1. INTRODUCTION
Over the past decade, CAD software for construction has gone from simple 2D drafting programs to complex 3D solid modeling systems that support structural analysis, logical product models, project management information systems, collaborative environments, and task scheduling. The hardware on which those programs run has progressed from mainframes to desktop computer and laptops. The size of computer storage and memory has gone from megabytes to gigabytes. Communication between client-server applications has advanced from dialup modems to always on broadband and wireless networks.
Mobile handheld computers and personal digital assistant (PDA) such as Pocket PC [1] and Palm [2] devices are now gaining acceptance as useful tools at a construction site [3]. Software applications previously confined to the engineerâ„¢s office, are now available on the construction site. They provide a means to have access to project information that is stored locally on the PDA or accessed from a server through a wireless Internet connection. The information can also flow in the opposite direction where the PDA is used to collect data from the construction site and is communicated back to desktop applications for subsequent processing.
Although 3D solid modeling is becoming more popular, there are very few applications for doing 3D visualization on PDAs. A common format used for displaying 3D models on desktop computers is the Virtual Reality Modeling Language (VRML) [4,5], which is a scene description language for representing 3D interactive models on the web. VRML models are displayed in freely available VRML plugins [6, 7, 8, 9] for Netscape or Internet Explorer. A VRML browser has also been developed for the Pocket PC [10]. Most CAD programs can export their models in VRML format; however, the VRML representation of a CAD model is not well suited for viewing on a Pocket PC because of its memory and computational limitations. The VRML generated from CAD programs usually does not take advantage of any of the useful features in VRML to make the file sizes smaller and more efficient.
2. HARDWARE
The most common type of handheld computers are PDAs that run either the Palm or Windows CE operating system. PDAs typically have a screen resolution of 240 x 320 pixels. This low 2 screen resolution limits the type of 2D or 3D information that can be effectively displayed. Traditional methods of displaying data on a normal sized computer monitor are often not appropriate for PDAs and new visualization paradigms need to be developed. Devices running the Palm OS usually have 8 MB of memory while newer Pocket PCs running Windows CE typically have 64 MB of memory. Depending on the operating system, the memory is used to store the operating system, applications, and files and provide memory to run programs. PDAs normally do not have a fixed hard disk. Currently the processors in PDAs are not very powerful or suited to dealing with large amounts of data that might be needed for 3D CAD applications. The first 2D graphics accelerators for Pocket PCs are only beginning to be available.
The user interacts with the PDA using a stylus to pick menu items or to write on the screen. Some PDAs have a small joystick-like device to aid in navigation. Detachable keyboards can also be used to enter information. Files and applications are usually transferred to and from a PDA by synchronizing with a host computer. Information can be transferred directly between PDAs or other computers by beaming it through an infrared port.
Most PDAs have expansion slots for compact flash memory, wireless Internet access, and other CF or PC expansion cards such as global positioning system receivers or barcode scanners. Some PDAs have built-in wireless access. There are even PC expansion cards that incorporate a 1 GB miniature hard drive. With this amount of storage on a handheld device, an enormous quantity of information can be brought to the construction site. One of the primary limiting factors for displaying 3D data on a PDA is the amount of built-in memory. Adding memory or a hard drive through an expansion slot only increases the amount of space available for storing programs and files. The memory available to run programs is restricted to whatever is built-in to the PDA. For example, in a Pocket PC running Windows CE with 64 MB of memory, by default, half of the memory is allocated to storing programs and files and the other half to running programs. The memory allocation between storing and running programs can be adjusted to provide more or less of the built-in memory to each function.
There are also several PDAs that run the Linux operating system. Larger pen-based tablet computers run the Windows XP operating system. One manufacturer has even developed a pocket-sized computer that runs Windows XP with a 10 GB hard disk and 256 MB of memory .
2.1 Common Characteristics of Palm and Pocket PC
Palm and Pocket PC devices are similar in size and make up. Their form factors lend themselves to easily being carried in ones pocket. They come with a stylus to enter data and help navigate through the various functions of the device. They have cradles that charge their batteries and allow them exchange data, or synchronize with a desktop computer. They also have infrared abilities to allow them to send and receive information from other devices.
Much like desktop computers, PDAs have hardware specifications:
¢ Processor type
¢ Clock speed
¢ Quantity of storage space
¢ Types of peripheral interfaces available
The market trend has shown that most manufactures are catering to both low and high end device consumers. The lower end devices generally have smaller price tags, slower processors, less storage space, and less expansion abilities. In contrast, the higher end devices offer faster processors, increased onboard storage capacity, additional built-in functionality, and may be better equipped for future expansion. A higher price generally accompanies these as well.
Some of the peripherals available for PDAs include:
¢ Fold-up and thumb keyboards for speedy data entry “ these can be very useful during meetings and classes.
¢ Compact Flash (CF) cards for additional memory storage, modems, hard drives, external video display cards “ can be hooked to projectors for presentation graphics, cameras, Ethernet cards, and wireless Ethernet cards.
¢ Secure Digital (SD) cards for additional memory storage, wireless Ethernet cards, external video projector interfaces, and others. Contrary to the size of images in figures 5 and 6, SD has a much smaller form factor that of CF.
Palm and Pocket PC devices have different approaches for offering some of their common functionalities. Both offer Personal Information Manager (PIM) type functions in that they can keep date books, contacts, To Do lists, and offer ways to jot down notes. Above and beyond that they can share information with desktop computers.
Palm devices interface and synchronize with desktop computers using a program called HotSync. This is installed on the desktop machine along with an application called Palm Desktop. Palm Desktop allows access to much of the information stored on the PDA. Pocket PC devices utilize Microsoft ActiveSync to synchronize with a desktop PC. This program is installed on the desktop PC and allows synchronization of folders, files, and Internet favorites so that they may be kept on both the PC and the PDA.
As GroupWise is the WVU standard for faculty and staff to use for calendar and e-mail functionality, it is often desirable to have that information available on PDAs. Neither device offers native support to synchronize with the GroupWise. This can be achieved through a 3rd party product called IntelliSync .Once installed on the desktop PC, it can also allow for synchronization with the GroupWise calendar and partial functionality with e-mail. At this time, we have found other methods such as IMAP4 configuration for e-mail may be more useful.
Both HotSync and Active sync allow for the backing up of data that exists on the PDA. This is an important feature to utilize, as there are few things than loosing ones data. Something as trivial as a battery becoming fully discharged can cause some models to totally lose their information. Regular backups to a desktop machine or to an add-on memory card can help minimize the effects of temporary data loss and ease the recovery process.
2.2 Data entry methods
Palm devices utilize a handwriting data entry system called Graffiti. Learning and executing these predefined strokes is an effective way to take short notes or enter small amounts of data. The data is entered on an area below the portion of the screen that information is displayed on. This rectangular shaped writing area has small arrows drawn just to the right of center on the top and bottom lines that depict an imaginary column where by letters are entered on the left side and Pocket PC devices have six onboard modes for information entry. Two of them are similar to those available on the Palm platform, block entry and soft keyboard modes. In block entry mode, the bottom portion of the PPC display screen depicts a rectangle that resembles and emulates the physically permanent graffiti entry area of Palm devices. If you are familiar with Palmâ„¢s graffiti and are considering making a switch, you will be right at home with block entry mode. Both Palm and PPC devices also offer an on screen keyboard where characters are selected by tapping keys with the stylus numbers on the right using graffiti.
Both types of devices can use external fold-up keyboards, and also snap on thumb boards. For rapid data entry these are hard to beat. If you are considering purchasing a new PDA and find this type of accessory desirable, check availability and compatibility of keyboards for your specific model.
2.3 Palm Device Specifies
Palm devices feature an easy to learn interface. They can be synchronized with both Macintosh and PC platform computers. They come with Palm Desktop software, which is a personal information manager in and of it. The built in four major functional applications of the Palm devices include: Contacts, Date book, Notepad, and To Do List. For those using GroupWise, Intellisync software will allow Date book and Contacts to synchronize with these functions of the unit. On some models an Inbox is included for email functionality.
As Palm has licensed its operating system out to numerous vendors, there are variations on functionality from one model to another outside of the ones that Palm markets itself. Some models offer color screens, some have integrated thumb boards for typing data in, some are integrated into cellular phones, and some even come with built in cameras. Manufacturers such as Handspring, Sony, Kyocera, and Samsung are among those offering Palm compatible devices.
Some popular accessories for Palm devices include snap on modems that allow dialing into an Internet service provider over traditional phone lines. An Internet connection this way can be used to send and receive mail, and do some minimal web browsing through a number of programs. There are also some wireless add on services available for some Palm brand PDAs, but unfortunately the Morgantown area currently has little to offer in that regard. At this time, the only cellular phone carrier in our area that has some data abilities for smart phones (integrated devices that function as both a cell phone and a PDA) is Sprint PCS.
The new high end Palm Tungston line comes with a software package that allows interaction with Microsoft Office documents. A wealth of 3rd party software exists for things such as reading Adobe Acrobat PDF files as well. Palm devices have square display screens. The resolutions are generally either 160 x 160 pixels or 320 x 320 pixels. The higher number offers better the quality of display. Depending on the device, it will either have a Motorola Dragonball or Texas Instruments OMAP processor in it. The Texas Instruments processor is used in the PalmOS version 5 devices, and Motorola has various versions of the Dragonball chip for other PalmOS based units.
2.4 Pocket PC Specifics
Pocket PC devices offer tight integration with the Windows desktop operating system and Microsoft Office. They give a familiar interface and the ability to open and work with Excel spreadsheets, Word documents, and graphics among other things. Windows Media Player is included which allows for playing audio and video media content. They also have the ability to send and receive e-mail and attachments when configured to connect to supported servers.
Under current standards, Pocket PCs generally have 32 or 64 megabytes of RAM onboard. There are two popular PPC processor types, Xscale and Strong ARM. Xscale is the current technology. It is backward compatible with applications written to run on the older Strong ARM processors.
Internet connectivity to these devices is available in a number of ways. It can be achieved through physically being in a cradle attached to an Internet connected PC, a wired Ethernet adapter card, a wireless Ethernet card, a modem, and slowly via an infrared page link to other Internet enabled devices. Once properly configured and connected, these devices can access web sites through Pocket Internet Explorer and e-mail through the inbox application. There is wealth of other programs written for these devices to enhance capabilities as well.
Pocket PC models have 6 onboard methods for creation of new information:
1. Block Entry “ Predefined strokes with the stylus are used in a manner similar to Palm graffiti.
2. Soft Keyboard “ An image of a keyboard is displayed and keys are tapped with the stylus.
3. Letter Recognizer “ Gives another way to write using the stylus and a special rectangular area of the screen similar to that of block entry mode. In this instance, one writes traditional printed letters and they are interpreted on the Screen.
4. Transcriber “ Normal handwriting is done on any part of the screen and translated into printed characters from script.
5. Drawing mode “ While entering information into a note, drawing mode can be selected to draw with the stylus.
Examples of Pocket PC devices are shown
3. SOFTWARE
Several CAD and construction related software applications are commercially available for PDAs. In general, the more complex and graphics oriented applications run on PocketPCs with the Windows CE operating system. Applications that run on Palm devices are usually text oriented such as punch list, project management, or scheduling software. Research into collaborative dynamic project management has shown how PDAs and even web-enabled cellphones can be used as wireless display devices for traditional desktop construction management software.
A number of 2D graphics applications that display traditional CAD drawings in DWG, DXF, or DGN formats are available for PDAs. Some of the programs can display the drawings directly, while others require that the drawing be converted to a proprietary format that is optimized for the software. Other applications provide the means to markup existing or create new CAD drawings. Certainly the low screen resolution and small screen size are limiting factors for the utility of working with CAD drawings on a PDA. Version control of CAD drawings between a PDA and desktop computer is also of concern. Simple file synchronization may be inadequate when format conversions are taking place on one platform but not the other. The development of 3D visualization programs is only in its infancy. At least two commercial products are available for developing and delivering 3D content and applications for PDAs and other mobile devices. However, these applications are geared towards 3D games and not to 3D visualization for CAD. Preliminary research at IBM led to the development of a 3D viewer that could display a subset of VRML on a Pocket PC.
Pocket Cortona [10] is an inexpensive VRML viewer for Pocket PCs that supports most of the VRML specification including application specific nodes. VRML models that are generated by CAD programs can be displayed in Pocket Cortona without modifications. Pocket Cortona can run in a standalone mode or as a plugin to a web browser. In the standalone mode, the VRML file to be displayed is stored locally on the Pocket PC. Pocket PCs with a wireless Internet connection, web browser, and Pocket Cortona can access VRML models through a web page in the same way they are accessed on a desktop computer.
4. VRML
4.1 What is VRML and where did it come from?
VRML pronounced either "V-R-M-L" or "vermil", is an acronym for Virtual Reality Modeling Language. As its name suggests, VRML is analogous to HTML, or Hypertext Markup Language (in fact, VRML was originally coined as Virtual Reality Markup Language). Like HTML, VRML describes exactly how text, graphics and links all fit together to form a page on the World Wide Web. Where HTML defines the layout of a two-dimensional page, however, VRML is a markup language that can be used to create three-dimensional (3-D) spaces, often referred to as "virtual worlds."
VRML is an ISO standard for describing 3D geometric objects and their behaviors. Information in a VRML model is arranged in a scene graph that defines the parent-child relationship between VRML nodes. Some common VRML nodes describe 3D shapes, the appearance of the shapes, and geometric transforms that can be applied to the shapes. The shapes include primitives such as boxes, spheres, cones, cylinders, extrusions, and general sets of points and polygons known as Indexed Face Sets. Transforms that can be applied to the primitives include translation, rotation, and scale.
VRML first took shape in the spring of 1994, at the First International Conference on the World Wide Web in Geneva. Although a number of individuals played and continue to play a big part in VRML's development, the three most prominent shapers of the language include Mark Pesce (Labyrinth Group), who conceptualized VRML, Anthony Parisi (Intervista Software), and Gavin Bell (Silicon Graphics), who wrote the specification for the VRML 1.0 standard.
More specifically, VRML is referred to as a "scene description language," because it tells a VRML viewer, or browser, how to construct a 3-D environment. VRML differs from HTML in that it gives the browser instructions about where objects go and what color they are and then basically lets the browser "connect the dots." HTML, on the other hand, simply pieces together text and a number of different, pre-existing image files to form a 2-D page.
Typically the VRML models exported by CAD programs use Indexed Face Sets and geometric transforms to represent all of the geometry in a model. While this provides an accurate visual representation of the geometry, it does not take advantage of several features of VRML to reduce the file size and make the processing of the VRML model much more efficient. The VRML prototype mechanism allows for the creation of application-specific geometric objects similar to the built-in primitives such as boxes, spheres, cones, and cylinders. Research at NIST has developed a mapping between the CIMsteel Integration Standard (CIS2) and VRML. CIS2 is a logical product model for describing steel structures and has been adopted by the American Institute of Steel Construction as their standard for electronic data interchange. VRML prototypes have been developed that correspond to CIS2 entities such as parts (beams, columns, braces, clip angles, plates), bolts, holes, welds, and locations.
Another important feature of VRML, which is usually not implemented in the VRML model exported by a CAD program, is the ability to define one geometric object and create many instances of it. In a typical steel structure there are many identical parts, each with their own location. In the VRML model only one of each type of part needs to be modeled. The rest of the VRML model is built from instances of the defined parts. This is much more efficient than modeling all of the geometry explicitly.
VRML models using the CIS2 related VRML prototypes represent a steel structure much more efficiently, effectively, and intelligently than the VRML models exported from a CAD program. Therefore much larger models can be displayed in a VRML browser on a handheld computer. With this capability, 3D visualizations of CAD models of steel structures can be viewed in the field at a construction site.
4.2 VRML worlds and Web sites
VRML files can be quite large, so a 2-3 minute wait (with a 28.8 Kbps modem) is not uncommon. More specifically, we need a special VRML viewer, or browser. These browsers are available as stand-alone programs from many different vendors on the Web. Alternatively, if we are using Netscape Navigator or Microsoft's Internet Explorer as our Web browser, we can use a VRML plug-in or add-in that operates within these popular browsers. We can download most of these products at no cost from the vendors Web sites. VRML viewing is also very taxing on your computer's resources, so a fast computer (e.g., 486/66 minimum) with more RAM (8 MB minimum) and a fast video card (16-bit or better) will greatly improve your virtual experience.
Both stand-alone and plug-in versions of VRML players should come with instructions for setting up the browser, although some vendors make this information available on their sites. Once we download the browser and configure it, we should be able to visit any VRML-enriched site on the Web. Note, however, that some vendors have added proprietary non-standard extensions to the standard VRML language. This may make some VRML worlds designed for specific browsers incompatible with the viewer we are using.
To aid us in our search for the best VRML browser, Web Developer has compiled this listing of some of the most popular viewers and plug-ins:
Table 4.2.1 VRML Browsers/Plug-ins
Of course, the number of VRML viewers and plug-ins continues to grow at a rapid pace. For a regularly updated and fairly comprehensive list of VRML browsers, see The VRML Repository's Software/Browser section. Netscape also maintains a collection of most of the VRML plug-ins available for Navigator. Finally, version 3.0 of both Netscape's Navigator and Microsoft's Internet Explorer are equipped with built-in VRML support. The Web's VRML worlds are many and varied, ranging from entertainment sites to real world applications. What better way to start your VRML tour than with a test drive? If your interested, might as well go in style on Cybertown's BMW Freeway (you'll need Macromedia's Shockwave as well). While your visiting Cybertown, step into The NetGate, which will transport you to random VRML sites across the 'Net. Continue your tour by visiting virtual cities such as Amsterdam, San Francisco and Tuscany.
Of course, VRML isn't just about flying around in cool virtual worlds. It is also being applied in the arts and sciences to create some fun and useful learning tools. To get a taste of how VRML is being used in the arts, for instance, check out the Net in Arcadia VRML Wing. Or see how biomedicine is utilizing VRML in this 3-D model of the human heart. The list goes on and on!
Finally, for one of the most complete collections of VRML worlds on the Web, be sure to visit Weblynx's Ultimate Virtual Worlds Library. Netscape's Cool Worlds, Aereal's BOOM: 1000 VRML Worlds and Protein Man's Top Ten VRML Sites are also great places to jump into our virtual Web experience.
Exactly how we can navigate VRML worlds is dependent upon which VRML browser we are using. However, most of the available viewers use related methods to move around virtual scenes, including navigation toolbars, mouse input, keyboard strokes, or a combination of all of these. Since Netscape's Live3D plug-in is one of the most popular VRML viewers, let's take a quick look at its means of navigation as an example. Again, our particular browser should either come with specific instructions for navigation or provide online help on the company's Web site.
When we enter a VRML world with Netscape's Live3D viewer, Navigator's background turns black and a navigation toolbar appears at the bottom left of the browsing window. Unless the scene has a very small file size, the toolbar will appear long before the world is downloaded completely. Wait until the status bar at the bottom of the browser reads "Document: Done", then the scene is ready for you to navigate. We now have several options to move around: you can use your mouse to move the cursor over the VRML scene, click and hold left mouse button and go (note: we'll move as if we were using a joystick: up=forward, down=backward, etc.). Or we can use the direction arrows on our keyboard to accomplish the same thing (note: use the arrows while holding down the control or shift key for added movement options). Finally, we can use a joystick with some VRML viewers, although it will have to be calibrated to work correctly.
Once we've learned the basics of navigating VRML scenes, we can now select various options to customize your experience. Using the navigation toolbar, we can simply click on the different options to change how we move (Walk, Spin, Look or Slide) and turn our "headlights" (Lamp) on or off. For even more options, however, move the cursor over the scene and click the right mouse button. This activates a pop-up menu, from which we can fine tune our navigation (Fly instead of walking!), change the look and amount of detail in the site (in the Lights and Detail menus) and even save our settings once they are customized (in the Options menu).
4.3 Authoring tools available to create VRML worlds
As with VRML browsers, the list of VRML authoring tools is expanding rapidly as VRML's popularity contiues to grow. If we just want to "experiment" with the creation of VRML scenes, there are a couple of Web-interactive sites that allow us o build simple 3-D objects remotely. At Aereal's Instant VRML Home World, for instance, we can input text and have it generated in 3-D. Our creation is then stored on Aereal's server, and we can page link to it from from our home page/Web site.
For those ready to get fully immersed in VRML world creation, we've constructed a list of some of the best VRML authoring environments on the Web. Most VRML editors are WYSIWYG tools that generate code automatically, so we don't necessarily have to learn VRML to create 3-D worlds.
Table 4.3.1 VRML Authoring Tools
4.4 Basic components of the VRML language
All VRML file must begin with a simple file header string, which in the case of VRML 1.0 is:
#VRML V1.0 ascii
This identifies the file to the VRML browser, so it knows to interpret, or parse, the contents of the file. The basic components, or objects, of VRML are called Nodes. There are three types of nodes: Shape nodes, which describe an object's geometry; Property nodes, which modify the way an object is drawn; and Grouping nodes, which group objects together as a single object. Different nodes are grouped hierarchically into Scene Graphs, which compose VRML worlds, or scenes.
Shape nodes: VRML supports four pre-defined, or primitive shape nodes: Cube, Cone, Cylinder and Sphere.
Property nodes: one of the most important property nodes is the Material node, which determines an object's color and appearance. Colors are defined using Red/Green/Blue (RGB) values expressed as fractions of 1.
Grouping nodes: the most important grouping node is the Separator node, which allows the other nodes within it to be treated as a single object.
Using these few components, then, an example of a red sphere would look like this:
#VRML V1.0 ascii
Separator {
Separator {
Material {
emissiveColor 1 0 0
}
Cone {}
}
}
View the example in 3-D.
Fig 4.4.1 3D view of cone
Of course, this is a very simple example of VRML code. The VRML specification contains 36 different nodes, each with its own set of arguments. For a more complete look at the VRML 1.0 specification, see The VRML Repository's Language Specification section.
VRML files are treated as basic MIME (Multipurpose Internet Mail Extension) types. More than likely, the problem is that our server, or our Internet Service Provider's (ISP) server, has not been configured to handle the VRML MIME type. We should configure our server for the MIME type x-world/x-vrml and filename extension .wrl, or ask our ISP to do the same.
4.5 How do we incorporate VRML in our HTML files?
There are two basic ways to add our VRML scenes to a Web page. The first is to create a simple hyperlink using the VRML file's URL, such as:
<A HREF="http://webdeveloperwdworld.wrl">Web Developer's VRML World</A>.
This option best serves external VRML browsers (as opposed to plug-ins) and "full-immersion" VRML worlds.
If we want to incorporate smaller scale VRML scenes as images on a Web page, however, one of the best methods is to use the <EMBED> tag. As with the <IMAGE> tag, we can control the height, width and alignment of the scene, so that a common embed tag line would be:
<EMBED SRC="http://webdeveloperwdworld.wrl" HEIGHT=100 WIDTH=100 ALIGN=RIGHT>.
One of the most common methods used to compress VRML files is "gzip" compression, developed by the Free Software Foundation's Project Gnu. The compression utility is freely downloadable from the gzip home page.
4.6 What is "Moving Worlds"? How is it different from VRML 1.0?
Moving Worlds is the name of a Silicon Graphics' proposal that was chosen as the specification for VRML 2.0. The final draft of the VRML 2.0 spec was released in August, 1996. The difference between 1.0 and Moving Worlds is analogous to the development of Web pages: 1.0 enables the creation of static virtual scenes, whereas 2.0 effectively adds multimedia and animation capabilities to VRML. With 2.0, VRML authors can now add music or sound files in the background, animate objects, drop in realistic backgrounds and terrains, and even attach behaviors to elements in a scene.
5. EXAMPLES
6. CONCLUSION
These examples show how 3D visualizations of steel structures can be displayed on a PocketPC. The VRML models are generated directly from CIS2 files and use VRML prototypes and other features to make the VRML files smaller and more efficient to process. Although there are limitations to the size of a VRML model that can be effectively displayed on a PocketPC, the inevitable improvements in processing power and graphics accelerators for handheld computers will provide an improvement for 3D visualization in the future. Within several years, it should be practical to make 3D visualization on PDAs a commonplace tool at construction sites.
REFERENCES
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[4] Ames A., Nadeau D., Moreland J., VRML 2.0 Sourcebook (2nd edition), John Wiley & Sons, Inc., 1997.
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