Abstract:
One embodiment of the present invention sets forth a technique for providing an end user with a spatially-aware projector combined with a spatially-aware digital pen for use in a design environment. Paper documents are augmented to allow a user to access additional information and computational tools through projected interfaces. Virtual ink may be managed in single and multi-user environments to enhance collaboration and data management. The spatially-aware projector pen provides end-users with dynamic visual feedback and improved interaction capabilities.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 61/310,657, filed on Mar. 4, 2010, which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the invention relate generally to computer software and, more specifically, to a method and system for bimanual interactions on digital paper using a digital pen and a spatially-aware mobile projector. 
         [0004]    2. Description of the Related Art 
         [0005]    The field of augmented reality has demonstrated the interesting properties which arise from augmenting physical artifacts with virtual imagery. In particular, there are many benefits in overlaying virtual information in situ of physical environments when a digital system is aware of its location. This idea has been extended with different display and tracking technologies to not only visualize, but also to manipulate virtual imagery in the context of a physical environment. Paper has been one of the most popular mediums to virtually augment due to its unique physical properties such as ubiquity, mobility, and scalability. 
         [0006]    Recently, virtual interactions on paper gained further interest due to the introduction of emerging digital pen technologies such as Anoto®. An Anoto®-based digital pen can capture and interpret, via a camera embedded therein, what users write onto surfaces. When combined with visual feedback, the pen can serve as a proxy to access virtual information associated with the physical paper. The virtual information can then be updated on paper and the next iteration begins. Depending on the properties of the visual feedback, different virtual interactions on paper are possible. One example is AutoDesk&#39;s® PenLight, described in U.S. patent application Ser. No. 12/537,013, entitled “A Spatially-Aware Projection Pen,” which simulates a mobile projector mounted on a digital pen and allows a dynamic visual overlay to be displayed on top of a surface. This increases the “functionality” of the paper, allowing a user to interact with virtual content such as ink and auxiliary data. Though PenLight&#39;s integration of pen input and projector output into a single device improves the mobility of the device, it disadvantageously fixes the pen tip to a single point within the projected image. As a result, users cannot make annotations and overlay virtual content independent of one another. 
       SUMMARY OF THE INVENTION 
       [0007]    One embodiment of the present invention sets forth a spatially-aware projector system, comprising a first position tracking mechanism configured to provide position data related to a current position of the spatially-aware projector within a display surface, and a projection unit configured to display a projected image generated from design data retrieved from memory based on the position data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0009]      FIG. 1  illustrates a system configured to implement one or more aspects of the present invention. 
           [0010]      FIG. 2  illustrates a detailed view of a digital pen according to one embodiment of the present invention. 
           [0011]      FIGS. 3A-3B  illustrates a detailed view of a spatially-aware projector according to one embodiment of the present invention. 
           [0012]      FIG. 4  illustrates an independent input/output technique according to one embodiment of the present invention. 
           [0013]      FIG. 5  illustrates a displaced input technique according to one embodiment of the present invention. 
           [0014]      FIG. 6  illustrates different virtual layers, according to one embodiment of the present invention. 
           [0015]      FIG. 7  illustrates a user interface that is projected onto display surface according to one embodiment of the present invention. 
           [0016]      FIGS. 8A-8B  illustrate a dominant hand menu selection performed via a radial menu that is included in a projected image according to one embodiment of the present invention. 
           [0017]      FIG. 9  illustrates a display surface that includes a floorplan that is overlaid with a projected image that displays virtual content according to one embodiment of the present invention. 
           [0018]      FIG. 10  illustrates a display surface that includes a floorplan that is overlaid with a projected image that hints at virtual content according to one embodiment of the present invention. 
           [0019]      FIG. 11  illustrates a display surface that is overlaid with a projected image that includes a color palette according to one embodiment of the present invention. 
           [0020]      FIG. 12  illustrates a display surface that is overlaid with a projected image that includes a stencil according to an embodiment of the present invention. 
           [0021]      FIG. 13  illustrates generating a video walk-through of an environment based on strokes generated by a user via a digital pen according to one embodiment of the present invention. 
           [0022]      FIG. 14  illustrates an in-place copy/paste technique according to one or more embodiments of the invention. 
           [0023]      FIG. 15  illustrates a displaced copy/paste technique according to one or more embodiments of the invention. 
           [0024]      FIG. 16  illustrates a flow diagram of method steps for performing a copy and paste function according to one embodiment of the invention. 
           [0025]      FIG. 17  illustrates a flow diagram of method steps for displaying overlay data for a computation according to one embodiment of the invention 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention. 
         [0027]      FIG. 1  illustrates a system  100  configured to implement one or more aspects of the present invention. The system  100  includes, without limitation, a central processing unit (CPU)  130 , a system memory  110 , a graphics processing unit (GPU)  115 , a device/memory bridge  105 , a network interface  145 , a digital pen  135 , and a spatially-aware projector  132 . The spatially-aware projector  132  is configured to be grasped by a non-dominant human hand while the digital pen  135  is configured to be grasped by a dominant human hand. The CPU  130  communicates with the system memory  110  via the device/memory bridge  105 , which may be, e.g., a Northbridge device or subsystem. System memory  110  is configured to store application programs, as well as data used by or generated by the CPU  130 . In particular, system memory  110  is configured to store design data  150 , such as computer-aided design drawings and information that is accessed by the application program  112 . System memory  110  is also configured to store image data  155  for display by the spatially-aware projector  132 . The image data  155  may be produced by the CPU  130  or a discrete GPU  115  based on design data  150  and/or data received via the spatially-aware projector  132  and the digital pen  135 . 
         [0028]    System memory  110  is coupled to the device/memory bridge  105  via a system memory bus  150 . The device/memory bridge  105  may be coupled to the GPU  115  that incorporates real-time image rendering means for rendering both three-dimensional (3D) and two-dimensional (2D) images. The CPU  130  or GPU  115  delivers pixel data to the spatially-aware projector  132 . In some embodiments, the integrated circuit implementing the CPU  130  may incorporate additional functional blocks, such as the device/memory bridge  105  and GPU  115 . 
         [0029]    The device/memory bridge  105  is also coupled to the network interface  144 , the digital pen  135 , and the spatially-aware projector  132 . The network interface  144  provides network connectivity to other computers in local or remote locations using any suitable technology, preferably a wireless technology. In particular, portions of design data  150  and image data  155  may be output to remote users via the network interface  144 . Similarly, data received from a remote user via the network interface  144  may be displayed and/or stored as design data  150  or image data  155 . 
         [0030]    Other components (not explicitly shown), including USB or other port connections, CD drives, DVD drives, film recording devices, and the like, may also be connected via network interface  145 . Communication paths interconnecting the various components in  FIG. 1  may be implemented using any suitable protocols, such as PCI (Peripheral Component Interconnect), PCI Express (PCI-E), AGP (Accelerated Graphics Port), HyperTransport, Quick Path Interconnect, or any other bus or point-to-point communication protocol(s), and connections between different devices may use different protocols as is known in the art. 
         [0031]    In one embodiment, system memory  110  is configured to store a graphics modeling or authoring application program  112  that is configured to access the design data  150  to provide image data  155  for display via spatially-aware projector  132  and use information acquired by the digital pen  135  and the spatially-aware projector  132  to display a user-interface or image data. 
         [0032]      FIG. 2  illustrates a detailed view of the digital pen  135  according to one embodiment of the present invention. As shown, the digital pen  135  includes a force sensor  202 , which indicates when the tip of the digital pen  135  is in contact with a display surface  208  and may be used to record pen strokes. An ink reservoir may be configured to deposit physical ink on the display surface when the tip of the digital pen  135  is in contact with a surface. 
         [0033]    A camera  204  is also included in the digital pen  135  and is positioned to enable 2D tracking using patterns printed on the display surface  208 . In one example, dot-pattern technology is used to provide the 2D tracking, where a unique dot pattern  212  is identified by camera  204  while scanning area  210 . The camera  204  may also be used to enable 3D optical tracking using traceable patterns to retrieve camera calibration parameters to determine 3D location and orientation. The patterns may also represent a hierarchical encoding pattern which allows the camera to cover a wide range of distances from the display surface  208 . Additional patterns may be printed on the display surface  208  in infrared ink to be less distracting to the user. 
         [0034]    In other embodiments, the digital pen  135  may include alternative tracking mechanisms to the camera  204 . For example, any type of proximity sensor, e.g., electromagnetic sensors may be included in the display surface  208  to detect a location of digital pen  135 . This configuration would advantageously enable the spatially aware projector  132  to be lifted a substantial distance from the display surface  208  while maintaining overall functionality and providing a larger projected image onto the display surface  208 . 
         [0035]    An input mechanism  206  is further included in digital pen  135  and may be implemented using a button that is configured to be activated and/or deactivated by a user, as described in further detail herein. 
         [0036]      FIGS. 3A-3B  illustrate a detailed view of the spatially-aware projector  132  according to one embodiment of the present invention. In order for the spatially-aware projector  132  to display the design data  150  and/or image data  155  as a visual overlay in the context of a paper document, the application program  112  needs to be aware of the spatial location of the spatially-aware projector  132  and the digital pen  135  relative to the display surface  208 . Capturing the location of the spatially-aware projector  132  and/or the spatially-aware pen  135  on the display surface  208  allows the spatially-aware projector  132  to display virtual information which is relevant to the existing physical content on the paper. The virtual information may be read from design data  150  or information previously captured by digital pen  135  from pen strokes stored as image data  155 . The digital pen  135  increases the user&#39;s ability to work with functionality that requires visual feedback, such as viewing the results of computations, and overlaying contextual information onto the digital paper  208  via spatially-aware projector  132 . 
         [0037]    In one embodiment, the spatially-aware projector  132  includes a handle  302 , a scroll wheel  304 , a digital pen  135   1 , a digital pen  135   2 , a micro-projector  306 , a small mirror  308 , a swivel handle  310 , and a large mirror  312 . The handle  302  may be grasped by a hand of the user to navigate the spatially-aware projector  132  across the display surface  208 . The scroll wheel  304  may be implemented using a scroll wheel of a mouse, and is used to, e.g., cause elements included within a projected image  314  to be scaled up or down. The projected image is dynamically updated to display virtual layers, as described in further detail below in conjunction with  FIG. 6 . Input received via digital pens  135   1  and  135   2  provides both a position and angle of the projector with respect to the display surface  208 . In other embodiments, alternative tracking mechanisms may be included within the spatially-aware projector  132 , such as the proximity sensors described above in conjunction with  FIG. 2 . Projected image  314  is displayed via micro-projector  306 , small mirror  308  and large mirror  312 . 
         [0038]    The angle of large mirror  312  is adjustable via the swivel handle  310  to increase or decrease the size of the projected image  314 . In this way, a user of system  100  is advantageously able to focus his or her work across a small or large portion of display surface  208 , as illustrated in  FIG. 3B . Note that the position of micro-projector  306  and small mirror  308  are not fixed and may also be adjusted, either alone or in combination, to influence projected image  314 . 
         [0039]    In addition, if a laser-based pico projector is used, the scanning pattern produced by the pico projector may be modified to reduce artifacts that are often visible when the large mirror  312  is angled to increase the size of the projected image  314 . For example, the spatially-aware projector  132  may include a mechanical controller, that, when adjusted, changes the spread between each raster line that is produced by the laser-based pico projector. This may be accomplished, for example, by modulating X and Y axis-based oscillating mirrors that relay the laser beam to different x,y coordinates of the large mirror  312 . Moreover, the oscillating frequency of these can be modified on demand using acousto-optic modulators. As a result, the artifacts may either be reduced or eliminated entirely. 
         [0040]      FIG. 4  illustrates an independent input/output technique  400  according to one embodiment of the present invention. As shown, the spatially-aware projector  132  produces a projected image  402  on display surface  208 . The location and orientation of the spatially-aware projector  132  and the digital pen  135  with respect to display surface  208  is carefully considered, since they affect the overall operation of the system in several ways. Digital pen  135   3  provides a direct link between input, e.g., pen strokes, illustrated as virtual input  404 , and output, e.g., projected image  402 . Importantly, decoupling the digital pen  135  and spatially-aware projector  132  allows for independent input and output. For example, the projected image  402  can be stationary while the digital pen  135  is used. In other words, the digital pen  135  and the spatially-aware projector  132  can be operated simultaneously and independently from one another. Additionally, multiple users may share the same display surface  208  and collaborate by each providing input via additional spatially-aware digital pens  135   4-X . Remote users may also provide input and see the same projected image  402  on a remote display surface  208 . 
         [0041]      FIG. 5  illustrates a displaced input technique  500  according to one embodiment of the present invention. Another property resulting from decoupling the digital pen  135  and spatially-aware projector  132  is the capability to provide input via the digital pen  135  outside of the projected image  402 . For example, the user can write a “search” keyword via displaced virtual input  502  outside the projected image  402  on a separate display surface  208   2  and the search results can be included in the projected image  402 . Furthermore, users can interact with the projected image  402  on a separate display surface  208  to interact with virtual display elements located thereon. 
         [0042]      FIG. 6  illustrates different virtual layers, according to one embodiment of the present invention. The display layers include the physical display layer  260  and the virtual display layer(s)  265 . The virtual display layers  265  may include multiple separate virtual layers that are overlaid. Each virtual layer may include one or more of user printout database layers  270 , user database layer  275 , and/or viewport layer  280 . The physical display layer  260  is the layer which physically exists on the display surface  208  and may include a variety of different elements. Examples of elements include printed content, such as a diagram or two-dimensional building layout, ink created by the user, and user interface elements, such as menus and icons, preprinted on the physical display layer  260 . 
         [0043]    Above the physical display layer  260  are one or more virtual display layers  265  that may be combined to produce the projected image  402 . A variety of display elements may be projected onto the virtual display layers  265 . Printout database layer  270  contains auxiliary data that is displayed in the context of the printed content. For example, if a map is printed on a piece of paper, the printout database consists of vector images and text labels of either printed content or electronically stored content. Display elements within the printout database layer are locked on-surface and aligned with the underlying printout. Printout database layer  270  may be useful for displaying aspects of the design data  150  that are not included in the physical display layer  260 . For example, when multivalent documents that consist of multiple abstract layers of distinct—but closely coupled content—are used, then only some of the abstract layers may be included in physical layer  260 . Multivalent documents are especially prevalent in the application domain of architecture and three-dimensional modeling, e.g., different floor plans, section views, and additional metadata to describe materials and processes. 
         [0044]    User database layer  275  includes any new virtual display element, which is added by the user. For example, when a user creates ink (annotation or sketching) on top of the paper, the stroke is inserted into this layer. The contents of this layer are also locked on-surface. The most basic functionality of the digital pen  135  is creating virtual and/or physical ink. The digital pen  135  enables users to create and manage virtual ink that users can then make use of in different functions, such as tracing and drawing virtual guides. In some embodiments, the input mechanism  206  is used to change from a pen tip with physical ink to a pen tip using virtual ink that is displayed within the projected image  402 . When virtual ink is enabled, all pen strokes are added to the virtual ink display layer  265 , in the location of the display surface in which they are created. The user database layer  275  may be stored in image data  155  or design data  150 . Hence, the annotations are added to only the virtual display layer  265 . This allows a user to annotate a blueprint without altering the original document. 
         [0045]    Users can trace over both physical and virtual content within projected image  402  to produce trace data that is captured and stored in image data  155 . The trace data may be applied to different special locations within the display surface  208 . Users may also load existing virtual templates to trace out with physical ink input. The resolution and size of the virtual content being traced may be adjusted via, e.g., the scroll wheel  304 , or by displaying a virtual menu in projected image  402  that may be navigated using a digital pen  135 . 
         [0046]    Instead of tracing, virtual guides may be created to aid in generating a physical sketch. Such grids and guides are widely used in image editing applications, but unavailable when working on physical paper. To create a geometric guide, the user can select the line circle, rectangle, or grid menu display element, as described in further detail below in conjunction with  FIG. 7 . Instead of entering points that define the geometry, the user may draw a similar shape and the digital pen  135  will approximate the selected shape. For example, the user can draw a circle using the digital pen  135  on the display surface  208 , and the location of digital pen  135  relative to the display surface  208  determines the center point and the radius. In grid mode, users may draw a rectangle that serves as the unit rectangle shape of the grid. Once the digital pen  135  is lifted, the entire virtual layer is covered with a self replicating grid layout. 
         [0047]    Viewport layer  280  contains global user-interface controls that enable a user to change the settings of the printout database layer  270  and the user database layer  275 . To keep these elements available at all times, viewport layer  280  is not bound to a specific location of the display surface  208  but instead locked in-hand. Note that the printout database layer  270  and user database layer  275  are page-dependent while the viewport layer is application-dependent. Hence, when the digital pen  135  and/or spatially-aware projector  132  are placed on a different page, the spatially-aware projector  132  displays different content, but the same user-interface controls. An exemplary user-interface is described in detail below in conjunction with  FIG. 7 . 
         [0048]      FIG. 7  illustrates a user interface  700  that is projected onto display surface  208  according to one embodiment of the present invention. As shown, user interface  700  is included in projected image  402  and allows for display, combination, and/or manipulation of the virtual display layers  265  displayed within the interaction region  706 . To access and control system features, the spatially-aware projector  132  displays the user interface  700 . To manipulate virtual content displayed within projected image  402 , contextual marking menus can be displayed within the viewport layer  280 , thereby providing the user with a diverse set of command execution options. The user interface  700  includes one or more database layer toolbar  702  icons  704  in the top border of the projected image  402 , and one or more icons  710  in the toolbar  708  included in the bottom border of the projected image  402 . The database layer toolbar  702  allows users to toggle the visibility of the printout database layer  270  and the user database layer  275 . Additionally, touching and holding the digital pen  135  to the display surface  208  causes a marking menu (not shown) to be displayed within interaction region  706  and enables selection of various menu display elements, as described in further detail below in conjunction with  FIGS. 8A-8B . For example, if working with a college campus map, layers such as “library”, “dining”, and “overview” could be menu display elements in the marking menu that could be activated or deactivated. Icons  710  included in toolbar  708  may be used to, e.g., modify colors of virtualized data, copy and paste virtualized data, perform search functions, enable camera view, and/or operate drafting tools, as described in further detail below. 
         [0049]      FIG. 8A  illustrates a dominant hand menu selection  800  performed via a radial menu  802  that is included in projected image  402  according to one embodiment of the present invention. The radial menu  802  may be implemented using hierarchy to access various functions of the system. The radial distribution of menu display elements in regions  802 ,  804 ,  806 , and  808  that are separated by region boundaries, e.g., region boundary  810 , simplifies use of the radial menu  802  since users only need to remember what direction to move towards. Here, a virtual cursor is bound to the tip of the digital pen  135 , and is used to control the selection of regions  802 ,  804 ,  806  and  808 . Users can access the radial menu  802 , e.g., by activating the input mechanism  206  on digital pen  135  to cause the top level of the radial menu  802  to be displayed in virtual display layers  265 . In contrast, conventional digital pen menu systems rely on menus that are preprinted on the display surface. 
         [0050]    The user can select a menu display element in two ways, as illustrated in  FIGS. 8A-8B . The first method involves a dominant hand menu selection technique  800 , where the user can use a traditional method of moving the digital pen  135  in the direction of the menu display element, as illustrated in  FIG. 8A . Alternatively, the user can use a non-dominant hand menu selection technique  850 , illustrated in  FIG. 8B . Here, user instead moves the spatially-aware projector  132  with the non-dominant hand (i.e., the hand that is not holding the digital pen  135 ) in the opposite direction of the menu display element while keeping the digital pen  135  fixed and pressed against the display surface  208 , thereby repositioning the menu display element under the pen tip. Advantageously, the non-dominant hand menu selection technique  850  allows users to perform menu display element selections without leaving a physical ink trail on the display surface  208 . 
         [0051]      FIG. 9  illustrates a display surface  208  that includes a floorplan that is overlaid with a projected image  900  that displays virtual content according to one embodiment of the present invention. The projected image  900  includes electrical components  902 . Note that the electrical components  902  are only visible within the projected image  900 . In other embodiments, the projected image  900  may include additional components or additional layers, e.g., heating, ventilation, mechanical, lighting, and the like. 
         [0052]    The overlaid content or the original physical content may be copied to another location on display surface  208  to be overlaid. The user enters a copying mode using the radial menu  802  and indicates an area using the digital pen  135  to specify a contextual parameter of the projected image  900  or the image printed on the display surface  208 . The user then enters a pasting mode using the radial menu  802 , and the copied content is displayed using the locked in-hand metaphor and copied when the user engages the input mechanism  206 . 
         [0053]      FIG. 10  illustrates a display surface  208  that includes a floorplan that is overlaid with a projected image  1000  that hints at virtual content according to one embodiment of the present invention. The virtual display layers  265  enable computations to be performed and the results displayed in the contexts of the user&#39;s workspace. The user may perform a measurement query by selecting a particular element to be measured using the spatially-aware projector  132  and/or digital pen  135  and engaging a dimension tool to overlay the measurement information. Using the radial menu  802 , the user can choose to measure a distance, path length, area, or volume. Alternatively, the user may create a line or bounding box using the digital pen  135 , where the measurements of the line or bounding box are displayed in the projected image  1000 . The measurement computation is displayed by the spatially-aware projector  132  within the projected image  1000 . 
         [0054]    A search command may allow users to search for elements that exist within the virtual display layers  265 . The user can perform the query in two ways. First, they can choose from a list of query elements, e.g., sprinklers, outlets, and the like, in the search menu provided by the radial menu  802  as described above. Alternately, the user can directly select an instance of an element on display surface  208  or within projected image  1000  using the digital pen  135 . For example, the user may perform a query to search for electrical outlets. In response, the outlets  1002 —which are outside of the projected image  1000 —are hinted to by halos  1004 , where each halo corresponds to an outlet that is nearby, but not within, the projected image  1000 . Halos  1004  may guide the user to additional instances of the element that was searched, allowing the user to find elements of interest faster. The user can also adjust the swivel handle  310  to increase the size of the projected image  1000  to navigate toward or to display the elements corresponding to one or more of the halos  1004 . Alternatively, the user can relocate the spatially-aware projector  132  perform the navigation. 
         [0055]      FIG. 11  illustrates a display surface  208  that is overlaid with a projected image  1100  that includes a color palette  1104  according to one embodiment of the present invention. Here, each section of the color palette  1104  includes a unique border color. To change the property of a virtual display element, e.g., an electrical component  1102 , the user first aligns the color palette  1104  on top of a display element included in printout database layer  270 . Then, the user can tap on the electrical component  1102  through the color palette  1104  to change the color of the electrical component  1102 . To simplify the manipulation, the color palette  1104  can be resized via scroll wheel  304 . The color palette  1104  can also be relocated within projected image  1100  via a handle attached to the color palette  1104 . 
         [0056]      FIG. 12  illustrates a display surface  208  that is overlaid with a projected image  1200  that includes a stencil  1202  according to an embodiment of the present invention. Here, the stencil  1202  is representative of any drafting tools that are used to guide a user when he or she is drawing across the display surface  208  using a digital pen  135 . Like the color palette  1104 , the stencil  1202  is resizable via the scroll wheel  304 . In addition to the virtual ink that can be used to trace drawings, drafting and measurement palettes can also be used as virtual “stencils” that help users guide their physical pen strokes (i.e., ink strokes). In one embodiment, these stencils include rectangle and circle shape tools, a protractor, and French curves. 
         [0057]      FIG. 13  illustrates generating a video walk-through of an environment based on strokes generated by a user via a digital pen  135  according to one embodiment of the present invention. The user may draw a path, such as walkthrough path  1300 , on the display surface  208  with the digital pen  135 . Frames of the two-dimensional walk-through represented as pixel data, as viewed from a viewpoint moving along the walkthrough path  1300 , are generated by the CPU  160  or the GPU  115  and stored in the image data  155  for playback as a walk-through animation. The playback may be projected onto the display surface  208  by the spatially-aware projector  132  and/or played back on alternative output devices, e.g., a liquid crystal display (LCD) monitor. As the frames are being displayed via spatially-aware projector  132 , the position  1302  indicates the position along the walkthrough path  1300  that corresponds to the current frame that is displayed. Additionally, the walkthrough path  1300  and position  1302  may be used as a slide bar and slide bar position interface element, respectively, for the user to navigate a corresponding frame that he or she desires to view. 
         [0058]      FIG. 14  illustrates an in-place copy/paste technique  1400  according to one or more embodiments of the invention. As described above in conjunction with  FIG. 4 , independent input and output allows users to select different parts of the viewport layer  280  and to easily select menu display elements. When the copy and paste feature is activated, the user can use the viewport layer  280  as a clipboard to copy a display element, e.g., an electrical component  902 , from one location to another within a display surface  208  that includes electrical component  902 , or in another display surface  208 . There are two steps involved when copying an display element from one location of a display surface  208  to another location. The user first copies the display element from the database layer  275  to the viewport layer  280 . Then, users paste the display element into the desired location of the user database layer  275  by using in-place copy/paste technique  1400  or displaced copy/paste technique  1500  described in further detail below in conjunction with  FIG. 15 . 
         [0059]    When performing an in-place copy/paste technique  1400 , the object selection occurs within the viewport layer  280 , and the in-place paste can occur from the database layer  275  to the viewport layer  280  thereby, which creates a hyperlink between the virtual display elements. The spatially-aware projector  132  is then repositioned to a desired paste location, whereupon the user can paste the copied display element from the viewport layer  280  to the database layer  275 . 
         [0060]      FIG. 15  illustrates a displaced copy/paste technique  1500  according to one or more embodiments of the invention. As illustrated, when a display element that lies outside of the projected image  402  is selected, the displaced copy/paste technique  1500  is used. When the display element is selected and copied with the digital pen  135 , its virtual representation is copied to the viewport layer  280 , and an active hyperlink is created as described above. This active hyperlink enables the user to select the display element again using the dominant hand to access a contextual marking menu for the copied display element, where the contextual marking menu is displayed in the viewport layer  280 . Selecting a paste submenu display element will paste the display element to the user database layer  275 . Display elements can be copied from one layer to another because different contextual marking menus are shown depending on the underlying information layer. For example, if display elements are located in the user database layer  275 , then a menu containing “copy” pops up so that the printout database layer  270  can be used as source of copy. Similarly, if a display element is located inside the viewport layer  280 , a menu containing “paste” pops up. When the user transfers display elements to the viewport layer  280  or to the user database layer  275 , different types of representations can be selected. The user may copy its raw digital representation using a “shape” submenu. If the user wants to copy an iconic representation that displays meta-data such as the direction to its original location within the display surface  208 , the user can select an “icon” submenu. For error management, users can correct and undo their copy and paste operation using different techniques. In one example, users can select a “delete” submenu on display elements in user database and viewport layers. In another example, the user can reposition display elements within the viewport layer using the “move” submenu. Note that users can either move the digital pen  135 , or move the spatially-aware projector  132  to change the relative location of the display element in the viewport coordinate system. 
         [0061]    In-place and displaced manipulations are also available in the search functions described herein. When the search feature is activated, the user can execute a search by either writing or clicking the display element to be searched inside the projection area (in-place) or outside the projection area (displaced). When the user writes the display element to be searched, the pen strokes are gathered and translated into text that the CPU  130  is able to interpret. For example, if the user writes “wireless” on a separate display surface  208 , and the projector is placed on top of a display surface  208  that corresponds to a college campus, then buildings with wireless support will be highlighted. If the projector is placed on top of a document, a text bounding box of the search results will be highlighted. If the result is inside the viewport, then the result is simply highlighted with an outline. If the result is outside the viewport, the halo technique may be used as described above in conjunction with  FIG. 10 . There are a variety of ways to initiate a search. For example, users can write a keyword, or lasso a phrase already written as part of an annotation, or lasso printed text. The search considers not only the printout database layer  275  but also display elements on the user database layer  275  that the user may have added while during previous interactions with a corresponding display surface  208 . 
         [0062]      FIG. 16  illustrates a flow diagram of method steps  1600  for performing a copy and paste function according to one embodiment of the invention. The method begins with step  1602  where the user selects the overlay data to be displayed in the projected image  402 . The data may be selected using the projected radial menu  802 . At step  1604 , the application program  112  updates the overlay data in the projected image  402  via the spatially-aware projector  132 . At step  1606 , the user activates a copy mode. At step  1608 , the user selects a region or an element within the display surface  208  or the projected image  402 . At step  1610 , the application program  112  stores in memory within image data  155  an image of the copied region or element. At step  1612  the user selects a paste position within the display surface  208  using the spatially-aware projector  132 . At step  1614 , the application program  112  updates the overlay image to include the copied region or element. At step  1618  the updated overlay image is displayed via the spatially-aware projector  132 , whereupon the user is able to complete the paste function as described above. 
         [0063]      FIG. 17  illustrates a flow diagram of method steps  1700  for displaying overlay data for a computation according to one embodiment of the invention. The method begins at step  1702  where the user selects a region or element on display surface  208  or within projected image  402  using the digital pen  135 . At step  1704 , the application program  112  obtains the data corresponding to the selected region or element. At step  1706 , the application program  112  performs one or more computations specified by the user. At step  1708 , the application program  112  updates the overlay image to include the computation result. At step  1710 , the updated overlay image is displayed via the spatially-aware projector  132 . 
         [0064]    The printed content that is visible on the display surface is only one abstract view of a larger electronic file that is stored in the design data  150  within system memory  110 . For example, when a two-dimensional floor plan is printed on the display surface  208 , the digital pen  135  may directly access a highly detailed three-dimensional model that is stored as the design data  150  or image  155  or generated by the CPU  130  or GPU  115  using the design data  150 . A view of the three-dimensional model may be displayed within the projected image  402  that is output by the spatially-aware projector  132 . 
         [0065]    In sum, the spatially-aware projector and digital pen enable the use of virtual ink in addition to conventional physical ink. The virtual ink may be used to capture commands, annotate an existing design, and communicate with a remote user. The virtual ink may be displayed as a projected image on a display surface by the spatially-aware projector. Auxiliary design information and rendered images may also be displayed in the projected image. The spatially-aware feature of the projector and digital pen allows for gestures to be interpreted differently based on the position of the spatially-aware projector and digital pen in a given space. 
         [0066]    As a result, paper is no longer just a static source of data, but it is also used as the display surface and a dynamic workspace. Virtual ink benefits the user by providing visual feedback without permanently modifying the physical display surface. The spatially-aware projector and digital pen enable a user to interact with the design more efficiently and intuitively. 
         [0067]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. For example, aspects of the present invention may be implemented in hardware or software or in a combination of hardware and software. One embodiment of the invention may be implemented as a program product for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein) and can be contained on a variety of computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the present invention, are embodiments of the present invention. 
         [0068]    In view of the foregoing, the scope of the present invention is determined by the claims that follow.