have become understood. An important capability needed to globally support advanced BIM projects is to support work in a multiplat- form and multipresentation environment. A BIM environment needs the ability to generate and store object instances for different tools and platforms and to manage that data effectively, including change management at the object level.
This issue is addressed more centrally in Chapter 3, Section 3.5. This can be handled by a change fl ag or a timestamp that gets updated whenever an object is modifi ed. The goal is to exchange and manage objects and sets of objects rather than fi les.
Below we offer an overview of the current capabilities of the major building model generation platforms. Some reviewed support only architectural design functions, others only various types of fabrication-level building systems, and others both. Each assessment is for the version of the software system noted;
later versions may have better or worse capabilities. We review them according to the criteria developed above.
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