The Basics of BIM: What Is Revit?


The Basics of BIM

In this chapter, we cover principles of a successful building information modeling (BIM)
approach within your office environment and summarize some of the many tactics possible
using BIM in today’s design workflow. We explain the fundamental characteristics of
maximizing your investment in BIM and moving beyond documentation with an informationrich
model.
In this chapter, you’ll learn to:
◆ Understand a BIM workflow
◆ Leverage BIM processes
◆ Focus your investment in BIM

What Is Revit?

Autodesk Revit software is a BIM application that uses a parametric 3D model to generate
plans, sections, elevations, perspectives, details, and schedules—all of the necessary
instruments to document the design of a building. Drawings created using Revit are not a
collection of 2D lines and shapes that are interpreted to represent a building; they are live views
extracted from what is essentially a virtual building model. This model consists of a compilation
of intelligent components that contain not only physical attributes but also functional behavior
familiar in architectural design, engineering, and construction.
Elements in Revit are managed and manipulated through a hierarchy of parameters
that we will discuss in greater detail throughout this book. These elements share a level of
bidirectional associativity—if the elements are changed in one place within the model, those
changes are visible in all the other views. If you move a door in a plan, that door is moved in
all of the elevations, sections, perspectives, and so on in which it is visible. In addition, all of
the properties and information about each element are stored within the elements themselves,
which means that most annotation is merely applied to any view and is transient in nature.
When contrasted with traditional CAD tools that store element information only in the
annotation, Revit gives you the opportunity to more easily extract, report, and organize your
project data for collaboration with others.
Before we get started with a detailed examination of Revit, let’s take a step back and develop
a better understanding of the larger concepts of building information modeling and how they
will affect your practice of architecture.

Understanding a BIM Workflow

According to the National Institute of Building Sciences (www.nibs.org), a BIM is defined as “a
digital representation of physical and functional characteristics of a facility” that serves as a “shared
knowledge resource for information about a facility forming a reliable basis for decisions during its
life cycle from inception onward.” Although this is the definition of the noun used to represent the
electronic data, the verb form of building information modeling is equally important. BIM is both a
tool and a process, and one cannot realistically exist without the other. This book will help you to
learn one BIM tool—Revit Architecture—but it will also teach you about the BIM process.
Building information modeling implies an increased attention to more informed design
and enhanced collaboration. Simply installing an application like Revit and using it to replicate
your current processes will yield limited success. In fact, it may even be more cumbersome than
using traditional CAD tools.
Regardless of the design and production workflow you have established in the past, moving
to BIM is going to be a change. To begin, we’ll cover some of the core differences between a
CAD-based system and a BIM-based one.
Moving to BIM is a shift in how designers and contractors approach the design and
documentation process throughout the entire life cycle of the project, from concept to
occupancy. In a traditional CAD-based workflow, represented in (Figure 1.1), each view is
drawn separately with no inherent relationship between drawings. In this type of production
environment, the team creates plans, sections, elevations, schedules, and perspectives and must
coordinate any changes between files manually.

(Figure 1.1)

Introduction- The Basics of BIM 1

In a BIM-based workflow, the team creates a 3D parametric model and uses this model to
generate the drawings necessary for documentation. Plans, sections, elevations, schedules,
and perspectives are all by-products of creating a building information model, as shown in

 (Figure 1.2). This enhanced representation methodology not only allows for highly coordinated
documentation but also provides the basic model geometry necessary for analysis, such as
daylighting studies, energy usage simulation, material takeoffs, and so on.

(Figure 1.2)

Introduction- The Basics of BIM 2

Leveraging BIM Processes

As architects or designers, we have accepted the challenge of changing our methodology to adapt
to the nuances of documentation through modeling rather than drafting. We are now confronted
with identifying the next step. Some firms look to create even better documents, whereas others
are leveraging BIM in building analysis and simulation. As we continue to be successful in
visualization and documentation, industry leaders are looking to push BIM to the next level. Many
of these possibilities represent new workflows and potential changes in our culture or habits, which
require you to ask a critical question: What kind of firm do you want, and how do you plan to use BIM?
As the technology behind BIM continues to grow, so does the potential. A host of things are
now possible using a building information model; in fact, that list continues to expand year after
year. (Figure 1.3) shows some of the potential opportunities.

Figure 1.3

Introduction- The Basics of BIM 3

We encourage you to explore ongoing research being conducted at Penn State University
(http://bim.psu.edu), where students and faculty have developed a catalog of BIM uses and
project implementation guidelines that have been adopted into the National BIM Standard-
United States, version 2 (http://nationalbimstandard.org). Another important aspect of
supporting numerous BIM uses is the development of open standards. The organization known
as buildingSMART International (www.buildingsmart.org) provides a global platform for
the development of such standards. Groups from a number of regional chapters around the
world are generating information exchange standards that will soon have a profound impact
on the ways in which we share model data with our clients and partners. Some of the latest
developments are:
◆ IFC (Industry Foundation Classes) version 4
◆ COBie—Construction–Operations Building Information Exchange
◆ SPie—Specifiers’ Properties Information Exchange
◆ BCF—BIM Collaboration Format
◆ UK-based BIM Task Group (www.bimtaskgroup.org)
For a general overview of the approach to standardizing exchanges with information
delivery manuals (IDMs) and model view definitions (MVDs), visit www.buildingsmarttech.
org/specifications.
When moving to the next step with BIM—be that better documentation, sustainable analysis,
or facility management—you should look at your priorities through three different lenses:
◆ Visualize
◆ Analyze
◆ Strategize
Understanding these areas, specifically how they overlap within your firm, will help you
define your implementation strategy for BIM tools and processes.

Visualizing

Creating documentation using BIM gives you the added advantage of being able to visualize the
project in 3D. Although this was initially conceived as one of the “low-hanging fruits” of a BIM
workflow, this benefit has led to an explosion of 3D graphics—perspectives, wire frames, cloud
renderings, and animations—within the industry as a means to communicate design between
stakeholders on a project.
This digital creation of the project has given us a variety of tools to communicate aspects
of the project. It becomes “architecture in miniature,” and we can take the model and create a
seemingly unlimited number of interior and exterior visualizations. The same model may be
imported into a gaming engine for an interactive virtual experience. Clients no longer need to
rely on the designer’s pre-established paths in a fly-through—they can virtually “walk” through
the building at their own pace, exploring an endless variety of directions. The same model can
then be turned into a physical manifestation either in part or in whole by the use of 3D printers
(known as rapid prototyping), creating small models (Figure 1.4) in a fraction of the time it
would take to build one by hand. Many types of visualization are currently possible with BIM.

(Figure 1.4)

Introduction- The Basics of BIM 4

If we consider a complete spectrum of representations, from tabular data to 2D documentation
and then to 3D visualization, tremendous opportunities exist to transform the notion of traditional
design deliverables. Schedules give you instantaneous reports on component quantities and space
usage, whereas plans, sections, and elevations afford you the flexibility to customize their display
using the information embedded in the modeled elements. For example, the plan in Figure 1.5
shows how color fills can be automatically applied to illustrate space usage by department.

Figure 1.5

Introduction- The Basics of BIM 5

Expanding 2D documentation to include 3D imagery also gives you the ability to clearly
communicate the intent of more complex designs. It may even have a positive effect on
construction by transcending possible language barriers with illustrative documentation
rather than cryptic details and notations. Figure 1.6 shows a basic example of a drawing sheet
composed of both 2D and 3D views generated directly from the project model.

Figure 1.6

Introduction- The Basics of BIM 6

The obvious benefit to creating a complete digital model of your building project is the
ability to generate a wide variety of 3D images for presentation. These images are used to
not only describe design intent but also to illustrate ideas about proportion, form, space, and
functional relationships. The ease at which these kinds of views can be mass-produced makes
the rendered perspective more of a commodity. In some instances, as shown in the left image of
Figure 1.7, materiality may be removed to focus on the building form and element adjacencies.
The same model is used again for a final photorealistic rendering, as shown in the right image
of Figure 1.7.
By adding materiality to the BIM elements, you can begin to explore the space in color and
light, creating photorealistic renderings of portions of the building design. These highly literal
images convey information about both intent and content of the design. Iterations at this level
are limited only by processing power. The photorealism allows for an almost lifelike exploration
of color and light qualities within a built space even to the extent of allowing analytic brightness
calculations to reveal the exact levels of light within a space.

Figure 1.7

Introduction- The Basics of BIM 7a Introduction- The Basics of BIM 7b

The next logical step is taking these elements and adding the element of time. In
Figure 1.8, you can see a still image taken from a phasing animation (commonly referred to
as a 4D simulation) of a project. Not only do these simulations convey time and movement
through space, but they also have the ability to demonstrate how the building will react or
perform under real lighting and atmospheric conditions. All of this fosters a more complete
understanding of the constructability and performance of a project before it is realized.

Figure 1.8

Introduction- The Basics of BIM 8

"BIM as a Single Source Model
In the early 2000s, if you wanted to create a rendering, a physical model, a daylighting model,
an energy model, and an animation, you would have had to create five separate models and use
five different pieces of software. There was no ability to reuse model geometry and data between
model uses. One of the key uses of BIM is the opportunity to repurpose the model for a variety of
visualizations. This not only allows you to not have to re-create geometry between uses, but also
ensures you’re using the most current information in each visualization because it all comes from
the same source. As the capacity of cloud rendering and analysis grows, the feedback will no longer
need to process locally and you’ll be able to receive feedback faster."