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METHOD AND SYSTEM FOR DISPLAYING
STEREOSCOPIC DETAIL-IN-CONTEXT
PRESENTATIONS
This application is a continuation of U.S. patent applica- 5 tion Ser. No. 10/289,453, filed Nov. 7, 2002, now U.S. Pat. No. 7,088,364 the disclosure of which is incorporated herein by reference.
This application claims priority from Canadian Patent Application No. 2,361,341 filed Nov. 7, 2001, the disclosure 10 of which is incorporated herein by reference.
The invention relates to the field of computer graphics processing, and more specifically to a method and system for displaying stereoscopic detail-in-context presentations.
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BACKGROUND OF THE INVENTION
Display screens are the primary interface for displaying information from a computer. Display screens are limited in size, thus presenting a challenge to graphical user interface 20 design, particularly when large amounts of information are to be displayed. This problem is normally referred to as the "screen real estate problem".
Well-known solutions to this problem include panning, zooming, scrolling or combinations thereof. While these 25 solutions are suitable for a large number of visual display applications, these solutions become less effective where sections of the visual information are spatially related, such as maps, three-dimensional representations, newspapers and such like. In this type of information display, panning, zoom- 30 ing and/or scrolling is not as effective as much of the context of the panned, zoomed or scrolled display is hidden.
A recent solution to this problem is the application of "detail-in-context" presentation techniques. Detail-in-context is the magnification of a particular region of interest (the 35 "focal region" or "detail") in a data presentation while preserving visibility of the surrounding information (the "context"). This technique has applicability to the display of large surface area media, such as maps, on limited size computer screens including laptop computers, personal digital assis- 40 tants ("PDAs"), and cell phones.
In the detail-in-context discourse, differentiation is often made between the terms "representation" and "presentation". A representation is a formal system, or mapping, for specifying raw information or data that is stored in a computer or 45 data processing system. For example, a digital map of a city is a representation of raw data including street names and the relative geographic location of streets and utilities. Such a representation may be displayed visually on a computer screen or printed on paper. On the other hand, a presentation 50 is a spatial organization of a given representation that is appropriate for the task at hand. Thus, a presentation of a representation organizes such things as the point of view and the relative emphasis of different parts or regions of the representation. For example, a digital map of a city may be 55 presented with a region magnified to reveal street names.
In general, a detail-in-context presentation may be considered as a distorted view (or distortion) of a portion of the original representation where the distortion is the result of the application of a "lens" like distortion function to the original 60 representation. A detailed review of various detail-in-context presentation techniques such as Elastic Presentation Space may be found in a publication by Marianne S. T. Carpendale, entitled "A Framework for Elastic Presentation Space" (Carpendale, Marianne S. T, A Framework for Elastic Pre- 65 sentation Space (Burnaby, British Columbia: Simon. Fraser University, 1999)), and incorporated herein by reference.
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In general, detail-in-context data presentations are characterized by magnification of areas of an image where detail is desired, in combination with compression of a restricted range of areas of the remaining information (i.e. the context), the result typically giving the appearance of a lens having been applied to the display surface. Using the techniques described by Carpendale, points in a representation are displaced in three dimensions and a perspective projection is used to display the points on a two-dimensional presentation display.
In present detail-in-context presentation systems, when a lens is applied to a two-dimensional continuous surface representation, for example, the resulting presentation appears to be three-dimensional. In other words, the lens transformation appears to have stretched the continuous surface in a third dimension. In addition, shading the area transformed by the lens further reinforces the three-dimensional effect of the resulting presentation. Thus, in present systems, stretching and shading, two monocular perceptual cues, are used to provide an illusion of depth for detail-in-context presentations displayed on two-dimensional display screens.
One shortcoming of these detail-in-context presentation systems is that the monocular stretching and shading techniques do not generally yield effective three-dimensional effects for a range of presentations. This is especially so for presentations that include stereoscopically paired images or anaglyphs. For example, the ability to provide users with three-dimensional effects that are comfortable to view is of great value in extending the capabilities of detail-in-context presentations to applications involving essentially planar representations having data with relatively small depth differences. Such applications may include digital maps produced from stereoscopic satellite images.
A need therefore exists for the effective display of stereoscopic detail-in-context presentations in detail-in-context presentation systems. Consequently, it is an object of the present invention to obviate or mitigate at least some of the above mentioned disadvantages.
SUMMARY OF THE INVENTION
In general, the present invention provides for the effective presentation of stereoscopic detail-in-context presentations in detail-in-context presentation systems through the use of improved stereoscopic rendering techniques and an improved graphical user interface.
According to one aspect of this invention, there is provided a method for generating a stereoscopic presentation of a region-of-interest in a monoscopic information representation comprising the steps of: (a) selecting first and second viewpoints for the region-of-interest; (b) creating a lens surface having a predetermined lens surface shape for the regionof-interest, the lens surface having a plurality of polygonal surfaces constructed from a plurality of points sampled from the lens surface shape; (c) creating first and second transformed presentations by overlaying the representation on the lens surface andperspectivelyprojecting the lens surface with the overlaid representation onto a plane spaced from the first and second viewpoints, respectively; and, (d) displaying the first and second transformed presentations on a display screen to generate the stereoscopic presentation.
According to another aspect of the invention, there is provided a method for generating a stereoscopic presentation of a region-of-interest in a stereoscopic information representation, the stereoscopic information representation including first and second images, comprising the steps of: (a) selecting a viewpoint for the region-of-interest; (b) creating a lens
surface having a predetermined lens surface shape for the region-of-interest, the lens surface having a plurality of polygonal surfaces constructed from a plurality of points sampled from the lens surface shape; (c) creating first and second transformed presentations by overlaying the first and 5 second images on the lens surface and perspectively projecting the lens surface with the overlaid first and second images onto a plane spaced from the viewpoint, respectively; and, (d) displaying the first and second transformed presentations on a display screen to generate the stereoscopic presentation. 10
According to another aspect of the invention, there is provided a method for generating a stereoscopic presentation of a region-of-interest in a stereoscopic information representation, the stereoscopic information representation including first and second images, comprising the steps of: (a) selecting 15 first and second viewpoints for the region-of-interest; (b) creating a lens surface having a predetermined lens surface shape for the region-of-interest, the lens surface having a plurality of polygonal surfaces constructed from a plurality of points sampled from the lens surface shape; (c) creating first 20 and second transformed presentations by overlaying the first and second images on the lens surface and perspectively projecting the lens surface with the overlaid first and second images onto a plane spaced from the first and second viewpoints, respectively; and, (d) displaying the first and second 25 transformed presentations on a display screen to generate the stereoscopic presentation.
According to another aspect of the invention, there is provided a graphical user interface (GUI) for manipulating a stereoscopic presentation of a region-of-interest in an information representation displayed on a display screen of a computer display system, the computer display system including the display screen, a computer, and a pointing device for positioning a cursor on the display screen. The GUI includes: (a) a representation of a first slide bar, the first slide bar having a first active area, the first active area for adjusting a separation distance between first and second viewpoints for the region-of-interest by repositioning the first active area with the pointing device; (b) a representation of a second slide bar, the second slide bar having a second active area, the second active area for adjusting a height of a projection plane for generating the presentation above a basal plane by repositioning the second active area with the pointing device; and, (c) a representation of a third slide bar, the third slide bar having a third active area, the third active area for adjusting a height of GUI interface icons, including the first, second, and third slide bars, above the basal plane by repositioning the third active area with the pointing device.
According to another aspect of the invention, a stereo- 5Q scopic presentation can be used for converting a raster representation to a vector representation by inversion of the stereoscopic presentation.
According to another aspect of the invention, a stereoscopic presentation can be used for editing or annotating a 55 representation by inversion of the stereoscopic presentation.
Advantageously, the stereoscopic rendering method of the present invention may be applied to a wide variety of detailin-context presentations. In particular, the present invention improves the presentation of three-dimensional detail-in- 60 context effects in applications involving essentially planar representations having data with small depth differences (e.g. digital maps produced from stereoscopic satellite images). These stereoscopic rendering techniques of the present invention provide, for example, the effect or illusion that a lensed 65 area of a presentation is protruding out of the display screen toward a user. A further advantage of the present invention is
that through a graphical user interface, a user may quickly and easily adjust stereoscopic lens parameters for improved viewing comfort.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention may best be understood by referring to the following description and accompanying drawings. In the description and drawings, line numerals refer to like structures or processes. In the drawings:
FIG. 1 is a graphical representation of the geometry for constructing a three-dimensional (3D) perspective viewing frustum, relative to an x, y, z coordinate system, in accordance with known elastic presentation space graphics technology;
FIG. 2 is a graphical representation of the geometry of a presentation in accordance with known elastic presentation space graphics technology;
FIG. 3 is a block diagram illustrating an exemplary data processing system for implementing an embodiment of the invention;
FIG. 4 a partial screen capture illustrating a graphical user interface having lens control elements for user interaction with stereoscopic detail-in-context data presentations in accordance with an embodiment of the invention;
FIG. 5 is a graphical representation of the geometry for constructing stereoscopic perspective viewing frustums in accordance with an embodiment of the invention; and,
FIG. 6 is a flow chart illustrating a general method for a general method for generating a stereoscopic presentation of a region-of-interest in a monoscopic information representation in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it is understood that the invention may be practiced without these specific details. In other instances, well-known software, circuits, structures and techniques have not been described or shown in detail in order not to obscure the invention. In the drawings, like numerals refer to like structures or processes.
The term "data processing system" is used herein to refer to any machine for processing data, including the computer systems and network arrangements described herein. The term "Elastic Presentation Space" ("EPS") (or "Pliable Display Technology" ("PDT")) is used herein to refer to techniques that allow for the adjustment of a visual presentation without interfering with the information content of the representation. The adjective "elastic" is included in the term as it implies the capability of stretching and deformation and subsequent return to an original shape. EPS graphics technology is described by Carpendale in "A Framework for Elastic Presentation Space" (Carpendale, Marianne S. T., A Framework for Elastic Presentation Space (Burnaby, British Columbia: Simon Fraser University, 1999)), which is incorporated herein by reference. In EPS graphics technology, a two-dimensional visual representation is placed onto a surface; this surface is placed in three-dimensional space; the surface, containing the representation, is viewed through perspective projection; and the surface is manipulated to effect the reorganization of image details. The presentation transformation is separated into two steps: surface manipulation or distortion and perspective projection.
FIG. 1 is a graphical representation 100 of the geometry for constructing a three-dimensional ("3D") perspective viewing
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frustum 220, relative to an x, y, z coordinate system, in accordance with known elastic presentation space (EPS) graphics technology. In EPS technology, detail-in-context views of two-dimensional ("2D") visual representations are created with sight-line aligned distortions of a 2D information pre- 5 sentation surface within a 3D perspective viewing frustum 220. In EPS, magnification of regions of interest and the accompanying compression of the contextual region to accommodate this change in scale are produced by the movement of regions of the surface towards the viewpoint ("VP") 10 240 located at the apex of the pyramidal shape 220 containing the frustum. The process of projecting these transformed layouts via a perspective projection results in a new 2D layout which includes the zoomed and compressed regions. The use of the third dimension and perspective distortion to provide 15 magnification in EPS provides a meaningful metaphor for the process of distorting the information presentation surface. The 3D manipulation of the information presentation surface in such a system is an intermediate step in the process of creating a new 2D layout of the information. 20
FIG. 2 is a graphical representation 200 of the geometry of a presentation in accordance with known EPS graphics technology. EPS graphics technology employs viewer-aligned perspective projections to produce detail-in-context presentations in a reference view plane 201 which may be viewed on 25 a display. Undistorted 2D data points are located in a basal plane 210 of a 3D perspective viewing volume or frustum 220 which is defined by extreme rays 221 and 222 and the basal plane 210. The VP 240 is generally located above the centre point of the basal plane 210 and reference view plane ("RVP") 30 201. Points in the basal plane 210 are displaced upward onto a distorted surface 230 which is defined by a general 3D distortion function (i.e. a detail-in-context distortion basis function). The direction of the viewer-aligned perspective projection corresponding to the distorted surface 230 is indi- 35 cated by the line FPo-FP 231 drawn from a point FPo 232 in the basal plane 210 through the point FP 233 which corresponds to the focus or focal region or focal point of the distorted surface 230.
EPS is applicable to multidimensional data and is well 40 suited to implementation on a computer for dynamic detailin-context display on an electronic display surface such as a monitor. In the case of two dimensional data, EPS is typically characterized by magnification of areas of an image where detail is desired 233, in combination with compression of a 45 restricted range of areas of the remaining information (i.e. the context) 234, the end result typically giving the appearance of a lens 230 having been applied to the display surface. The areas of the lens 230 where compression occurs may be referred to as the "shoulder" 234 of the lens 230. The area of 50 the representation transformed by the lens may be referred to as the "lensed area". The lensed area thus includes the focal region and the shoulder. To reiterate, the source image or representation to be viewed is located in the basal plane 210. Magnification 233 and compression 234 are achieved 55 through elevating elements of the source image relative to the basal plane 210, and then projecting the resultant distorted surface onto the reference view plane 201. EPS performs detail-in-context presentation of n-dimensional data through the use of a procedure wherein the data is mapped into a 60 region in an (n+1) dimensional space, manipulated through perspective projections in the (n+1) dimensional space, and then finally transformed back into n-dimensional space for presentation. EPS has numerous advantages over conventional zoom, pan, and scroll technologies, including the capa- 65 bility of preserving the visibility of information outside 234 the local region of interest 233.
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For example, and referring to FIGS. 1 and2, in two dimensions, EPS can be implemented through the projection of an image onto a reference plane 201 in the following manner. The source image or representation is located on a basal plane 210, and those regions of interest 233 of the image for which magnification is desired are elevated so as to move them closer to a reference plane situated between the reference viewpoint 240 and the reference view plane 201. Magnification of the focal region 233 closest to the RVP 201 varies inversely with distance from the RVP 201. As shown in FIGS. 1 and 2, compression of regions 234 outside the focal region 233 is a function of both distance from the RVP 201, and the gradient of the function describing the vertical distance from the RVP 201 with respect to horizontal distance from the focal region 233. The resultant combination of magnification 233 and compression 234 of the image as seen from the reference viewpoint 240 results in a lens-like effect similar to that of a magnifying glass applied to the image. Hence, the various functions used to vary the magnification and compression of the source image via vertical displacement from the basal plane 210 are described as lenses, lens types, or lens functions. Lens functions that describe basic lens types with point and circular focal regions, as well as certain more complex lenses and advanced capabilities such as folding, have previously been described by Carpendale.
System. FIG. 3 is a block diagram of an exemplary data processing system 300 for implementing an embodiment of the invention. The data processing system is suitable for implementing EPS technology and for viewing stereoscopic presentations in conjunction with a graphical user interface ("GUI"). The data processing system 300 includes an input device 310, a central processing unit or CPU 320, memory 330, and a display 340. The input device 310 may include a keyboard, mouse, trackball, or similar device. The CPU 320 may include dedicated coprocessors and memory devices. The memory 330 may include RAM, ROM, databases, or disk devices. And, the display 340 may include a computer screen or terminal device and a stereoscopic viewing device (not shown). The stereoscopic viewing device may include a pair of 3D anaglyph (i.e. red/blue, red/green, etc.) glasses or a pair of 3D shutter glasses with supporting hardware and software. The display 340 may also include split level screens. The data processing system 300 has stored therein data representing sequences of instructions which when executed cause the method described herein to be performed. Of course, the data processing system 300 may contain additional software and hardware a description of which is not necessary for understanding the invention.
Stereoscopic Detail-In-Context Presentations from Monoscopic Images. FIG. 5 is a graphical representation 500 of the geometry for constructing stereoscopic perspective viewing frustums in accordance with an embodiment of the invention. In FIG. 5, the right-eye and left-eye viewpoints 541,542 lie at the apex of right-eye and left-eye perspective viewing frustums 521, 522, respectively. The right-eye and left-eye viewpoints 541, 542 are spaced by an "eye separation" distance 501.
According to an embodiment of the invention, stereoscopic detail-in-context presentations are generated from monoscopic images. In general, a monoscopic representation of a 3D object is rendered or presented stereoscopically by rendering the representation twice, once from a right-eye viewpoint 541 and once from a left-eye viewpoint 542. If no lens is applied to the representation, the right and left renderings are generally the same (i.e. for images that are not stereo pairs). If a lens is applied, the required point displacements are calculated by software stored in the data processing sys
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