Why Revit - BIM

2.6.1 Revit
We consider the Revit platform from the perspective of Revit Architecture.
Revit is the best-known and current market leader for BIM in architectural
design. It was introduced by Autodesk in 2002 after Autodesk acquired the
Revit program from a startup company. Revit is a completely separate platform
from AutoCAD, with a different code base and fi le structure. The version
reviewed here is 2011. Revit is a family of integrated products that currently
includes Revit Architecture, Revit Structure, and Revit MEP. It runs on Windows
OS and on Macs, using the Windows BootCamp® plug-in. It runs on both
32- and 64-bit processors and versions of the OS.
78 Chapter 2 BIM Design Tools and Parametric Modeling
As a tool: Revit provides an easy-to-use interface, with drag-over hints for
each operation and smart cursor. Its menus are well organized according to
workfl ow and its operator menus gray-out nonavailable actions within the current
system context. Its drawing generation support is very good; its drawing
production is strongly associative, so that drawing releases are easily managed.
It offers bidirectional editing from drawings to and from the model, and also
bidirectional editing from schedules for doors, door hardware, and the like.
Revit supports the development of new custom parametric objects and customization
of predefi ned objects. Its rule set for defi ning objects has improved with
each release and includes trigonometric functions. It can constrain distances
and angles and the number objects in an array. It also supports hierarchical
relations of parameters. Thus, an object can be defi ned by using a group of subobjects
with parametric relations. It is more diffi cult to set up global parameters
that can constrain assemblies of objects’ layout and sizes. The release of
the current API provides good support for external application development.
Revit has a very large set of product libraries, particularly its own Autodesk
SEEK library for specifi cation and design objects. It carries information for
about 850 different companies, and about 13,750 different product lines
(including over 750 light fi xtures). The products are defi ned in a mixture of
fi le types: RVA, DWG, DWF, DGN, GSM, SKP, IES, and TXT. They are accessible
from Masterformat, Uniformat, and Omniclass Table 23 (Products) formats.
There are about a half-dozen other sites with BIM products, where Revit
objects dominate.
As a platform: Revit, as the BIM market leader, has the largest set of associated
applications. Some are direct links through Revit’s Open API and others
are through IFC or other exchange formats. These are denoted (Dir) and
(IFC), respectively. DWF is another interface for Revit, denoted (Dwf).
Structural (with Revit Structure): Revit Structure (Dir), ROBOT (Dir),
and RISA structural analyses (IFC), BIM ME S.A.R.L. ETABS Link,
SismiCAD for FEA analysis, Graitec’s Advance and ARCHE, Fastrak
Building Designer, StruSoft FEM-Design, SOFTEK S-Frame, STAADPRO
via SIXchange, SOFiSTiK
Mechanical (with Revit MEP): Revit MEP (Dir), HydraCAD (fi re sprinklers),
MagiCAD (mechanical design), QuantaCAD (mechanical laser
scanning for as-builts), TOKMO (COBie facility operators handover—
see Chapter 3)
Energy and environmental: Ecotect, EnergyPlus, IES all indirect, Green
Building Studio via gbXML
Visualization: Mental Ray (Dir), 3D Max (Dir), Piranasi
Facility management: Autodesk FMDesktop® (Dwf), Archibus (IFC)
Revit interfaces with AutoCAD Civil 3D for site analysis, Autodesk
Inventor for manufacturing components, and with LANDCADD for site planning.
It interfaces with US Cost, Cost OS by Nomitech, Innovaya, and Sage
Timberline and also with Tocoman iLink for quantity takeoff for cost estimation.
Innovaya also provides 4D simulation links with Primavera and MS
Project schedules. Revit also supports links to Autodesk Navisworks through
DWF. VICO Offi ce supports both scheduling and quantity takeoffs. Revit has
links with specifi cations to e-SPECS® and BSD SpecLink through the BSD
Linkman mapping tool.
Revit is able to import models from SketchUp, AutoDesSys form•Z®,
McNeel Rhinoceros®, Google™ Earth conceptual design tools, and other systems
that export DXF fi les. Previously, these were visible but not referencable.
They are now referencable in Version 2011 (“referencable” here means that
users can select points on the objects, allowing dimensionally accurate referencing,
rather than visual dimensional coordination).
Revit Architecture supports the following fi le formats: DWG, DXF, DGN,
SAT, DWF/DWFx, ADSK (for building component), html (for area report),
FBX (for 3D view), gbXML, IFC, and ODBC (Open DataBase Connectivity).
Revit is a strong platform, especially because of its range of supporting
applications.
As an environment: Autodesk earlier invested in Web server capabilities,
such as Buzzsaw and Constructware. These existed from the 1990s using fi lelevel
support, with no visible strategy to support multiple platforms.
Revit carries object IDs and seems to manage them well. However, version
and change information is carried at the fi le level, not at the object level. This
limits synchronization of objects with different views in different fi les. Revit is
a platform but not a BIM environment. It needs to be able to manage objects,
similar to ArchiCAD’s DELTA Server capability, if it is to support large-scale
BIM environments (for more detail see Chapter 3, Section 3.5).
Revit’s strengths: As a design tool, Revit 2011 is strong; it is intuitive; its
drawing production tools are excellent. However, many designers wishing to
go beyond the built-in objects’ limitations use other tools to design in a more
freeform manner, and then import the results into Revit for production modeling.
Revit is easy to learn and its capabilities are organized in a well-designed
and user-friendly interface. It has a very broad set of object libraries, developed
both by themselves and by third parties. Because of its dominant market
position, it is the preferred platform for direct link interfaces with other BIM
tools. Its bidirectional drawing support allows for information updates and
management from drawing and model views, including schedules. It supports
concurrent operation on the same project. Revit includes an excellent object
library (SEEK) that supports a multiuser interface.
Revit’s weaknesses: Revit is an in-memory system that slows down signifi -
cantly for projects larger than about 300 megabytes. It has a few limitations on
parametric rules. It also has only limited support for complex curved surfaces.
Lacking object-level timestamps, Revit does not yet provide needed support for
full object management in a BIM environment.

BIM Handbook
A Guide to Building Information
Modeling for Owners, Managers,
Designers, Engineers, and Contractors
Second Edition
Chuck Eastman
Paul Teicholz
Rafael Sacks
Kathleen Liston