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Home , Architectural model, Design tool, Immersive design

A Tablet Based Immersive Architectural Tool

Ross Tredinnick Lee Anderson Brian Ries Victoria Interrante University of Minnesota D’Nardo Colucci, Ph.D The Elumenati, llc, Minneapolis, MN

Abstract

In this paper we describe a SketchUp VR system in which we create a hybrid two-dimensional / three-dimensional immersive architectural design system. This system combines a tablet PC, an optically tracked room, a display wall, a SpaceTraveler motion controller, and stereographic eyewear to allow immersive and walkthrough using a version of SketchUp that has been enhanced with Ruby plug-ins. The tablet PC provides a ”sketchpad” type of user interface for SketchUp, while the tracked and display wall enable the simultaneously to design at full (or any other) scale in an immersive (VR) environment.

Introduction Both traditional and paradigms have their advantages and Traditional applications disadvantages that will be discussed prior provide a screen-based paradigm, to describing our hybrid system. whereby an exists A typical modeling application includes within a window on a flat display screen. viewing tools that facilitate designing More recently, advancements in virtual at a wide range of scales. To place new environment technology have triggered the geometry in the environment at a distant emergence of a new paradigm, known as location from the current viewpoint, a immersive architectural design (Anderson camera pan tool quickly shifts the center 2003). Immersive architectural design of design to the necessary location. On programs utilize hardware, the other hand, can modify tiny such as a HMD, to place the designer’s details of an intricate model by zooming in viewpoint inside of the model. Geometry and focusing the center of design on small creation and manipulation takes place by areas of a model. way of a three-dimensional input device.

328 Despite this practical functionality changes requiring precise movements for changing views, some downfalls exist may be difficult with a three-dimensional for the desktop . The input device. Finally, a three-dimensional designer using a modeling application user interface must be considered to is performing a highly integrative act, avoid awkwardly re-introducing a two- attempting to create an environment dimensional user interface into a supposed with a strong physical three-dimensional three-dimensional environment. presence. Designing with the inherently In this paper, we introduce SketchUp two-dimensional desktop interface, limits VR, which attempts to combine the better the design process. Modeling applications features of the screen-based and virtual- effectively limit the viewing angle and based design paradigms. The system joins provide only limited screen resolution, several pieces of virtual environment which tends to objectify the design space, hardware together with a tablet PC to leading to a focus on external form rather create a hybrid system for design. We build than inhabitable space. The design may be the software system upon the popular also be negatively affected by the display SketchUp modeling application. SketchUp screen, with and its strong vertical and contains a built-in Ruby application horizontal edges and fixed aspect ratio. programming interface, which we use The emergence of virtual reality to extend SketchUp to be an immersive technology introduced a new possibility design application. The user employs for architectural design. Immersive SketchUp on a tablet PC to create , architectural design places the designer while simultaneously being immersed within the environment of the model, in virtual environment. All changes to giving a realistic sense of scale and the SketchUp model are simultaneously presence. This design method has the changed in the virtual environment. potential for overcoming several of the negative aspects of the desktop paradigm. Related Work For example, a dynamically changing viewpoint exists, often with stereo viewing, Advancements of virtual environment which leads to a greater sensation of technology triggered a change in the way presence of the inhabitable space being we can interact with a software program. designed. Although immersive modeling Virtual environment researchers adhere to may seem more beneficial than traditional this important idea everyday by designing desktop based programs, problems systems that allow three-dimensional emerge here as well. First of all, navigation immersive interaction. Architectural design becomes more of an issue. Placing new has become a very popular area in terms geometry in the model at a distant of immersive technologies and many location from the current focus requires immersive modeling systems have been an intuitive, easy form of navigation. Also, designed and tested (Butterworth 1992), the modification of small details may (Donath and Regenbrecht 1996), (Mine require additional viewing tools to zoom 1997a), (Mine et al. 1997b), (Forsberg in on locations, which may feel unintuitive et al. 1998), (Donath et al. 1999), (Hill within a head mounted display. Small detail et al. 1999), (Regenbrecht et al. 2000),

Tredinnick, Anderson, Ries, Interrante, Colucci A Tablet Based Immersive Architectural 329 (Dave 2001), (Anderson et al. 2003). In SketchUp. Unlike their system and also like addition, much research has gone into previous differences, our work renders understanding how digital technology through a projection-based display rather advancements can benefit the conceptual than a head mounted display. design stage in (Campbell and Wells 1994), (Bowman 1996), (Bridges The Hardware System and Charitos 1997), (Bowman et al. 1998), (Kukimoto et al. 1999), (Lau and Maher Our hybrid system combines several 2000), (Schnable et al. 2001), (de Vries et al. pieces of virtual environment technology 2001), (Schnable 2002). to create an immersive design area. There has been a fair amount of The total system consists of an optical literature about combining the two- tracking system, a curved display wall, dimensional design metaphor into the three PCs, one tablet PC, a 3D Connexion three-dimensional virtual environment. SpaceTraveler, and Crystal Eyes 3D stereo The majority of previous work done in glasses, two stereo emitters. I will discuss this area combines a tracked clipboard how each feature fits into the system or drawing pad with a tracked pen stylus. below. The system is shown in action in The 3Draw system introduced such a user figure 1. interface (Sachs et al. 1991). Their system allowed three-dimensional sketching Tracking System of splines to model objects. Unlike our system, their work was not immersive, The room that holds our project and interaction occurred through a plain contains a Hi-Ball 3000 wide area optical desktop monitor. Since then, various tracker (Welsh et al. 1999). We mount the systems have combined a tracked ceiling of our room with several infrared clipboard and pen within a head mounted light emitting diode strips that allow a display environment (Angus and Sowizral HiBall sensor to calculate position and 1995), (Bowman et al. 1998), (Schmalsteig orientation. The total amount of tracked et al. 1999), (Chen et al. 2004). Our space roughly measures thirty feet by work differs from this work in two main twenty four feet. The system provides respects: first of all, our system runs on a projection-based display rather than a head mounted or workbench display; and secondly, interaction occurs through an actual tablet PC running windows and SketchUp rather than a tracked clipboard. Another piece of significant work that has some commonalities with our system is the worlds in miniature system (Stoakley et al. 1995). Like their system, our tablet PC contains a de-coupled camera viewpoint from the display wall and Figure 1. A student works on an apartment model manipulation of objects may occur through using the system.

ACADIA 2006: Synthetic Landscapes Digital Exchange 330 Digital Dissemination: Dissemination and Representation updates to a Hi-Ball sensor at a rate of AMD Athlon 64 X2 Dual Core 3800+ PCs 500-800 Hz. We mount a Hi-Ball sensor on with 1 gigabyte of RAM compliment the top of a basic white construction helmet three projectors. Each PC holds a NVidia that the designer wears. The tracking Quadro FX 4500 graphics card with 512 system provides position and orientation MB of video memory. The graphics cards information for our software system and are supplemented with NVidia gSync dynamically updates the layout of the cards to enable proper stereo viewing. virtual scene based on current position Figure three shows the display wall. The and view direction toward the screen. The display wall provides the immersive three- HiBall sensor transmits information over dimensional stereoscopic display of the wire to a CIB box that knows the layout architectural design system. of the system on the ceiling and converts the data to a point that represents Tablet PC position and a quaternion that represents orientation. To transfer tracking data We run the SketchUp program between the CIB and our software system, and our accompanying software on a we interface with the VRPN software Toshiba Portégé tablet PC. The tablet PC library (Taylor II et al, 2001). Figure two contains an Intel Pentium M 2.00 gigahertz shows a picture containing a portion of processor with 1 gigabyte of RAM. The the tracking system. user interfaces with the tablet PC by directly applying its accompanying pen Display Wall stylus to the screen. The use of a tablet PC provides mobility within the immersive The room contains a curved display environment. wall, back projected by three Christie Mirage 4000 stereoscopic projectors. The Spacetraveler wall measures eight feet tall by twenty four feet wide and has a total display area of We optionally accompany the system thirty feet by eight feet. The wall viewing with a 3D Connexion SpaceTraveler. angle measures roughly 128 degrees. Three The SpaceTraveler interfaces with the

Figure 2. A picture of the diode strips for the optical HiBall tracking system mounted on the ceiling in our lab. Figure 3. The curved immersive display wall.

Tredinnick, Anderson, Ries, Interrante, Colucci A Tablet Based Immersive Architectural Design Tool 331 display wall to provide three-dimensional Ruby API gives any designer access to navigation within the design environment. most aspects of the SketchUp program The SpaceTraveler connects to the tablet through a collection of Ruby classes. PC. Updates of position and orientation Documentation for these classes are sent to the display wall through the accompanies the SketchUp program. Ruby networking of our software system. commands may be issued by way of a simple Ruby input console in SketchUp. Stereo Glasses For example, a user can modify the default front color of a face by typing the We use CrystalEyes three-dimensional following command into the Ruby console: stereo shutter glasses and place two Sketchup.active_model.rendering_options stereo emitters within range of the display [“FaceFrontColor”] = Color.new (255, wall. Combining this with stereo rendering 0, 0). In addition to changing rendering on the display wall gives a significant three- details, the Ruby API contains classes for dimensional presence while modeling using building unique tools, creating fly-through the tablet PC. The user is still able to view animations, and adding new user interface the tablet PC while wearing the stereo buttons and menus for custom purposes. glasses because the screen on the tablet One critical factor in the SketchUp PC contains a plastic layer that re-polarizes Ruby API that allows the extension of the light. Without this plastic layer, the SketchUp to a virtual environment is its tablet PC screen would disappear while built-in animation class. The animation class wearing the stereo shutter glasses. acts as a template to allow a background loop to run within the SketchUp design Software System environment. A user may run an animation within the SketchUp environment by We have built a unique software creating a Ruby class that contains system on top of the commercially the necessary nextFrame method of available SketchUp design program. The the Ruby API. The nextFrame method software system contains three basic would then modify the viewpoint of the pieces: the SketchUp Ruby interface, the camera over some period of time. In our networking software written using basic implementation, we ignore modifying the windows sockets in C++, and a C++ viewpoint and instead make use of the OpenGL-based rendering engine of the animation loop in a different manner. SketchUp environment for the display wall. A second important feature of the We describe the three portions of the SketchUp Ruby API intrinsic to our software system in this section. system is the attribute dictionary class. An attribute dictionary is a collection SketchUp Ruby API of arbitrary features that attach to a SketchUp entity. An entity is the term Ruby is an interpreted scripting SketchUp adopts for a piece of geometry, language developed by Yukihiro Matsumoto such as a face or edge. An attribute for quick and easy object oriented dictionary acts as a basic hash table, programming tasks. The SketchUp therefore allowing both fast assignment

ACADIA 2006: Synthetic Landscapes Digital Exchange 332 Digital Dissemination: Dissemination and Representation and retrieval of extra information about a The Network piece of geometry. Attribute dictionaries greatly extend the functionality of the In order to transfer SketchUp data to SketchUp design program. For example, the PCs controlling the display wall, we suppose extra information concerning wrote our own networking software to cost and manufacturing date need to transfer the entity information from the be retained for a group of building tablet PC to the three PCs controlling components. Each extra piece of the wall projectors. We implement a information could be read into an attribute basic client server model to achieve dictionary and displayed in a report proper transmission of data. In our detailing that information in the current model, the tablet PC acts as a server SketchUp model. and communicates with a total of four We have written a Ruby script that clients, itself, and the three PCs running incorporates these two features of the the wall. The tablet PC must communicate SketchUp Ruby API. The script acts as with itself in order to obtain SketchUp an updating loop for controlling when information. At the time of this paper, and what information is sent across our although the Ruby scripting language has a network. The script runs a background useful networking class, the class is unable loop in SketchUp and maintains various to load within the SketchUp Ruby API attributes about the current geometry context. To work around this, we adopted within a SketchUp model. On each frame, a built-in SKSocket module provided the script loops through all current entities with the SketchUp software. The module of the model, checking to see whether the provides very basic socket communication, entity has been sent across our network. only allowing communication through a If we have not sent the entity across single socket at a time. This eliminated the network yet, we transmit a message our proposed option of communicating containing geometrical and material data from the Ruby API directly to the about the entity. If we had previously three wall PCs. We therefore have the sent the entity across the network, our SketchUp Ruby script send data to a C++ program checks to see if either an entity’s networking program that simultaneously visual attribute or physical location has executes on the tablet PC, so that the changed within the model. If so, we re-send information can be queued and forwarded a message across the network containing to the three PCs controlling the display updated information about the entity. wall. Upon running the program, and before To transfer entity information we have beginning our updating loop, we write out developed a simple, yet effective, message a basic text file containing initial model system that allows variable length packets data to a network folder so that the three of data to be sent across the network. PCs controlling the wall can parse the file We create a method to pack data into a and prepare to render the initial scene. character string for each entity type in This pre-process creates an initial scene SketchUp. The string contains first, a single on the wall faster than if we were to send character signifying the type of entity, all data over the network. followed by material and physical location

Tredinnick, Anderson, Ries, Interrante, Colucci A Tablet Based Immersive Architectural Design Tool 333 data. On each frame we store all current models that designers can insert into updates in an array and, after checking all their model from a built-in component current entities, create a packet containing browser. All entities within the SketchUp the total length of the updates followed program possess a unique identifier called by a string containing all of the new an entityID whose value may be accessed information. The tablet PC forwards the through the Ruby API. The entityID is packet to the three PCs that parse the included in messages we send across data and update the rendering context. the network and provides a convenient key for a hash table that we maintain to Rendering display objects. After a wall PC retrieves a SketchUp message from the network, The final portion of our software we store its data and generate a single system retrieves SketchUp data from the display list, if the entity is a face or edge. network and re-displays it on the curved If the entity is a component instance, we display wall. The SketchUp design program generate a hierarchical display list. The contains a sketchy, non-photorealistic hierarchy resembles a tree whereby the display style to emphasize the program as root represents the outer most parent a conceptual stage design tool. We have component, each inner node represents mimicked their rendering style as closely a nested component, and each leaf of the as possible to maintain equivalent visual tree is a collection of faces and edges. information between the tablet PC and the Each inner node compiles its own display wall. We implement the system in C++ via list whose call is then compiled into the the OpenGL graphics library for rendering display list of the root component. The and via the Win32 API for windowing. The display list structure of our rendering rendering consists of two sided lighting, system allows for fast rendering speeds, texturing, basic triangular polygons, and and smooth interaction between lines for highlighting edges of objects, SketchUp entities on the tablet PC and which add to the non-photorealistic feel corresponding data on the display wall. of the program. We have the ability to To accurately render the SketchUp render our scenes with stereo viewing for data on the curved wall surface, we increased three-dimensional realism and borrowed previously used techniques presence. for rendering to curved display surfaces; We implement a hierarchical display however, unlike this earlier work, our list system in order to render the various techniques do not calibrate the screen entities of the SketchUp program. with cameras (van Baar et al 2003). The SketchUp entity system contains Instead, we generate a mesh representing three basic primitives: faces, edges, and the screen using our optical tracking component instances. A component system. We mount a HiBall 3100 sensor instance is a group of edges, faces, onto a HiBall stylus and augment the and possibly other nested component stylus with a metal pointing rod. We click instances. Component instances are points on aligned grids displayed by the saved in separate files from the current three projectors to record points in SketchUp model. They serve as miniature tracker space. With the tracker space

ACADIA 2006: Synthetic Landscapes Digital Exchange 334 Digital Dissemination: Dissemination and Representation input points, we generate splines to SpaceTraveler quickly transforms the approximate the surface shape of the position and orientation of the viewpoint screen. We then projectively texture the on the display wall to navigate to a distant scene onto the approximated mesh using location. The viewpoint on the tablet graphics hardware. We render a seamless PC can be separately orbited, panned, image by using three different viewing zoomed or set to a specific location by frustums whose parameters depend on way of the various camera tools inherent the person’s currently tracked position to SketchUp. In this way, the tablet PC and view direction toward the screen. We viewpoint can zoom in and manipulate are working on improving the blending at small details on a SketchUp model, while the boundaries of the projected images. A users can critique the effects of the summary diagram of the whole system is changes on the whole object by looking shown below in figure four at the display wall. Executing minutely detailed changes in a regular immersive System Features environment poses more challenges due to the need to manipulate overly sensitive By combining a tablet PC based display three-dimensional input devices. An with an immersive display wall, we have example of the de-coupled viewpoints is formed a virtual environment system with shown in figures five and six. several unique features. The following sections will discuss each of these features Scale in turn. The SketchUp program also includes Retaining SketchUp Tools tools for accurately measuring distances and angles through a tape measure and By building a system on top of a a protractor tool. Additionally, SketchUp popular, commercially available software contains an inferencing system that product, we retain the convenient design allows easy creation of specifically sized tools inherent to the SketchUp program geometric primitives in relation to other current primitives in the model. The De-coupled Viewing system snaps tools to specific points in space such as the midpoint of an edge The system de-couples the camera or a line perpendicular to the corner of viewpoint on the tablet PC from the a box. These two features easily allow viewpoint on the immersive display wall. the creation of designs to detailed scales. This feature allows users to design on With a desktop-based program, such the tablet PC from a traditional desktop drawings still do not achieve a true sense based viewpoint, while at the same time of scale, since we view the model through to become immersed in their creation a window on a small screen display. With through a viewpoint realistically positioned our tracked display system, we have the in the model. Designers can freely walk ability to accurately create geometrical about a limited space of the environment objects of specific sizes on the tablet PC by way of our tracking system. The and then view these objects at real scale

Tredinnick, Anderson, Ries, Interrante, Colucci A Tablet Based Immersive Architectural Design Tool 335 Figure 4: A summary diagram of the Ruby updating loop, the networking and the layout of our display wall. The Ruby script runs on our tablet PC and messages are sent to its C++ networking code. The tablet PC forwards the messages onto the display PCs.

Figure 5. A screenshot of a SketchUp apartment model. Figure 6: The model displayed on our wall from an interior viewpoint.

ACADIA 2006: Synthetic Landscapes Digital Exchange 336 Digital Dissemination: Dissemination and Representation on our wall display. This introduces an language, Ruby, with traditional C++ element whereby the designer can quickly based, networking software and OpenGL critique various portions of a model at life- rendering system. We utilize graphics size scale directly after modeling it on the hardware to projectively texture a tablet PC. SketchUp model onto the mesh acquired with our optical tracking system. Our Portability curved wall provides an immersive stereoscopic display environment. The As is, our system is not completely desktop portion of the system builds portable; however, it is possible that the upon a popular commercially available SketchUpVR system could be constructed CAD program and retains many of its on a different virtual environment valuable features. The tablet PC works well hardware setup. Since our program because it retains the pencil and paper- communicates with our tracking system based architectural design metaphor and via VRPN, a publicly available program for communicates over a local ethernet with obtaining tracking data over a variety of the display PCs. SketchUp’s ability to insert virtual reality tracking devices, the system a wide variety of component models could work with a multitude of trackers. could ease virtual environment creation The networking system could easily be for research or application purposes. The modified to communicate with a different ability to port the system to a different number of PCs. The part of our system virtual reality setup is not out of the that would potentially require the most question. modification is the rendering system. We have several possible additions The rendering system would have to be and utilizations for the system. We plan changed to adhere to a different display to obtain a user study of the system setup. Nonetheless, with the proper to determine its effectiveness when software, the SketchUpVR system could compared to other forms of three- be displayed on a four, five, or six-sided dimensional immersive design. We also plan CAVE or any form of curved or dome to incorporate the system for studying projection-based display (Cruz-Neira et al, the effects of scale on conceptual design 1993). in architecture. We also plan to compare the effectiveness of our hybrid system to Conclusions / Future Work desktop and immersive 3d design alone. We plan to explore the possibility of We have created a hybrid two- adding different rendering styles to our re- dimensional / three-dimensional tablet creation of the SketchUp model. Improving based design tool for immersive graphics to achieve photorealistic quality architectural design and walkthrough. or modifying the rendering for different The tool retains the advantages of non-photorealistic painterly styles may desktop based CAD programs, as well introduce different effects on the design as immersive architectural modeling process. Adding shadows to introduce an programs. The system combines a high extra depth cue is also on the horizon. We object-oriented interpreted scripting also plan to implement a lighting system by

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ACADIA 2006: Synthetic Landscapes Digital Exchange 340 Digital Dissemination: Dissemination and Representation Tredinnick, Anderson, Ries, Interrante, Colucci A Tablet Based Immersive Architectural Design Tool 341