2 Lecture 02

Building Information Modeling

Modeling Building Products and BIM Tools

Jinyue Zhang @ University of Toronto 27/07/2013 Modeling Building Products and BIM Tools 1

Agenda• The evolution to parametric object-based modeling in

the AEC/FM industry– Decision on modeling approach– Solid modeling in general– Early effort of building models– Object-based parametric modeling– Degrees of parametric modeling

• Computer visualization

• Parametric modeling of buildings

• BIM environments, platforms, and tools

• Major BIM systems

• Lightweight modeling applications

27/07/2013 Modeling Building Products and BIM Tools 2

Evolution to parametric object-based modeling• Decision on modeling approach

– Purpose of the model– Model complexity– Building size– Hardware/Software

• Solid modeling in general– B-rep– Constructive Solid Geometry (CSG)

• Early effort of building models

• Object-based parametric modeling

• Degrees of parametric modeling


Purpose of the Model

Visualization

Design Coordination Construction Coordination

Conceptual Design


Conceptual Modeling• Main purpose of the model is

to help making design decisions.

• The model does not necessarily include the entire building (e.g. internal structures can be missing).

• Accuracy is not relevant.

• Level of detail is typically lower than that in design models developed later.

• Materials can be symbolic or missing. http://www.sketchup.com


Modeling for Visualization• Not necessary to model the

entire building

• Only the elements of the actual view need to be shown

• Level of modeling detail should depend on the image quality and the distance from the camera

• Correct texture coordination and lighting is essential


Modeling for design coordination• The entire building has to be

modeled.

• Necessary information has to be assigned to it.– Often include information of

architecture and construction– May include information of cost,

energy, structure

• Model should be made of real architectural elements (walls, slabs, roofs, etc.) for correct calculation results.

• Modeling detail level should be appropriate for the required drawing representations.


Modeling for construction coordination• Time and cost information is

attached to the BIM model by linking schedules and estimating data (5D).

• The main purpose of the 3D model is to calculate the exact quantities of materials and to identify any conflicts, collisions in the construction. Thus model accuracy is critical.

• Elements of composite building structures can be described in estimating data instead of modeling them in 3D.

Time

(Linked schedules)

Cost

(Linked estimating

data)

BIM


Model complexityM

odel

Com

plex

ity

OrganicTraditional

Zaha HadidLe Corbusier Frank O. Gehry


How can you model these buildings?• Simplify

– The level of detail shouldn’t exceed the actual requirements.

• Divide– Share the virtual building between the project team members.

• Use the appropriate software– There is no out of the box solution. You have to combine

several applications for the best results.

Frank O. Gehry Santiago CalatravaBird’s Nest (Beijing)


Model size: what makes a model big/slow?• Size of the project file

– # of building elements– # of 3D polygons

• Lack of team working

• Inappropriate computer hardware


Model size: what can we do?• Reduce the number of polygons

– Simplify the memory excessive model elements

• Turn off the invisible elements– Use layer combinations and selections

• Divide the project– Modules, Xrefs and team working solutions help to

share the work with other project team members

• Use appropriate hardware– See next slide


Hardware requirements

• CPU– Graphical calculations, 2D and 3D operations

• Memory– 3D operations

• HD– Safe storing of project, backup and cache files

• Graphic Card– Navigation in 3D, OpenGL support

All in all, the computer configuration has tomatch with the hardware requirements of the CAD software


Software solutions

Visualization

Documentation

BIMmodel

Classic BIMmodeling approach

One application does all:

• Modeling

• Documentation

• Visualization

BIM Application


Software solutions

VisualizationDocumentation

BIMapplicationConceptual

modeler

Freeform modeler

Rendering application

ConceptualVisualization

Complex modelingand visualizationsolution

•Specialized applications combined with BIM software.

•Parts of the 3D model are created in external modeling applications.










Solid modeling

• R&D on computer tools for interactive 3D design in last four decades

• Starting the 1960s, earliest 3D geometry representation– Movie industry, architectural/engineering, gaming

• Solid modeling in 1973: a major step towards a way to edit and modify complex shapes– Ian Braid at Cambridge University– Bruce Baumgart at Stanford University– Herb Voelcker at University of Rochester


Two forms of solid modeling

• Boundary representation approach, or B-rep

• Constructive Solid Geometry, or CSG


B-rep

• Shapes are represented as a closed, oriented set of bounded surfaces.

• Volume-enclosing criteria, regarding orientation, connectedness, and surface continuity among others


Well-formed B-rep shape

• Simply computed shapes

• Swept shapes


Overlapped shapes

• Editing operations (Boolean operations):– union, intersection, and difference (subtraction)

Addition Subtraction Intersection

A complex shape generated by Boolean operations


Constructive Solid Geometry (CSG)

• Shapes as a set of functions that define the primitive polyhedra, similar to B-rep

• Also use Boolean operations

• Where is the difference?


Constructive Solid Geometry (CSG)


B-rep and CSG: which one is better?

• Initially two competitive methods

• B-rep– Excellent for direct interaction, for computing mass

properties, rendering and animation, and for checking spatial conflicts

• CSG– Great for editing and modifying combined shapes

• A combined approach – CSG for editing– B-rep for visualizing, measuring, clash detection










Early efforts at building models

• Scottish Special Housing Authority (SSHA) Housing System (1969-1973)– Developed by the Architectural Research Unit at the

University of Edinburgh– Two major projects

• Housing unit design• Site planning for housing estates

• OXSYS and Building Design System (1970-1978)– Developed by Oxford Regional Health Authority to

facilitate hospital construction


SSHA Housing System• Floorplan design system

– Blobs to represent floorplan elements– A dedicated data structure to describe the blob


SSHA Housing System

• Site planning system– For site layout and cost

estimation– Define the contour and

ground plane conditions– Assign housing and

garage units, roads, drainage lines, landscape areas, footpaths, and retaining walls to the site for quick cost estimation


OXSYS and Building Design System (BDS)

• OXSYS: a prefabricated building system developed by the Oxford Regional Health Authority– A post-and-beam and slab system of construction– Based on a predefined set of building components– Attributes attached to building components– A separated application for document generation

• Commercialized in 1978 as BDS– A strong example of object-based modeling– Integration of multiple applications– Withdrawn from the market when full 3D and solid

modeling geometry is available in production systems.27/07/2013 Modeling Building Products and BIM Tools 29

OXSYS and Building Design System (BDS)










Object-based parametric modeling

• First developed and refined for mechanical system design

• Technical foundation of all current generation of BIM architectural design tools

• An element class instead of individual instances– Fixed/parametric geometry parameters– Relations– Rules

• Relations and rules to make the object edit itself


An example of a wall object family• X1 and X2 offsets to define the

thickness of the wall• Profiles to define some special

types, for example tapered wall • Relations to other walls, floor,

and ceiling controlled by rules• Special conditions to consider

– No overlapping openings– Straight or curved wall control

line– Connection types with floor,

ceiling, other walls, stairs, ramps, columns, beams, and other building elements

– Walls with different types of construction and finishes


An example of a window object family


A specific domain

• Modeling building products is different to modeling efforts in many other industries– A very large number of relatively simple parts– Predictable behaviours (relations and rules) – Huge amount of information at construction-level

detail– Drawing production with architectural convention is

mandatory










Different levels of parametric modeling

• The simplest level– Parametric solid modeling: elements defined by a few

parameters for geometric and spatial relations– Example: AutoCAD in architectural design

• A better level– Parametric assemblies: objects automatically update

when parameters are changed– Example: recent status of Architectural Desktop

• An ideal level– Full parametric modeling: parameters defining one

shape to be linked through rules to the parameters of another shape


Agenda

• The evolution to parametric object-based modeling in the AEC/FM industry







Computer visualization

• History

• Computer visualization methods

• Visualization workflow

• Technological background


Technology Timeline

1960 1970 1980 20001990

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http://accad.osu.edu/~waynec/history/timeline.html

• Started in 1960s• Advancement in many disciplines

– Display technologies– Data input methods– Visualization algorithms– Picture compression technologies

• Time between the invention and implementation


Visualization Techniques• Photorealistic images (rendering)

NHS office complex by paastudio


Visualization Techniques• Artistic images


Visualization Techniques• Sun studies


Visualization Techniques• Fly through animations


Standard BIM Visualization Workflow

Images

Animations

VR

BIM Model

RenderingEngine

VREngine

AnimationTool

BIM APPLICATION


Complex Visualization Workflow

Images

Animations

VR

ExternalRenderingApplication

ExternalVR

Application

ExternalAnimationApplication

BIM Model

BIM APPLICATION

ExternalMovie-editingApplication

ExternalImage-editing

Application


Photorendering• Objective: Creating

photorealistic images based on the BIM model using an internal or external rendering engine

• Process:– Modeling– Scene layout setup – Rendering NHS office complex by paastudio


Scene Layout Setup• Adjusting the materials

– Texture positioning– Color adjustment– Shininess– Bump maping, transparency

• Light Settings– General light– Sun light– Brightener lights

• Placing Cameras– Positioning– Camera angles


Non-photorealistic renderings• Objective: Creating artistic style

images based on the BIM model using special rendering engine and/or photo editing software

• Process A:– Modeling– Scene layout setup – Non-Photorealistic Rendering

• Process B:– Modeling– Scene layout setup – Photorealistic Rendering– Modifying the image in a photo-

editing softwareNHS office complex by paastudio


Sun studies• The sun study is a special type of computer animation.

The objective of making sun studies is to visualize the natural lighting conditions on a given location of the building at a particular day of the year. Unlike in fly through animations the camera position remain stable

• Workflow– Modeling– Scene layout setup– Day settings– Sun study calculation


Fly Through Animations• Objective: Creating movies of the building along a

predefined camera path, based on the BIM model, using internal or external animation tools

• Workflow– Modeling– Scene layout setup– Defining camera path– Movie calculation


Agenda








Parametric modeling for AEC• Example of Boeing 777

– Rules to define airplane interiors for looks, fabrication, and assembly

– Computational Fluid Dynamics: parametric adjustments of outside shape for many hundreds of airflow simulations

– Virtual assembly in computer to eliminate 6000+ possible changes

• Parametric design• Parametric modeling for construction• User-defined parametric objects


Parametric building design• Predefined families of building elements

• Third party object families

• Predefined object behaviours and rules

• Fixed building object models

• Spaces defined in BIM tools


Predefined object classes


Predefined object classes


Third party object families• Available for downloading and use from a number of

Web sites

• Some are open and free, others are proprietary

• Modern equivalent of drafting block libraries in 2D era, but more useful and powerful

• Examples: furniture, plumbing and electrical equipment, proprietary fasteners for concrete fabrication, etc.

• Some are in generic type, others are models of specific products

• More to discuss


Predefined behaviours and rules• Behaviours to identify how they can be linked into

assemblies and automatically adjust their own design– The height of a wall will change to keep connected to the

ceiling when the ceiling is moved to a higher place.– The space information will update automatically if the boundary

walls change.

• What attributes to attached with an object?

• Can user define their own features/attributes about an object?


Fixed building object models• Not all object models in BIM are parametric• Examples: furniture with fixed dimensions, specific

lighting fixtures, etc.• Available in most thirty party libraries


Spaces in BIM is important• Environmentally conditioned building spaces• Shape, volume, surfaces, environmental quality,

lighting, and other properties


Parametric modeling for Construction• Inside of architectural elements

• Modeling at fabrication level

• Example of concreting engineering

• Fabrication-level CAD systems


More detailed modeling• Can we model things inside of architectural elements?

• Parametric layout of nested assemblies of objects– Example: stud framing within a layer of generic wall

• Objects are parts which are composed into a system

• Rules to determine how the components are organized


Modeling at fabrication level• Early system started from simply 3D layout for

designing connections.

• Steel fabrication examples: Design Data’s SDS/2, Tekla Structures, and AceCad’s StruCad.

• Later the capabilities were enhanced to support automatic connection design based on loads and member sizing, and to associated with CNC cutting and drilling machines.

• Started in steel fabrication, but now expending to precast concrete, reinforced concrete, metal ductwork, piping, and other building systems.


Precast concrete panel: an example• Shape operations to create reveals, notches, bullnoses, and cutouts

• Parametrically design for precast reinforcing embedded

• Automatically generate piece mark drawings


Fabrication-level CAD systems• Some are not general-purpose parametric object

modeling BIM design applications– Most are traditional B-rep modelers with a CSG-based

construction tree and a given library of object classes

• Where is the difference?– BIM allows for defining much more complex structures of object

families and relations among them without programming.

• Example of construction-level modeling– CADPiple and CADDUCT developed on AutoCAD Architecture– Autodesk MEP (not Revit MEP)– Autodesk Architectural Desktop (before Revit Architecture)– Works well for a fixed set of object classes to be composed

using fixed rules.


Predefined base objects • A set of predefined parametric object classes to

reflecting target functionality – To capture the standard conventions in the area of building that

the application targets

• Handbooks to address standard practices– Reflect industry conventions

• Address safety, structural performance, material attributes, etc.

– Examples:• Architectural Graphic Standards (Ramsey and Sleeper, 2000)• Detailing for Steel Construction (AISC 2007)• PCI Design Handbook (PCI 2004)

• Base objects in each BIM tool is a representation of standard practice interpreted by software company’s software developers.


User-defined parametric modeling • Predefined objects do not address everything

– Different shapes or behaviours, or objects that even do not have a class in the BIM tools, for example photovoltaic systems.

• Options of customization – Define in another system then import

• Without local editing capabilities

– Manually model using solid modeling geometry• Manually assign/update attributes

– Define a new parametric object family• Support automatic updating behaviours, but may not related to

other objects

– Define an extension to an exiting parametric object family• Modified shape, behaviours, and parameters• Fully integrate with the existing base/extended objects

– Define a new object class


Agenda








BIM environments, platforms, and tools

• Many kinds of available BIM software– Parametric modeling applications for generating

design information and possibly for structuring and managing information

• 10-50 BIM applications in large firms to support BIM technology

• System relations between BIM applications, in terms of– Their scope and functional difference– Interfaces to other applications– Multi-user environment


BIM tool

• A Task-specific application– Produce a specific outcome

• Examples: model generation, drawing production, specification writing, cost estimation, clash and error detection, energy analysis, rending, scheduling, and visualization.

• Standalone outcomes (for example rendering drawings or energy report) or outcomes for other application tools (for example models for structural analysis or data for fabrication).


BIM platform

• An application that generates data for multiple uses

• Usually for design phase

• Provides a primary data model to host most information on the platform

• Incorporate some tool functionality internally such as drawing generation

• Provides interfaces to multiple other tools


BIM environment

• Manage data from one or more information pipelines within an organization

• To integrate most or all BIM applications (tools or platforms)

• Track and coordinate communication between people as well as multiple BIM applications

• Capable to carry much wider forms of information, BIM-based or non-BIM-based such as video, image, audio, rich text.


Capabilities of BIM tools

• Model definition and drawing production in most cases for building modeling systems at tool level

• User interface– Consistency of menus following standard conventions– Menu-hiding feature– Modular organization of functionalities– Real-time online help

• Drawing generation– Quick visualization of model changes– Strong associations to support automatic drawing

updates


Capabilities of BIM tools (continued)• Ease of developing custom parametric objects

– Sketching tool for defining parametric objects– Ability to interface a new custom parametric object

into an existing class or family

• Complex curved surface modeling

• Other specific capabilities– Clash detection, quantity takeoffs, issue tracking,

incorporation of product and construction specifications, etc.


Capabilities of BIM platforms• Scalability: disk-based vs. memory-based

– This is the ability to handle combinations of a large project scale and modeling at a high level of detail.

• Library of BIM elements – More and more are available but little effort to

standardize the structure of object information

• Tool interfaces– How are different functions organized in a workflow.

• Platform user interface consistency– How to maintain the consistency of user interface

when BIM tools are shared and used by multiple platform users.


Capabilities of BIM platforms (continued)• Extensibility

– Whether a BIM platform provide scripting support and well-documented API for user extensions.

• Interoperability– How easy can data/models generated in one BIM

application be used by another.

• Multiuser environment– Multiple users to create and edit parts of the same

project directly from a single project file.– Not make much sense in a memory-based BIM

platform.


Capabilities of BIM environments

• 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 can be handled by a change flag or a timestamp that gets updated whenever an object is modified. The goal is to exchange and manage objects and sets of objects rather than files.


Agenda








Review of popular BIM platforms• Revit

• Bentley systems

• ArchiCAD


Revit• Best-known and current market leader for BIM

in architectural design

• Introduced to the industry in 2002 and current version is Revit Architecture 2013

• A family of products including Revit Architecture, Revit Structure, and Revit MEP


Revit as a tool• Easy-to-use interface, drag-over hints for each

operation

• Well organized menus and gray-out nonavailable actions

• Strongly associative drawing productions

• Supports new custom parametric objects and customization of per-defined objects

• Incrementally improved rule sets

• Current API provides good supports for external application development


Revit as a platform• The largest set of associated applications

• Some are directly linked through Revit’s Open API and other are through IFC or other exchange formats. – IFC = Industry Foundation Classes

• Many supporting applications– Structural, mechanical, energy and environmental, visualization,

facility management, and many others.

• Import models from SketchUp, AutoDesSys form•Z®, McNeel Rhinoceros®, Google™ Earth conceptual design tools.

• Support the following file 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 as an environment• Revit is a platform but not a BIM environment

• It carries object IDs, but version and change information is carried at the file level, not at the object level.

• This limits synchronization of objects with different views in different files.


Revit’s weaknesses• In-memory system

• Slow when >300MB

• Limited support for complex curved surfaces

• Lacking object-level timestamps, not provide needed support for full object management in a BIM environment.


Bentley systems• Bentley Systems offers a wide range of related

products for architecture, engineering, infrastructure, and construction.

• Bentley Architecture was first released in 2004.

• It runs on top of Microstation V8i.


Bentley as a tool• A standard set of predefined parametric objects

• Extension only available through the MDL API– MDL = Microstation Development Language

• Parametric Cell Studio module to support custom parametric objects

• Strong drawing capacities


Bentley as a platform• File-based system

– All actions are immediately written to a file and result in lower loads on memory

• Large array of additional systems, many of them were acquired to support its civil engineering products

• Some were acquired by purchasing small third-party companies and thus have only limited compatibility with others even within the same platform.– A user may have to convert model formats from one

Bentley application to another. 27/07/2013 Modeling Building Products and BIM Tools 87

Bentley as an environment• A well-developed and popular multi-project

server, called ProjectWise.

• Support replication of files to a prearranged set of local sites, managing the consistency of all files.

• Support Object IDs and timestamps


Bentley’s weaknesses• Large amount of products

• Take more time to learn and navigate

• Heterogeneous functional modules

• Different object behaviours


ArchiCAD• Earliest BIM application in architectural design

• First released by Graphisoft in the early 1980s– Nemetschek acquired Graphisoft in 2007

• Current version is ArchiCAD R17.0

• Support both Mac and Windows


ArchiCAD as a tool• Well-crafted user interface: smart cursors, drag-

over operator hints, and context-sensitive operator menus

• Strong coordination between the building model and drawings: every edit of the model is automatically placed in document layouts

• Drawing as reports (not bidirectional operations)

• Very broad range of predefined parametric objects, plus 31 external Web sites providing third party both static and parametric objects

• Versatile capabilities: site planning, interiors, space planning, etc.


ArchiCAD as a platform• Links to multiple tools in different domains.

• Some are direct links through Geometric Description Language (GDL), others through IFC

• Many supporting applications– Structural, mechanical, energy and environmental,

visualization, facility management, etc.


ArchiCAD as an environment• New DELTA Server

– To address file exchange and design coordination– Track reads/writes to its BIM Server repository

• Greatly reduce the size of updates by passing only modified objects to the server– Using Object IDs and timestamps


ArchiCAD’s weaknesses• Minor limitations in its custom parametric

modeling capabilities

• Also an in-memory system– But effective ways manage large project by using its

DELTA Server


Agenda








Lightweight applications• Not for creating or editing building models, but

rather for “publishing” information to support various workflows.

• Just to package, distribute, and review the building model information

• Markup and query capabilities

• Two widely available applications– 3D PDF, developed by Adobe– DWF (Design Web Format), developed by Autodesk


Acknowledgement

• Some of the slides presented here are adopted from materials of – BIM courses offered by the Digital Building Lab at the

Georgia Institute of Technology, and/or– BIM materials presented at VICOSoftware website

Documents

2 Lecture 02