5d cad
TRANSCRIPT
5D CAD
Welcome to the new dimension of Computer Aided Design (CAD) software. Using mature 3D CAD applications with integrated data for time sequencing (schedules) and resources (costs) combine to provide for a true BIM (Building Information Modeling) process known as 5D CAD. Advantages over simple 2D or 3D programs make 5D CAD the future of the construction industry.
5D CAD combines the 1D of program data, the 2D of a design based upon the program requirements, the 3D of a building model with an integrated database of information about the building (commonly known as BIM - Building Information Model or a Virtual Building), the 4D of time scheduling or sequencing of construction, and the 5D of cost and resources to complete the construction of a building. Output from this process can also be used after construction for facility management to use the information over the entire life cycle of a building.
Why use the 5D CAD Process? The following items are a few points to consider;
Data integration keeps everything up to date Graphical interface allows for understanding designs & process Information integration reduces risks Quickly analyze alternatives of design and implications Data tracking from programming to punch list Integrated process keeps the owner in control Architecture, Engineering, and Construction processes combined into a single
environment See the Graphic Outline of the Process for the AEC Tools Integration - Click
Here
AEC Tools Integration
Introduction to 4D Research by Martin Fischer
Traditional construction planning tools, such as bar charts and network diagrams, do not represent and communicate the spatial and temporal, or four-dimensional, aspects of construction schedules effectively. As a consequence, they do not allow project managers to create schedule alternatives rapidly to find the best way to build a particular design. Extending the traditional planning tools, visual 4D models combine 3D CAD models with construction activities to display the progression of construction over time.
My research team has tested the usefulness of visual 4D models in planning the construction of a hospital, a university building, a commercial building, a Frank Gehry project, and a theme park. These cases have shown that more project stakeholders can understand a construction schedule more quickly and completely with a 4D visualization than with the traditional construction management tools. However, 4D models are very time-consuming to generate manually and cannot currently support analysis programs. The difficulty and cost of creating and using such models is currently blocking their widespread adoption. My research team has been formalizing the construction knowledge necessary to build 4D models and has developed a methodology that guides project planners in generating 4D models from 3D product models. We have demonstrated that this formalized knowledge enables project managers to create and update realistic schedules rapidly and to integrate the temporal and spatial aspects of a schedule as intelligent 4D models. These intelligent 4D models support computer-based analysis of schedules with respect to cost, interference, safety, etc., and improve communication of design and schedule information.
We've organized this site into seven areas:
1. Research Issues This page describes in detail the 4D research issues we are addressing and links to more extensive documents describing these issues.
2. Research Projects This page describes the 4D research projects at the Center for Integrated Facility Engineering, Stanford University
3. Papers & Talks This page highlights upcoming talks presented by members of our groups, the most recently published papers, and a full list of papers published by members of the 4D research group.
4. 4D Examples & Applications This page provides links to 4D examples from various projects.
5. People If you want to know more about the people in this group here's your chance.
6. Class Links This page provide descriptions of classes related with 4D modeling offered by the Stanford CEM program.
7. Related 4D Links This page provide links to commercial software vendors providing 4D tools, other research projects performing 4D work, and other research or industry links.
Wish List for 4D Environments: a WDI R&D Perspective
By Martin Fischer, Kathleen McKinney Liston, and the Paperless Design Project Team at Walt Disney Imagineering
This document outlines the functionality needed for a 4D environment to serve the needs of the Paperless Design Project at Walt Disney Imagineering (WDI). This report was originally written for Paperless Design Team members and Research and Development personnel at WDI to understand our "wish-list" of functionality needed to support 4D environments. This document has been edited to reflect a more general perspective. Ultimately, this document should serve as a roadmap for the development of next generation CAD, project management, and concurrent engineering tools. We do not envision that all the functionality discussed below needs to be provided in one product, but any products used in this process should provide the "hooks" to enable the representation and linking of the information required for 4D modeling.
The report is organized into the following sections:
1. Report Summary 2. Vision of 4D Technologies in AEC Practice 3. Paperless Design Project Goals and Process for Evaluating 4D Technologies 4. Description of 4D Modeling Tasks 5. Functionality Required to Perform 4D Modeling Tasks 6. Implementation Challenges 7. Appendix: Purpose of 4D Models and Modeling Issues
We welcome any comments or feedback on this report.
REPORT SUMMARY
Advancements in 3D technologies provide the opportunity to use 3D CAD models to view construction project information. Research projects at Stanford University and the Paperless Design Project at WDI are looking at how engineers and project managers can utilize 3D and 4D CAD to:
manage and minimize risk throughout all stages of a construction project
effectively communicate the design, schedule, and other project data
rapidly explore design and construction alternatives
The initial phase of these projects involved the evaluation of 3D and 4D commercial and prototype technologies to determine the benefits and limitations of these technologies. The goal was to define a vision of:
the use of these technologies to support the design and planning of construction
projects within the WDI organization
the architecture and functionality of next-generation 3D and 4D technologies
This report describes the results of the initial evaluation of the use of 3D/4D technologies for the planning of a WDI construction project. Some of the specific benefits of the 3D/4D modeling process realized to date are:
clear communication of the sequence of construction to all project participants
improved understanding of design and schedule
ability to receive feedback from a broad range of project stakeholders
The limitations of current 4D technologies are:
slow generation of alternatives
no computer-based risk analysis
minimal integration with other project data
Based on this initial evaluation, the Paperless Design Team has compiled an initial "wish-list" of functionality that is needed to address these limitations and support long-term project goals. This functionality wish-list is organized into three areas and are summarized:
Functionality needed to Generate and Manipulate Model-Based Project
Data, specifically functionality to:
o generate and manipulate object-models of the construction project
o generate and manipulate associations between those objects
o take apart and re-organize the project model
Functionality needed to Represent Model-Based Project Data, specifically
functionality to:
o represent the 4D model as a set of objects
o maintain multiple representations of a project
Functionality needed to Visualize Model-Based Project Data, specifically
functionality to:
o view the object-models in a real-time 3D environment
o view project data and relationships between project data within the 3D
environment
o provide a "4D viewer" accessible to all project participants
The remainder of this report elaborates this wish-list and the rationale for needing this functionality. We first describe the vision of 4D technologies and summarize the 4D modeling process performed during the Paperless Design Project. We then explain how planners perform 4D modeling tasks today, i.e., how they generate, update and maintain, and visualize and distribute 4D models, and outline how we envision planners will perform 4D modeling tasks in the future. We then discuss the functionality that is needed in a next-generation 4D environment to support these tasks. Finally, we conclude with the challenges we face to implement this functionality.
2. Vision of 4D technologies in AEC Practice
Planners, designers, and engineers will use 4D technologies to analyze and visualize many aspects of a construction project, from the 3D design of a project to the sequence of construction to the relationships between schedule, cost and resource availability data. Planners will create, update and maintain, and deliver a 4D object model throughout a design/construction project. The 4D technologies will enable planners to generate various views of this 4D object model to clearly communicate the spatial and temporal aspects of construction schedules to all project participants. 4D technologies will no longer be used to simply animate the sequence of construction but will be used to communicate a wide range of project data much more clearly and efficiently than possible today. Planners, designers, and engineers will use 4D environments to visually relate data much like the way engineers use gradated color 3D models to visualize the stresses on structures.
This vision implies that 4D technologies will provide a view of a project database. This project database will store and maintain the representation of building components and construction activities, their inter-relationships, and relationships to other project data. This database will be designed to support concurrent engineering of the facility and its delivery process by supporting multiple representations of project data, multiple ways of organizing and relating the data, domain-specific views of the data, and standard representations of these data so that multiple applications can interpret the data. This project database will not only support the use of 4D technologies throughout the project life-cycle but also support other design and construction technologies (Figure 1).
Figure 1: Vision of Project Database showing a shared database that stores project components that are generated, accessed, and organized into multiple
project models and views
To fully maximize the benefits of 4D technologies, planners, designers, and engineers will need to change how they produce project data. They will focus their efforts on producing
and evaluating "models" instead of drawings. To build 4D models that accompany a project throughout its design, planning, and construction phases, users need to be able to take these 3D models apart and put them back together quickly and in very flexible, interactive ways. They need to represent the design not only as graphical drawing objects, but also as intelligent and open information objects that can be linked to other project information. Today’s CAD tools are mainly focused on the production of construction drawings and do not offer the functionality needed for 4D modeling. They do not offer an intuitive and easy-to-use object-oriented environment that allows users to build a graphical and informational model of the project that can be taken apart and put back together in new ways, and that can be shared easily with the various disciplines involved in the project life cycle.
3. Paperless Design Project Goals and Process for Evaluating 4D technologies
The goal of the first phase of the Paperless Design Project was to understand the issues with respect to using 4D technologies and to propose a plan for implementing 4D technologies in the short and long-term. This includes specifying the contents of a project database from the 4D perspective and specifying the functionality for generating and accessing the content in the project database (Figure 2). Future projects within R&D at WDI will consider the structure and contents of the project database from other perspectives. Much of the functionality needed to support 4D technologies, however, are needed to support other design technologies.
Figure 2: Focus of Paperless Design Project
The Paperless Design Project Team selected a construction project that presented potential construction problems due to the complexity of the site. The project team included representatives from the design team, construction team, virtual reality group, 4D consultants, and CAD analysts. The goal of the team was to produce a 3D and 4D model of the selected construction project for visualization in a Virtual Reality Cave, on the desktop, and in a web-browser (Figure 3).
During the three-month project, commercial and prototype technologies were used. The 3D models were produced by modelers in the VR group who were most proficient with Alias Wavefront and Multigen. These tools also enabled the most efficient transfer of the 3D model into the Cave environment.
Following is a brief description of the various 4D modeling processes performed.
1. Production of 4D model using commercial tools 2. Generation of a 4D model using commercial tools and customized add-ons 3. Generation of a 4D model using prototype tools
Figure 3: Inputs, Outputs, Controls, and Tools for Paperless Design Project
3.1 Production of 4D model using commercial tools
The first 4D modeling process utilized commercially available software: Alias Wavefront, AutoCAD, Primavera, and Jacobus Schedule Simulator. This process involved the following steps (See Figure 4):
1. Generating the 3D model in Alias Wavefront 2. Breaking the 3D model into twenty-three "chunks" to represent the construction
breakdown of the project 3. Exporting these chunks from Alias as DXF files
4. Importing the twenty-three DXF files into AutoCAD5. Organizing the components in each file into two layers. One layer represented the
structure and another layer represented the spaces in between the structure and was used to represent the "torquing of the structure."
6. Merging all of the DWG files into one drawing 7. Exporting the single DWG file as a "JSM" file or Jacobus 3D model file.8. Importing the JSM file into Jacobus9. Importing the schedule file (generated in Primavera) into Jacobus10. Linking the CAD components to the schedule activities to generate the 4D model11. Playing the 4D model within the Jacobus environment
This process was tedious and presented the following problems:
project participants could only view the 4D model within the Jacobus environment,
unless screen captures were made of each day or specified period/time.
the 4D model information could not be transferred to the cave environment
most updates to the 4D model required starting at step 1
Figure 4: 4D Modeling Process with Commercial Tools
3.2 Generation of a 4D model using commercial tools and customized add-ons
The second process utilized commercial tools with add-ons. These customizations were:
a visual-basic macro in Excel. This macro creates a dialog box that lists
construction activities and lists 3D components (from 3D Studio Max) and enables
the planner to manually link one by one the activities and components or
automatically link components and activities.
a set of MaxScripts in 3D Studio Max. These maxscripts take information sent
from Excel and create animation information. For example, a message is sent
from Excel to set the start and finish dates of a particular component. The
maxscript creates animation keys to turn on the visibility of the component at the
start date and animation keys to change material attributes of the component to
reflect its state of construction, e.g., making the component red for the duration
of its construction.
This process involved (Figure 5 and detailed here):
1. Exporting the AutoCAD file created in step 4 of the first process to 3D Studio Max2. Exporting the schedule information from Primavera to Excel3. Manually listing the name of the CAD component associated with each activity in
the Excel spreadsheet4. Running the macro within Excel to import the list of 3D components from 3D
Studio Max and generate a list of the construction activities 5. Linking the activities to 3D components6. Rendering the 4D visualization in 3D Studio Max7. Exporting the Excel data in ASCII format to the CAVE
This process had the following benefits:
the 4D visualization was fully-rendered
all project participants could view the 4D visualization because the movie file
could be posted on-line in Quicktime or AVI format
and the following problems:
any changes that had to be made required performing the entire set of 4D
modeling tasks again (starting at Step 1, Process 1)
the ouput was not fully interactive. Although planners could change the temporal
state of the 4D visualization the planners could not interact with the spatial data,
e.g., change the viewpoint of the visualization.
Figure 5: 4D Modeling Process with Commercial Tools+
3.3 Generation of a 4D model using prototype tools
The third process involved developing a set of 4D prototype tools. These included:
a Java 4D Application . This application provides the functionality to import the
names of CAD components and schedule information, link activities to CAD
components, and save and update the 4D model.
a Java 4D Applet that communicates with a VRML world in a web browser. This
applet provides the functionality to interactively view a 4D visualization in a
browser.
a Java3D application. This application provides the functionality to
generate, view, and store the 4D model in a desktop environment.
Cave 4D functions. These functions provide the functionality to import
the 4D associations exported from the Java 4D application and to use
these associations to view the 4D visualization in the cave.
The 4D modeling process with these tools involves (Figure 6):
1. Importing the schedule data into the Java 4D application2. Importing the CAD data into the Java 4D application3. Organizing the CAD data into approriate groupings (if needed) 4. Linking the components to the activities5. Assigning "action-types"6. Exporting 4D model to CAVE and to Java 4D applet
The process had the following benefits:
updates and changes could easily be made without re-performing the entire 4D
modeling process
re-grouping of CAD components is possible within the 4D environment
on-line viewing is possible in the 4D environment
and the following problems (Figure 7):
data is in ASCII format
links to original data are not maintained
schedule is not hierarchical
Figure 6: 4D Modeling Process with Prototype Tools
Figure 7: Diagram showing Current Process and Current Problems
4. Tasks to Generate, Visualize, Update, and Distribute 4D Models
The execution and evalution of these processes as well as our experience gained on other 4D modeling projects at Stanford University allowed us to develop a set of 4D modeling tasks and outline the corresponding functionaliity. These tasks and the related functionality are presented next.
In this section we describe the 4D modeling tasks planners can perform today with commercial 3D and 4D tools, contrast those with how we envision planners performing 4D modeling tasks, and describe the functionality 4D technologies need to provide to support these tasks. We have organized these taks into three main groups of tasks:
1. Tasks to Generate and Manipulate 4D Models 2. Tasks to Visualize and Evaluate 4D Models 3. Tasks to Deliver and Distribute 4D Models
4.1 Tasks to Generate 4D Models
Today, the generation of a 4D model involves three main tasks, which we elaborate in the following sections:
1. generating a 3D model that represents the spatial aspects of the construction project at the appropriate level of detail
2. generating a schedule3. relating components in the 3D model with components in the schedule
4.1.1 Generating a 3D model
Today
A 3D model that is used in a 4D model is different in organization and content from a 3D model that architects or engineers use for visualization or analysis. Typically, designers organize the components in a 3D model according to corporate or AIA layering standards that focus on arranging the graphic information in a way that facilitates drawing production. This drawing organization is usually not useful for schedule visualization in a 4D model because the layers rarely correspond to the geometric information that describes the scope of a (construction) activity. Since today’s CAD tools display geometric information by layers (i.e., everything on a layer is either shown or not shown) it is important that there is at least one layer for each activity. It is easy to link several layers to one activity, but linking several activities to one layer will not result in a 4D visualization at the level of detail in the schedule.
Additionally, the 3D CAD model typically contains only the final, physical components of a facility. During construction, many other components, such as scaffolding, laydown areas, etc., are needed. Often, necessary detail is also missing in the 3D model. To set up the 3D model, planners have to add these components to the model. In summary, planners need to perform the following tasks and subtasks to set up the 3D model:
(a) Organize the 3D model into the "3D chunks" or work elements necessary to match the level of detail in the schedule. This involves:
i. Placing the geometric information in one layer onto two or more layers. This is necessary when, e.g., all steel columns on one floor are on one layer and the schedule calls out two activities to install the columns (one to build the columns on the East side and another to build the columns on the West side). We envision a graphical interface that would allow users to pick components and assign them directly and easily to a new or different layer.
ii. Regrouping CAD components found on several layers onto a different set of layers. A drawing might organize mechanical information by type of duct on a floor, but the schedule might show activities that install mechanical ductwork in a zone on a floor regardless of its type. The same tool functionality as in (i) should work here as well.
iii. Breaking a component into smaller pieces and putting the pieces on separate layers. This is necessary when there is just one component in the CAD model (typical for slabs, walls, roofs), but the component is built in several phases (e.g., three concrete pours for a slab). We envision a graphical interface that allows the user to cut a larger component into smaller components in a manual or parameter-driven way. In the manual way, users would, e.g., drag lines across a slab component to indicate slab sections. In the parameter-driven way, users would specify (or rules would infer) parameters needed to break up a component, e.g., cut a slab into 3 pieces or cut a slab into pieces with no more than 100 m3 of concrete in each section.
(b) Add construction-specific components (e.g., scaffolding, cranes, access roads, laydown areas) that are typically not included in the CAD model during the design phase of a project. This involves:
i. Adding detail to components, e.g., adding reinforcement objects to a concrete component.
ii. Adding temporary components, such as scaffolding, equipment, and shoring.
Future
Organizing and adding this information is tedious and makes the 4D modeling process infeasible for most planners. Future 4D environments need to enable a much more flexible way of organizing the 3D model and adding construction-specific information like construction areas and zones. Future 4D environments will enable planners to:
(a) Organize 3D model components into a hierarchical, construction focused view of the model. This involves:
i. organizing the 3D model into construction areas or zonesii. organizing the 3D model components hierarchically to reflect
levels of detail
(b) Add construction-specific content from construction component and method libraries. This involves:
i. selecting construction components from libraries, e.g., equipmentii. applying algorithms to components to automatically generate
detail such as reinforcemen
4.1.2 Generating a Schedule
Today
Today, schedules are generated in a schedule tool such as Primavera or Microsoft Project. Planners are familiar with these tools and the functionality they provide. The generation of a schedule for use in a 4D model involves the traditional scheduling tasks such as:
generating and naming activities
assigning durations to activities
sequencing activities
as well as:
ensuring that the schedule is at a level of detail appropriate for the
desired 4D visualization
assigning "action-types" to activities, i.e., temporary, deconstructive,
constructive. These action types define how the components are shown in
the 4D visualization, e.g., a temporary activity implies that the
components associated with that activity are made visible at the start of
the activity and then made invisible or turned off at the end of the
activity.
Future This traditional way of generating a schedule limits the potential benefits of a 4D model. First, this process does not utilize the 3D description of the project. When schedulers create activities they usually have a mental picture of the physical scope of the activity. They have no way today, however, to translate their thinking directly into activities that are linked to 3D components that represent the physical scope of work. Instead, they must create an abstract activity and later link the activity to its related 3D CAD components. We envision a tool that allows schedulers to create activities and a schedule in a 4D environment that
includes an interactive 3D view of the project. Planners will be able to:
(a) Generate the traditional schedule content within the 4D environment, thus directly associating the activities in the schedule with the 3D components. This includes:
i. delineating the scope of an activity in the 3D model and in the hierarchical 3D model (if available).
ii. using drag, point and click, cutting planes, etc. to select 3D CAD model components that represent the physical scope for a new activity (some of the same functionality as outlined in 4.1.1 is useful here)
(b) Use 3D information to calculate activity durations. This includes:
i. extracting quantity information from CAD components (automatically match units of measurement of quantity information to the units required by the production rate)
ii. finding appropriate production rate information in database (possibly with user help who specifies the type of resource or crew used) or ask user directly for applicable production rates.
(c) Automatically generate schedules from the 3D model.
(d) Define non-temporal and temporal relationships between activities. Traditional schedules do not represent how spatial relationships between activities affect the construction sequence.Today’s scheduling software supports the representation of relationships that model the temporal sequence of activities. Hence, all sequence relationships have to be abstracted to a temporal relationship, even though the reason for a sequence relationship might be a spatial constraint (e.g., access to a certain area of a project might be constrained by other activities that are occurring nearby).
(e) Define and classify "action-types". The current set of action-types needs to be expanded to support various types of actions. In some cases, a component is acted-on in multiple ways and current commercial tools do not enable clear communication of multiple types of actions. For example a concrete wall component may be associated with several activities, such as "pour concrete", "cure", "finish","paint", etc.
4.1.3 Relating 3D model Components to Construction Activities
Today
Today’s 4D tools (Intergraph’s Schedule Review and Jacobus’ Schedule Simulator software) require the manual linking of CAD layer names with activity names or the use of a pre-defined naming convention for activities and CAD layers so that the 4D software can create the links between CAD layers and activities automatically. Planners need to perform the following tasks:
manually link a CAD "container" (layer, object, group) to an activity or set
of activities
create rules to link 3D CAD components to activities
Future
While this functionality is helpful, it does not provide the flexibility and intelligence necessary to associate the activities and CAD components quickly and to maintain these associations over the life of a project. In the future, planners will:
(a) Define 4D associations in various ways. The association between 3D components and activities can be based on many reasons and planners need to be able to define:
i. User-driven associations. Users should be able to associate CAD components and activities through lists of names (as supported today) or hierarchies, or by pointing to and clicking on graphical representations of activities (e.g., bars in a bar chart) and 3D components.
ii. Name-driven associations. Users specify a rule that uses the names of CAD layers (or objects in the future) and the names of activities to create the appropriate links (as supported today). For example, many projects have naming conventions for activities in P3 (Primavera), and if the same naming convention is used to name the CAD layers, the software can automatically link an activity to its corresponding CAD layer(s).Association by responsibility.The reason for a link could be that a particular firm or superintendent is responsible for a particular activity in a particular area.
iii. Association by method. The reason for a link could be based on the characteristics of a particular method of construction.
iv. Association by x. Similar to (iii) and (iv), associations can be based on other reasons.
(b) "Record" or document the reason for associating a particular CAD container (layer, group, component) with an activity. Without representing the reason for an association in the 4D model it becomes very difficult to maintain the associations as the 3D and schedule models change. It also becomes nearly impossible for someone other than the original creator of the 4D model to update and change it because the reason for a particular association is missing (even though the creator of the link had to think about the reason at the time the association was made). The tools will need to provide functionality to:
i. Manually enter rationale.ii. Infer rationale.
(c) Interactively generate 4D associations with 4D macros or methods. This includes:
i. Copying and pasting 4D associations between similar components and activities
ii. Recording assembly sequences. Instead of defining 4D associations by linking components and activities, a planner could perform the assembly sequence within the 4D environment, and the 4D tool would record the assembly sequence in a much more interactive way, similar to how today's recording macro features work.
4.2 Tasks to Update and Maintain 4D Model
Today Throughout the construction project planners, designers, and engineers must update and maintain the 4D model as design or schedule changes occur. Since no 4D tool provides a direct link to the 3D model and the schedule content, users have to access and edit the original content and re-perform many of the 4D modeling tasks. This typically involves:
regrouping 3D model components to match a different activity breakdown
(more or less detail, different scope)
changing activity durations
resequencing activities
re-exporting and importing the 3D model data and the schedule data
reassociating 3D model components with construction activities
Future
In our experience, it is very cumbersome and difficult to update and maintain a 4D model because the reason for the creation of activities, their associations with CAD components, and their sequence relationships is not made explicit and stored with the 4D model during the creation of the 4D model. Without intelligent hierarchies of components and activities and without explicit criteria (reasons) represented in the 4D model, the user has to recreate the thinking process that went into creating the model and must make all the changes manually.
Capturing the rationale of the 4D model (as described in 4.1.3b) is only half the challenge. Updating 4D models also involves managing the impacts of changes. With a hierarchy and with explicit criteria for the existence of objects and their links, users can invoke computer algorithms that change a 4D model locally or globally, i.e., the computer algorithms do all the tedious work of deleting activities and their links and associations, creating new ones, etc. In the future, planners will be able to:
(a) Make local and global changes
(b) Utilize rationale to manage 4D model changes
4.3 Tasks to Distribute and Visualize the 4D Model
Today Today, planners do not have many options for distributing and visualizing the 4D model. Any project participant wishing to view the 4D model must either own the 4D software or view a "saved" 4D visualization in movie mode. Thus, planners must distribute 4D visualizations either
within a 4D environment that allows the planner to change the temporal
and 3D state of the 4D visualization but requires each viewer to own the
4D application or
in movie-mode (example), such as a videotape, that does not allow the
planner to change any aspect of the 4D visualization but allows any
project participant to view the 4D visualization
Figure 8: 4D Visualization Today
Future
We imagine that planners will disseminate 4D models with local and wide-area networks as well as with traditional sneaker net methods such as floppy disks and CD-ROMS. Since one of the biggest value of a 4D model is its ability to visualize and communicate a schedule clearly it should be easy for people who just need to see the information to view a 4D model on their desktop. Hence, the output should be displayable in commonly available software (e.g., a web browser). In the future, planners should be able to:
(a) Distribute interactive 4D visualizations to all project participants, that enable them (project participants) to:
i. view the models in a "view-only" interactive real-time 3D environment, e.g., rotate, zoom, walk-through, change viewpoints, change render-modes
ii. customize the views (e.g., level of detail, area of focus) for recipient iii. view multiple alternatives of the schedule simultaneously
(b) Visualize other information related to the 4D visualization, e.g., procurement status, weather data, cost and resource data (See Figure 8 and examples)
(c) Red-line the 4D visualization to highlight problems or propose changes
Figure 8: Example of Future 4D Visualization
5.0 Functionality
This vision of the kinds of tasks planners will be able to perform with 4D technologies requires functionality in three areas:
1. Interaction: Generating and Manipulating 4D models2. Visualization: Viewing 4D models3. Representation: Storing 4D models
5.1 Interaction Functionality
Next-generation 4D technologies will enable planners to generate 4D models in a more interactive way. Planners will continue to generate 4D models from existing 3D models and schedules as well as generate schedules interactively within the 4D environment or automatically generate a schedule from a 3D model. 4D tools need to support a variety of interactions with the 3D model content, the schedule content, and the relationships between that content and other construction project data. Specifically they need to provide the following types of interaction functionality:
(a) 3D model interactions:
Rotate and move viewpoint(required because, as the project gets built in the
4D visualization, parts of the 3D model that will be built later might become
obstructed by already constructed components)
Zoom (required because a schedule and 3D model might be at different levels of
detail for certain time frames, or the user might be interested in more or less
detail for a particular time frame)
Turn classes of objects on and off or make them transparent during a 4D
simulation (this is important for buildings, e.g., where the installation of slabs and
roofs obstructs the view of the construction activities that go on inside)
(b) Schedule interactions:
Support the typical temporal sequence relationships (finish-start, start-
start, finish-finish) between activities and lag times for the relationships.
Change activity dates. For example, a user should be able to slide an activity
bar and see the repercussions of changed start dates on other activities,
milestones, and space needs.
Adjust activity durations (required because a contractor might add or take
away resources to adjust activity durations as necessary, or the initial production
rate assumptions might have been too high or too low).
Resequence activities (change the schedule logic in the bar chart, network or
object view). This is required because materials might be delivered early or late,
necessitating the development of new 4D alternatives that minimize the impact of
this schedule change. The 4D model should help assess the spatial (e.g.,
availability of access and work space) and temporal implications of schedule
changes, thus limiting the need for further schedule changes due to oversights
when making the first schedule changes.
Enter activity name. The tool should offer a default activity name based on the
name(s) of the components.
Propose default relationships for a new activity (e.g., to its neighboring
activity of the same type, to the activity that acts on the components below).
Support the specification of spatial constraints or relationships between
work elements (e.g., specify that an activity should always be 100 m ahead of a
succeeding activity).
Link lag times to spatial areas to represent lag times as spatial constraints
(e.g., concrete in a certain area needs to cure, or no other activity should be
within 50 m due to safety concerns). We envision that the user can again use the
graphical models to specify these relationships or work with the (hierarchical) list
of names.
(c) 4D model interactions
Link several components to an activity.
Link several activities to a component.
Do not restrict the linking of activities and components to certain
branches of the component and activity hierarchies (if those exist), e.g., it
must be possible to link two components from different branches of a hierarchy to
an activity.
Capture the rationale for the 4D associations, either through manual
processes or intelligent construction "agents."
Allow the user to enter other information for the newly created 4D
object (an activity linked to a 3D component), such as information about the
reason for the association
Regroup the activities and 3D components. Initial assumptions about weekly
or daily progress might be off, now requiring or allowing a smaller or larger buffer
or lag between activities in a work sequence, which in turn requires a new
grouping of activities and 3D entities, since the scope for the activities has
changed. The software needs to highlight the physical scope of work for an
activity or a set of activities in the 3D model and allow the user to change the
associations between 3D components and activities in the object or graphic view.
Switch between and display several levels of detail. This requires that the
graphical views of the schedule and CAD models adjust themselves depending on
the level of detail chosen by the user.
Attach other types of data, e.g., cost for activities, and corresponding
visualization mechanisms, e.g., S-curves that can be displayed as the 4D model is
running.
5.2 Visualization Functionality
One of the key parts of our vision is that planners will be able to visualize many aspects of the construction project within a 4D environment. In the following table we list the types of content that planners need to visualize and the correlating functionality that 4D technologies need to provide to support the visualization of that content. We also list some of the challenges in implementing this functionality.
Table 1. Examples of additional information a 4D model could display.
Visual Content Needed Visual Functionality Challenges
Explanation of activity sequencing
text displayed as schedule is
"running" (or scrolling)
text on demand (when user
clicks on a sequence
relationship in a schedule
window)
at any given time, many sequence relationships will be active, hence the computer will need to decide which explanations to display
Schedule
UI for visualizng Gantt chart
or other schedule views
(CPM)
Responsibility for work
reorganize schedule by
responsibility
use specific colors in 4D
visualization
there are many contractors on a project, and a color scheme might quickly become confusing
Work areas
add a 3D element showing
the work spaces needed for
installation (crew and
equipment), delivery
(access), protection, etc.
each 3D component will have several associated work areas, hence the visual model could quickly become cluttered
Cost
running total (numbers) as
time progresses
break down material, labor,
overhead (and other costs)
as desired
S-curve
working capital needed
(inflows vs. outflows)
calculate NPV as schedule is
changed and needs for
working capital change
accuracy of cost estimate (based on 3D/4D model or based on an independent estimate)
Weather text showing
high/low/average
temperature for date and
location of project (or any
other important location)
curves displaying climatic
information
Analyses of 4D model
highlight problem area as
schedule simulation is
running (blinking, bright
color, ...)
list all problems discovered
in the 4D model and provide
a hyperlink to the relevant
portion of the 4D model
the level of detail in model determines the conflicts and problems that can be found and shown
Two schedules: same schedule, but different level of detail
two windows showing the
two schedules, with a box
indicating the scope of the
detailed schedule in the less-
detailed schedule
Two schedules: different schedules, but same level of detail (e.g., as-built, as-planned, as-revised, as-proposed, etc.)
probably need two different
4D models, since the scope
of the 3D model and
schedule might be different,
and time of construction for
components will be different
between the two versions
how to contrast, highlight similarities, differences between schedule (4D model) versions
Multiple viewpoints of 3D model use two windows
5.3 Representation Functionality
The representation functionality needs to support the interaction and visualization functionality described above. Additionally, the representation functionality needs to support the distribution and integration of data from multiple sources. Much of this functionality depends on 4D models that are object-oriented and are generated from standard libraries of project components. Current standardization efforts such as the International Alliance for Interoperability (IAI) are a good starting point for developing standard representations of project components that are needed for intelligent 4D models. However, the current Industry Foundation Classes (IFC's) were not designed to
support the functionality discussed in this report. Thus, the IFC's need to be extended to support:
representation of 4D associations
representation of non-temporal relationships between activities
6.0 Implementation Challenges
Implementing this wish-list of functionality is a challenge due to the current make-up of software in the AEC industry. There are no standard representations of 3D CAD components, construction activities, and no standard communication protocols between programs. Thus, at a functional level, creating relationships between data in a useful and accessible way is a formidable task. At a conceptual level, the conceptual framework of these tools also precludes implementing robust 4D technologies that support large complex projects. In this section we highlight some of these functional and conceptual limitations.
Functional Challenges due to Current Make-Up of AEC Software
To overcome these limitations, there might be work-arounds or options already available today, which are unknown to us. In some areas, especially when we make reference to the new Architectural Desktop software, the discussion is based on a very limited understanding on our side of the available functionality, and we are offering our thoughts based on the demonstration we saw at Autodesk on August 21, 1998 and our ten years of experience with object-oriented software.
1. The current representation of building components is geometry-based, inaccessible, and not customizable.
Today, the only way to access "objects" in AutoCAD is through ARX or VB. This route allows us to access limited information about objects in the CAD model and to create new objects with attribute information. Unfortunately, these options do not enable the user to create a true 4D object model since the relationships between CAD objects in AutoCAD and activity objects must be generated and stored in a separate application. For example, standard building component classes can be extended as well as new ones created. However, the current object model in AutoCAD focuses on geometric attributes. It provides insufficient support to define relationships between components and activities, and it is not straightforward to access all the information about an object. In particular we need to be able to create and access methods that enable us to relate these components to construction activities. In summary, we need object-oriented representations of components that are customizable, editable, and accessible.
2. Models are not hierarchical.
AutoCAD allows the designer to create one breakdown of the geometric information into a set of layers. As mentioned throughout this document, this one breakdown is not sufficient to support the multiple perspectives on the 3D model necessary for 4D modeling. Furthermore, the layers give the user only an "all or nothing" option to display geometric information. Users do not always want to see all the detail, and they need to be able to reorganize the information that is shown
and that can be selected and grouped. A hierarchical model would enable users to work at the appropriate level of detail, i.e., instead of either seeing all or none of the information they could now select the desired level of detail. Users should not be restricted to work at the same level of detail for all parts of the 3D model. For example, they should be able to work at the most detailed level for the foundations in a certain area of the project and view the other foundations and the structural system with less detail. This would allow them to see the context of their current work without their desktop being cluttered with unnecessary graphical objects. The "drawing methods" that are part of objects in Architectural Desktop allow a user to customize the display of geometric information to some degree. However, because the detail is generated by methods that are part of a particular object it can become difficult to generate views and groupings of the detail from a perspective other than the parent object. For example, a footing object might have a method that displays the footing as a simple 3D box in one view and with the reinforcement and formwork detail in another view. While this enables a user to show detail in some areas and hide it in others it makes it difficult to collect and group all of the footing reinforcement between gridlines A and G for association with a construction activity. In the example, the user wanted to switch the view of the information from a footing perspective to a reinforcement perspective. A hierarchical, fully object-oriented decomposition of the 3D objects would give users more flexibility to create, interact, and manage information about a project.
3. Views of models are mainly graphical.
In addition to the graphical view of the model, users should be able to navigate the component hierarchies easily. They should be able to inspect the graphic and information content of a CAD model and its components. They need to be able to browse the hierarchy and click on an object or group of objects and see the graphic model and bring up a list of all the objects’ attributes and relationships. Architectural Desktop begins to address this limitation.
4. It is difficult to convert AutoCAD files to a real-time 3D environment.
Currently, text files are the only option to export an AutoCAD model to another application. Today, we need to export the 3D AutoCAD model to other applications because of limitation (1) and because of the need to work in an environment that renders objects in real-time. It is difficult to export more than the graphic geometry, which then makes it extremely cumbersome to manipulate the 3D model for 4D modeling. An open and more accessible hierarchical object model is needed that facilitates the exchange of the graphic and information content of a 3D model and its components. The hierarchy and all other information needs to be maintained when the files are exported to other applications.
Conceptual Challenges:
Interaction Challenges:
interaction "metaphors" to interact with 4D models (e.g., for red-lining)
development of a general tool set that supports project-specific work
Representation Challenges:
who owns the project database and who develops the project database
how to utilize and extend current industry standard efforts such as STEP and IAI
Visualization Challenges
whether the display needs to happen as the 4D simulation/visualization
progresses
whether an asynchronous display is feasible and acceptable
to what extent the display should be user-selected or system-driven
large displays vs. desktop displays
Appendix – Purpose of 4D Models and Modeling Issues
Since a 4D model combines the designers and builders perspective it supports concurrent engineering of the facility design and its delivery process. This appendix gives a few specific examples of purposes for 4D models and lists common modeling issues.
A1. Purpose of 4D model in Construction and Construction Planning
Given the time pressures of many projects today and the limited space typically available on site, the overall goal for the 4D modeling process is to create a dynamic 4D model that allows project management to resequence activities rapidly when necessary while reducing the risk of running out of space. Hence the 4D model should allow users to play with and respond to scenarios like the ones listed below. These are examples of decisions a 4D model should support and insights it should provide.
Communicate schedules clearly to all stakeholders to ensure that
everyone is on the same page and to solicit everybody's input in a timely
fashion.
Try different activity sequences to lower risks of delays and
unproductive work.
Show relationships between on-site and off-site production and make
sure that on-site production needs are communicated clearly to off-site
fabrication centers.
Respond to availability problems of pre-assembled steel components. If
supply of pre-assembled components differs from that required in the
schedule activities need to be rescheduled to understand the
ramifications on space use.
Determine overlap possible and necessary for crews and work. E.g.,
show the relationship between foundation work and structural work.
How far ahead of the vertical steel erection should the footing and steel
column work be so that the crews and equipment do not hinder each
other and affect the work in adjacent areas? Issues to consider are the
required and achievable early concrete strength of concrete footings
which determines curing time for footings and the minimum lag time to
vertical steel erection, quantity of vertical steel to be erected in each
area before torquing and bolting, access needs for other work, etc.
Ensure that laydown areas will be available close to the location offinal
installation for each discipline without hindering the work of a discipline
and other work.
A2. Modeling Issues
It is important to agree on the appropriate time step (i.e., should the
schedule simulation show construction month by month or week by
week) so that the schedule and CAD models are prepared at the right
level of detail.
Determine a time frame or a project area where construction is likely to
be particularly complex and difficult to schedule. Identify the worries of
project managers. This will help in determining the level of detail
needed in the CAD and schedule models. With today’s CAD tools it is far
easier to combine detail than to add detail. Hence our recommendation
at this point is to err on the side of too much detai for initial model
building.
Discuss level of visual detail in model. For construction simulation, the
CAD model does not necessarily have to contain a lot of visual detail.
Hence, the 3D CAD model can often be simplified in comparison to an
architectural 3D model if the sole purpose of the model is to support a
4D modeling effort.
4D Research Projects
At the Center for Integrated Facility for Engineering, Professor Martin Fischer has lead research projects related to 4D CAD since 1994. The first project, sponsored by Dillingham Construction and performed by Eric Collier, involved the development of a 4D model to communicate the four-year construction project of the San Mateo County Health Facility. Due to the success of this project, Martin Fischer continued to pursue research related to 4D models, focusing on improving 4D tools and the value of 4D models in design and construction. Below is a list of research projects performed by graduate students under Martin Fischer's guidance and with support from the CIFE community and industry companies. The links lead to a more detailed description of these projects.
Last Updated Thursday, 12-Oct-2006 20:01:24 PDT.
Current Projects
Network Analysis of Project Teams to Understand and Enhance Diffusion of New
Technologies (Fischer,M. and Hartmann,T. 2006/10/01-2007/09/30)
Scheduling with 3D Model-Based Quantities (Fischer,M., Seppanen,O., and
Khandzode,A. 2006/10/01-2007/09/30)
Improving & Verifying Building Performance (Fischer,M. and Maile T. 2006/10/01-
2007/09/30)
Current methods and software tools that validate building performance during the commissioning or operations phase lack an integration of design intentions and a detailed concept of comparison of predicted and observed metrics. As a result most building systems do not operate efficiently, which leads to higher energy consumption and thermal comfort problems. This research project aims to develop a detailed methodology to automatically compare predicted and observed metrics so that the building performance can be verified and improved by more reliably detecting deficiencies in energy consumption and thermal comfort. The methodology will be developed based on current research and performance validation software tools by applying findings from case studies. The resulting advanced performance validation can reduce operating cost of buildings.
An Experiment to Combine POP, Narratives, and decision Dashboard Modeling for Better
Process Communication and Integration (Fischer,M., Haymaker,J., Kam,C., and
Toledo,M. 2005/10/1-2006/9/30)
See details on web site
How is VDC Implemented Globally - Contrasting Case Studies on the Implementation and
Benefits of 3D and 4D CAD in the U.S, Europe and China. (Levitt,R., Taylor,J., Fischer,M.,
and Gao,J. 2005/10/1-2006/9/30)
See details on web site
Organizing to Exploit Integrated Information Technologies: Exploring Firm Networks in the
U.S., Scandinavia & Japan (Levitt,R., Taylor,J., Fischer,M., and Gao,J. 2005/10/1-
2006/9/30)
Completed Projects
Completed: Screenshot Title and Author
October, 2000 Product Model 4D-Construction Pilot
Kam, Calvin
September, 2000Feature-Based Construction Cost Estimating
Staub, Sheryl
August, 2000Time-Space Conflict Analysis
Akinci, Burcu
We acknowledge the support of the National Science Foundation for some of the research presented here through awards 9309655, 9420398, 9513461, 9625228, 9726748, and 0075672. We also thank CIFE and its member companies and our many other industrial sponsors for their support of our work. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.