Systems and methods for turning pages in a three-dimensional electronic document

BACKGROUND

It is becoming increasingly popular to read in electronic form documents that have traditionally been available only in paper form, such as magazines, journals, such as trade journals and scientific journals, textbooks, photographic albums, newspapers and the like. However, many readers are reluctant to read these documents in electronic form because the electronic documents lack characteristics of paper documents to which the readers have become accustomed.

Techniques replicating characteristics of paper documents in electronic documents (also referred to herein as "virtual books") is highly desirable. Virtual books may include a broad range of documents and include simulations of physical books such as magazines, journals, textbooks, photograph albums, newspapers or the like. Virtual books can be displayed by e.g., e-book systems, personal computers (PCs), personal digital assistants (PDAs), or the like.

Virtual book display systems, e.g., e-book systems, PCs, PDAs, or the like display virtual books in a two-dimensional ("2D") manner or a three-dimensional ("3D") manner. For example, B. Harrison describes several 2D-based e-book devices in "E-Books and the Future of Reading", IEEE Computer Graphics and Applications, Vol. 10, No. 3, pages 32-39. It will be appreciated that, as used throughout the present disclosure, "three-dimensional" typically refers to implementation of a three-dimensional appearance of an object on a two-dimensional display, e.g., the display screen of a computer or the like.

Modem graphics systems provide ways to represent virtual books on a computer screen by creating a 3D appearance of a physical book. Displaying virtual books in a 3D manner provides a more realistic appearance of an actual physical book when compared to displaying virtual books in a 2D manner. 3D virtual books have many potential uses, such as, for example, the representation of historical manuscripts, the representation in electronic bookstores of books for sale, electronic book publishing, the basis of new forms of medical textbooks and other enhanced book formats, new forms of laboratory journals, and photograph albums.

A limitation on the ability of a virtual book to appear to a viewer as an actual physical book is at times limited to the appearance of the page while the page is being turned along with the page turning technique used by a virtual book display system. Realistic page turning can give readers and viewers the impression of reading or viewing an actual physical book. Since page turning is a dynamic animation that not only starts, but also finishes with the book in a static opened or closed position, both how the static positions of the book are represented and how the dynamic positions of the book are represented affects, to a large degree, how the book should be represented during the page turning animation, and vice versa.

There are various e-book systems for displaying electronic documents in a 3D manner. For example, U.S. Patent 6,340,980 describes a special user interface device mimicking an actual physical book. When connected to a computer, this device works like any other user interface device such as a mouse. A software product, known as the Flip Browser®, has been developed by E-Book Systems Inc., and can be found at http://www.flipbrowser.com.

Additionally, U.S. Patent Application Publication No. 20020035697 describes systems and methods for distributing and viewing electronic documents. A software product, known as the Zinio Reader®, has been developed by Zinio Systems Inc., and can be found at http://www.zinio.com. Another system, the Turning the Pages® system is based on a multimedia authoring product called Macromedia. The Turning the Pages® system is jointly developed by the British Library and Armadillo Systems, and can be found at http://www.bl.uk/whatson/exhibitions/lindisfarne/ttp.html. Although the above describe and/or display electronic documents in a 3D manner, the disclosures regarding the page turning feature for virtual books displayed in a three-dimensional manner are limited to little or no detail of how the page turning features are designed or implemented.

U.S. Patents 5,847,709 and 5,838,326 describe another system, commercially known as the WebBook® developed by Xerox Corporation, for displaying electronic documents in a three-dimensional manner. Although the page turning animation of the WebBook® appears very similar to the page turning of an actual physical book, there are several drawbacks.

For example, an opened virtual book only models the top faces of the book, not the back side. Therefore, in a virtual environment where the back side or bottom faces, such as, for example, the front and back covers, of an opened virtual book are invisible to the virtual camera, the virtual book may no longer resemble an actual physical book. A virtual camera is an imaginary device that may correspond to the screen or a reader's view of the screen. The virtual camera displays the reader's view of the object, e.g. a virtual book, shown on the screen. Transitioning between a closed book and an opened book requires changing between the closed book representation and the opened book representation.

U.S. Patent Application No. 10/739,175, the disclosure of which is incorporated herein by reference in its entirety, discloses a method for turning pages of a 3-dimensional electronic document having a predetermined length, a predetermined width and a predetermined thickness. The method may include, selecting a number of pages of the 3-dimensional document to be turned, each of the pages having a predetermined thickness; animating, relative to predetermined coordinates of a static base line, movement of a first 3-dimensional object, a second 3-dimensional object connected to the first 3-dimensional object at a first connection point, and a third 3-dimensional object connected to the second 3-dimensional object at a second connection point; and maintaining the first connection and the second connection while animating the movement of the first 3-dimensional object, the second 3-dimensional object and the third 3-dimensional object.

Additionally, WebBook® include a page ruffling technique that simulates the multiple concurrent turning of a set of pages of the WebBook®. The pages to be turned are represented by multiple turning pages blocks. However, although the page ruffling technique provides the capability to rapidly scan through a set of pages for information of interest, the ruffling technique requires that the textures of all of the pages being turned be displayed. The texture of the page includes the images shown on the page and may include both low and high resolution images. Therefore, in WebBook®, all of the page textures are pre-loaded and stored in the main memory. Pre-loading and storing all of the page textures in the main memory severely limits the scalability of the system and restricts the number of pages allowed in a virtual book. Furthermore, it is difficult to determine, even approximately, the amount of pages being turned during the page ruffling. <u style="single">SUMMARY</u>

It is desirable to implement a page turning feature in a virtual book displayed in 3D that can realistically represent the turning of pages of an actual physical book.

Exemplary embodiments of this invention provide systems and methods that allow the pages of 3D virtual books to be turned forwards or backwards in a manner that represents the turning of pages of an actual physical book.

Exemplary embodiments provide systems and methods that allow a left side pages block and a right side pages block of a 3D virtual book to be moved relative to a top face base line.

Exemplary embodiments provide systems and methods that allow a turning pages block of a 3D virtual book to be moved relative to a top face base line and a geometric shaped object.

Exemplary embodiments provide systems and methods that turn the pages of a 3D virtual book forward or backward in a manner that realistically represents turning pages of an actual physical book. The pages being turned are may be merged with the pages located in the left side or the right side of the opened 3D virtual book without producing a visual discontinuity.

In exemplary embodiments, the top, bottom, left, right, front and/or back faces of a turning pages block of the 3D virtual book is modeled as having curved surfaces.

In exemplary embodiments, an opened 3D virtual book is modeled as a left side pages block and a right side pages block. The left side pages block represents the left side of an opened book with respect to the book binding while the right side page block represents the right side of an opened book with respect to the book binding. When the book is opened, these two blocks may be connected at a common boundary and have top faces which lie on a top face base line. Just prior to pages being turned, another 3D object representing a turning pages block is created in the left or right side pages block in order to represent the portion of the pages to be turned. Throughout the page turning animation, the left side pages block, the turning pages block and the right side pages block gradually rotate, translate and/or deform relative to the top face base line and geometric shape while maintaining common connection points. Moreover, throughout the page turning animation, the turning pages block deforms by curling around the imaginary geometric object. Curling is a process by which the points of the turning pages block are mapped to corresponding points on the geometric object. The size of the geometric object may change as the turning pages block rotates from one side of the book to the other side of the book. The rotation, translation, and/or deformation of the left side pages block, the turning pages block and the right side pages block produce a realistic effect of page turning in the 3D virtual book. At the end of the page turning animation, the turning pages block is merged into either the left side pages block or the right side pages block of the 3D virtual book to return the book to a static state. In one embodiment of the method as defined in claim 1, the three-dimensional object is an electronic document, and the turning portion includes at least one page of the electronic document. In a further embodiment the turning portion comprises multiple pages of the electronic document, turned as a single block. In a further embodiment a size of the single block is determined based on user input indicating a number of pages to be turned at once. In one embodiment of the method as defined in claim 6, the three-dimensional object is an electronic document, and the turning portion includes at least one page of the electronic document. In a further aspect, the invention provides a computer readable storage medium on which is recorded a set of instructions for performing the method of claim 6. In a further aspect the invention provides a system including the controller of claim 10.

These and other features and advantages the invention are described in or are apparent from the following detailed description of the systems and methods of various exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be described in detail, with reference to the following figures in which like reference numerals refer to like elements and wherein:

Figure 1 illustrates an embodiment of a virtual environment containing three-dimensional electronic books, some displayed in an opened position and some displayed in a closed position;

Figure 2 illustrates a cross-section of a three-dimensional electronic book of Figure 1 in a closed position;

Figure 3 illustrates a cross-section of a three-dimensional electronic book of Figure 1 in an opened position;

Figure 4 illustrates a cross-section of exemplary page turning to rotate the book's pages in a three-dimensional electronic book of Figure 1;

Figure 5 illustrates an environment of a virtual environment containing a three-dimensional electronic book in an opened position;

Figure 6 illustrates a cross-section of the three-dimensional electronic book of Figure 5 in a closed position;

Figure 7 illustrates a cross-section of the three-dimensional electronic book of Figure 5 in an opened position;

Figure 8 illustrates a cross-section of exemplary page turning to rotate a turning pages block in the three-dimensional electronic book of Figure 5;

Figure 9 illustrates an embodiment of a closed three-dimensional electronic book;

Figure 10 illustrates a cross-section of the three-dimensional electronic book of Figure 9 in a closed position;

Figure 11 illustrates an exemplary embodiment of a virtual environment containing an opened three-dimensional electronic book;

Figure 12 illustrates a static state cross-section of page turning of the three-dimensional electronic book of Figure 11;

Figure 13 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 including a turning pages block at the beginning of forwarding pages;

Figure 14 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 rotating the turning pages block 45 degrees counter-clockwise;

Figure 15 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 rotating the turning pages block 90 degrees counter-clockwise;

Figure 16 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 rotating the turning pages block 135 degrees counter-clockwise;

Figure 17 illustrates exemplary embodiment of page turning of the three-dimensional electronic book of Figure 11 rotating the turning pages block 180 degrees counter-clockwise;

Figure 18 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 at the end of rotating the turning pages block;

Figure 19 illustrates exemplary embodiment of page turning, including deforming a turning pages block by mapping a point of the turning pages block to a point on an imaginary geometric shape;

Figure 20 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 using the imaginary geometric shape shown in Figure 19;

Figure 21 illustrates exemplary page turning of the three-dimensional electronic book of Figure 11 using the imaginary geometric shape shown in Figure 19 to rotate the turning pages block counter-clockwise;

Figures 22 and 23 illustrate exemplary states of the three-dimensional electronic book of Figure 11 at the end of rotating the turning pages block;

Figure 24 illustrates an exemplary embodiment of a frame of a page turning animation at a time using the imaginary geometric shape shown in Figure 19;

Figure 25 illustrates an exemplary embodiment of a frame of a page turning animation at another time using the imaginary geometric shape shown in Figure 19;

Figure 26 is a flow chart outlining an exemplary method for turning pages of a three-dimensional electronic document;

Figure 27 is a flow chart outlining an exemplary method for displaying a turning pages block with respect to the coordinates of a base line and a side of an imaginary geometric object located in a plane perpendicular to the base line of the opened three-dimensional electronic document;

Figure 28 is a flow chart outlining an exemplary method for determining coordinates of points of a left side pages block, a right side pages block and a turning pages block; and

Figure 29 is a block diagram outlining an exemplary embodiment of a system for turning and displaying pages of a three-dimensional electronic document.

DETAILED DESCRIPTION

Although the page turning techniques of 3D virtual books may appear somewhat similar to the page turning of actual physical books, there are several shortcomings in the page turning features of 3D virtual books. For example, as shown in Figure 1, a virtual environment 100 containing 3D virtual books, such as WebBooks®, looks reasonably realistic when a closed virtual book 110 or the top faces 122,124 of an opened virtual book 120 are viewed with a virtual camera. In WebBook®, a closed virtual book 110 models the top face and part of the bottom face of the book, while an opened virtual book 120 models the top faces 122,124 of the book.

Figure 2 shows the cutting plane of a closed WebBook®, taken at line A-A in Figure 1, as a rectangular box ABCD. Figure 3 shows the cutting plane of an opened WebBook®, taken at line B-B in Figure 1, as line A-S (including line segments A-B, B-C, C-D, etc.), respectively. The book cutting plane is where the book is cut in half in a direction perpendicular to the front and back faces, e.g., covers, of the book. As shown in Figure 3, the opened virtual book 120 models the top faces 122,124 of the book and not the back side. In a virtual environment displaying an opened virtual book, the back side or bottom faces, such as, for example, the front and back covers, are not visible to the virtual camera. Transitioning between a closed book 110 and an opened book 120 requires changing between the closed book representation of Figure 2 and the opened book representation of Figure 3.

Figure 4 shows modeling of a turning pages block 126 representing the pages of the WebBook® being turned. As the turning pages block 126 rotates in the direction of arrow 130, point J moves in the direction of arrow 140 until the turning pages block has turned 90 degrees from an initial starting position. Point J then travels back in a direction opposite to arrow 140 until the turning pages block 126 has rotated 180 degrees from the initial starting position.

The WebBook® also includes a page ruffling technique (not shown) that simulates the multiple concurrent turning of a set of pages of the WebBook®. The pages to be turned are represented by a turning pages block. However, although the page ruffling technique provides the capability to rapidly scan through a set of pages for information of interest, the ruffling technique requires that the textures of all of the pages being turned to be displayed. Therefore, in WebBook® all of the page textures are pre-loaded and stored in the main memory. Pre-loading and storing all of the page textures in the main memory severely limits the scalability of the system, restricting the number of pages allowed in a virtual book. Furthermore, it is difficult to determine, even approximately, the number of pages being turned during the page ruffling.

Other three-dimensional virtual books have also attempted to model turning the pages of an actual physical book. For example, Figure 5 shows a virtual environment 200 containing a three-dimensional virtual book in an opened position 220 with pages on the left and right sides 222, 224. Figure 6 shows the cutting plane, of the three-dimensional electronic book in a closed book position 210, as a rectangle ABCD. The virtual book also has a static base line 228 along line A-B and located at a bottom plane of the book in the closed position 210. The static plane is used during page turning as a static reference line that assists in determining the relative movement of the pages of the virtual book. The terms "front" and "back" refer to the side of the cutting plane where the front cover and the back cover are located, respectively. A reader may view the front side from a plane perpendicular to the front side.

Figure 7 shows the cutting plane, taken at line C-C in Figure 5, of the three-dimensional book in the opened position 220. As shown in Figure 7, an opened virtual book is modeled as at least a left side pages block 222 and a right side pages block 224 represented by rectangular polygons ABCD and BEFG, respectively. The static base line 228, corresponding to line A-E, located at a bottom plane of the opened book 220, is used during page turning as a static reference line that assists in determining the relative movement of the pages of the virtual book.

Figure 8 shows modeling of a turning pages block 226 representing the pages of the virtual book being turned. During the page turning animation, the bottom faces, corresponding to lines A-B and B-E, of the left side pages block 222 and the right side pages block 224, respectively, remain stationary on the base line 228, and the turning pages block 226 rotates in the direction of arrow 230 around the connection point J,H.

Modeling the three-dimensional virtual book as rectangles positioned relative to the bottom face base line 228 contains several drawbacks. First, the dropping of the turning pages block 226 at the end of the animation leads to a visual discontinuity. Second, as the virtual book is turned from one page to another, the locations of the top faces of the left side pages block 222 and the right side pages block 224 change dynamically. This means that the relative distances between a static camera and the top pages of the virtual book are not constant, which makes the top pages of the opened book appear as different sizes depending on which two pages are being displayed. Third, as the pages are turned, the pages remain flat or are deformed unrealistically.

The following detailed discussion is directed to specific applications, namely three-dimensional electronic books, with which the exemplary embodiments of page turning systems and methods of this invention are usable. However, it should be appreciated that this is for the ease of understanding and familiarity only, and should not be interpreted as limiting the types of applications with which the systems and methods of the exemplary embodiments are usable.

Page turning methods and systems include two concurrent processes, namely 1) a rotation process and 2) a deformation process. The rotation process gradually rotates a page or group of pages, referred to as a turning pages block, around a fulcrum, such as a virtual book binding from one side of a book to the other side of a book along a page turning travel path. The page turning travel path includes the locus of the different locations of the page as the page rotates around a fulcrum from one side of a book to the other side of a book . It should be appreciated that the fulcrum need not be fixed, but may move, as described above with reference to Figure 4. During the rotation process the part of the page block attached to the book binding, e.g., the turning pages block's left side (as when a page block is turned from a right side of a book to the left side of a book), is viewed by a reader as stationary while the remaining part of the page block is moved. In the example shown in Figures 14-16, the cross-section of the page block, i.e., parallelogram JKGC, viewed in a plane perpendicular to a reader's view of a front side of the book, is viewed as rigid and unrealistic. The deformation process, in exemplary embodiments of the invention, is directed to creating a more realistic view of the turning pages block, i.e., parallelogram JKGC, by realistically deforming the turning pages block during page turning.

In the deformation process of exemplary embodiments, the turning pages block is curled around an imaginary geometric shape, such as, for example, a cone. The geometric shape's size may change as the page travels along a travel path from one side of the book to the other side of the book to produce various curved shapes at different frames, i.e., different points along the page turning path. When the rotation process and deformation process are concurrently operated the cross-section of the turning page a block, i.e., curved object JKGC shown in Figure 21, is viewed by a reader as flexible. As such, the page turning is more realistic.

Figure 9 illustrates an exemplary embodiment of a three-dimensional electronic book 300 in a closed position 310. Figure 10 illustrates the cutting plane of the exemplary embodiment of the three-dimensional electronic book of Figure 9 taken at line D-D. Since the length of the virtual book 300 is the length of an individual page such as, for example, the distance between the top of the page and the bottom of the page, the length of the virtual book 300 remains constant throughout the page turning animation.

As illustrated in Figure 10, the closed book 310 is represented as a parallelogram ABCD. The terms "front" and "back" refer to the side of the cutting plane where the front cover and back cover are located, respectively. A reader may view the "front" side from a plane above the front side. The width of the book, e.g., the length of lines A-B and D-C, may be determined by the width of an individual page, or by the width of the front or back cover. The thickness of the book, e.g., the shortest distance between line D-A and line C-B, is determined by the thickness of the cumulative number of pages in the book, and the thickness of the front and back covers. The slanting angles ABC and ADC may be predefined constants. The virtual book 300 may also have a static base line 320, corresponding to line DC and located at a top plane, e.g., front face, of the closed book 310, which is used during page turning as a static reference line that assists in determining the relative movement of the pages of the virtual book 300. <b>[PLEASE CONFIRM THE LOCATION OF THE STATIC BASE LINE, THE STATIC BASE LINE IS AT THE <u style="single">BOTTOM</u> IN FIGURE 6]</b>

Figure 11 illustrates an exemplary embodiment of the three-dimensional electronic book 300 of Figure 9 in an opened position 330 and displays the three-dimensional electronic book 300 in a perspective view showing the thickness of the left side 332 and the right side 334 of the book 300. The thickness of the left side 332 and right side 334 of the book 300 represents the number of pages on the left and right sides 332,334 of the opened book 330, respectively. Figure 12 illustrates the cutting plane, taken at line E-E in Figure 11, of the exemplary embodiment of the three-dimensional electronic book 300 in the opened position 330. In Figure 12 static base line 320 corresponds to line E-E in Figure 11 and the front face of the pages being viewed.

As illustrated in Figure 12, a static state of the exemplary embodiment of the three-dimensional electronic book 300 in the opened position 330 of Figure 11 is modeled as including at least two pages blocks. Specifically, the left side pages block 332 is represented by a parallelogram ABCD, and the right side pages block 334 is represented by another parallelogram EFGC. While parallelograms are depicted, it is not necessary that the pages blocks be parallelograms. In this and other figures, more relaxed shapes are also acceptable. The left side pages block 332 and the right side pages block 334 connect at point C. Point C corresponds to the book binding. Similar to the virtual book 300 in the closed position 310, shown in Figure 9, the width of the left side pages block, corresponding to line A-B, and the width of the right side pages block, corresponding to line E-F, may be determined by the width of an individual page. Also, similar to the virtual book 300 in the closed position 310, as shown in Figure 9, the thickness of the left side pages block, e.g., the distance between line D-A, and the thickness of the right side pages block, e.g., the distance between line C-E, may be determined by the thickness of an individual page and the cumulative number of pages in each of the blocks. The static base line 320 of the virtual book 300 may be located at a top plane corresponding to the top faces of the book as viewed by a reader and may correspond to line DCG of the opened book 330. The static base line 320 may be used during page turning as a static reference line and assists in determining the relative movement of the pages of the virtual book 300. The terms "front" and "back" refer to the side of the cutting plane a reader views. For example, in the embodiment shown in Figure 12, a reader views the open pages of the book when the book is viewed from the "front" side. The "back" side, on the other hand, is hidden from the viewer's view.

The dimensions mentioned above are intrinsic properties of the book calculated and/or determined by various methods and systems known to those skilled in the art. For example, since a length, a width and a thickness of an individual page of the closed virtual book may be predetermined, a thickness of the closed virtual book may also be predetermined and equal to total number of pages in the closed virtual book multiplied by the thickness of the individual page. A value can be added to the thickness calculation to account for the cover, along with other parts of a book, e.g., pages, that may have a thickness different than an individual page. Additionally, since the number of pages in the left side pages block and the right side pages block during the static state of Figure 12 may be predetermined, the coordinates or points of the left side pages block and the right side pages block relative to the static base line may also be predetermined. Further, the location of the virtual book in the virtual environment is also predetermined. Since many dimensions and coordinates are predetermined, when a book is selected by the reader for viewing, the geometry of the book, such as, for example, the coordinates of the points of the blocks in Figures 10 and 12 and the location of the static base line are preferably predetermined. Therefore, the reader only needs to select the virtual book to be viewed and the number of pages of the virtual book to turn forwards or backwards.

The following detailed description illustrates an embodiment of a sequence of positions of the pages as the pages of the three-dimensional electronic book 300 of Figure 9 are rotated. The exemplary embodiment illustrates rotating pages of a virtual book in a forward or counter-clockwise direction; however, it should be appreciated that the pages of the virtual book can also be rotated in a backward or clockwise direction, or other directions depending on the location of the book binding. It should also be appreciated that one or more pages of a book can be rotated at the same time.

Before rotating the pages of the book forward (e.g., in a counter-clockwise direction), the number of pages to be turned is determined. The page turning system determines a portion, representing the number of pages to be turned, of the right side pages block 334 that needs to be turned from the right side of the book to the left side of the opened virtual book 330.

Figure 13 illustrates the beginning of the page rotating animation of the virtual book 330 with the pages in an initial page turning position. First, the right side pages block 334 is split into a first portion representing the number of pages to be turned and a second portion representing the pages that remain in the right side pages block after the first portion has been removed. The first portion is a turning pages block 338 represented by the parallelogram JKGC. The thickness, e.g., the distance between line J-K and line C-G, of the turning pages block 338, may be determined by multiplying the number of pages to be turned and the thickness of an individual page. Further, the second portion, a new right side pages block 336, represented by parallelogram EFIH, illustrates the difference between the previous right side pages block 334 and the turning pages block 338. The second portion is not turned in this animation. Finally, the top face, corresponding to line D-C of the left side pages block 332, and the top face, corresponding to line C-G of the turning pages block 338, may be co-linear with the static base line 320.

Figures 14-17 illustrate exemplary states of the 180 degrees counter-clockwise rotation of the turning pages block 338 in which the turning pages block has rotated 45, 90, 135, and 180 degrees counter-clockwise, respectively, with regard to the initial starting position of Figure 13. During the rotation of the turning pages block 338, the top face corresponding to line D-C of the left side pages block 332 and the top face corresponding to line C-G of the turning pages block 338 do not line up with the static base line 320. The following discussion describes the movement of the left side pages block 332, the right side pages block 336, and the turning pages block 338 in greater detail.

As illustrated in Figures 14-17, the turning pages block 338 rotates, in the direction of arrow 340, around the point J,H. At the same time, the point J,H starts to move towards the static base line 320 along an upward direction towards the position where point C was located at the beginning of the animation, i.e., along the direction of line J-C of Figure 13. However, throughout the animation, the left side pages block 332 and the turning pages block 338 remain connected at point C resulting in a downward translation 350 of the left side pages block 332 away from the static base line 320. Similarly, concurrent with the movement of the left side pages block 332, the right side pages block 336 and the turning pages block 338 remain connected at the point J,H which results in an upward translation 360 of the right side pages block 336 towards the static base line 320.

As the page turning animation proceeds, the slanting angle CJK of the turning pages block 338 gradually changes from an obtuse angle in Figure 13 into an acute angle in Figure 16. However, the thickness, i.e. the distance between lines C-J and G-K, of the turning pages block 338 remains constant.

As shown in Figure 17, after the turning pages block 338 has rotated 180 degrees counter-clockwise from the initial page turning position, the side faces corresponding to lines B-C and A-D the left side pages block 332 may become collinear with the side faces corresponding to lines C-J and G-K of the turning pages block 338, respectively. Additionally, the top face corresponding to line K-J of the turning pages block 338 and the top face corresponding to line J-I of the right side pages block 336 may be collinear with the static base line 320.

Figure 18 illustrates a modeling of the exemplary embodiment of the three-dimensional electronic book 300 in an opened position at the end of the page turning animation. As shown in Figure 18, a new left side pages block 370 is created as a result of merging the turning pages block 338 with the left side pages block 332 of Figure 17. Thus, the top face corresponding to line K-J of the new right side pages block 370 and the top face corresponding to line J-I of the right side pages block 336 are collinear with the static base line 320.

The embodiments disclosed in Figures 14-16 show a rigid turning pages block 338. However, as discussed above, when the techniques disclosed in Figures 14-16 are used to turn a page, a somewhat unrealistic page turning effect is created because the turning pages block front surface, as viewed by a reader viewing the turning pages block face, remains as a flat surface during page turning. Because the flat surface of the turning pages block 338 does not deform during page turning, the turning page block 338 appears rather rigid and does not appear as a piece of paper would appear if turned in an actual physical book.

As discussed above, it is possible to create a more realistic page turning effect by creating a set of page shapes at a preprocessing stage corresponding to different points along a page turning path, and applying a preprocessed page shape to an individual page as it is rotated. For example, if the turning pages block 338 was turned in an actual, physical, book, the turning pages block would have a different geometric shape corresponding to different points along a traveled path as the turning pages block 338 traveled from one side of the book, such as, the right side pages block 334 to the other side of the book, such as, the left side pages block 332. During page turning, the set of pre-computed page shapes can be applied to a page to derive a specific page shape (i.e., a "turning" page shape) at a specific frame corresponding to a specific point of page turning as the page turns from one side of the book to the other side of the book. The set of page shapes can be constructed by a person of skill in the art. Alternatively, the sets of page shapes can be automatically computed based on the actual, physical shapes of pages as the pages are turned in an actual, physical, book.

In "How to Turn the Page," Proceedings of JCDL, 2003, pages 186-188, Yi-Chun Chu discloses a prototype page-turning system that animates full three-dimensional page turns. In "How to Turn the Page," dynamic page turning behavior is generated by a mass-spring model defined on a rectangular grid of particles. The prototype takes a PDF or e-book file, renders it into a sequence of PNG images representing individual pages, and animates the page-turns under user control. "How to Turn the Page" applies a cloth simulation model to paper and pre-computes the set of page turns. The cloth simulation model gives the page turns, as viewed by a reader, a "stretchy" effect which is, generally, unrealistic in the modeling of stiffer objects, such as a book's pages. Moreover, because each pre-computed turn must be superimposed on a specific page, implementation of the prototype takes from minutes to hours to calculate a single page turning. Another disadvantage of the method disclosed in "How to Turn the Page" is that the method does not take into account how the shapes of the turning page deform or the manner by which a page turns as a function of where on the page a reader touches.

A turning page should possess certain characteristics and/or properties when viewed by a reader. These "turning page" properties should be preserved when a page is turned in a virtual book in order to provide a realistic page turning effect and keep the page turning effect natural and appealing to the reader. The properties of a "turning page" that should be preserved as the page is turned include 1) maintaining the smoothness of the curved page as the curved page is turned, 2) maintaining the smoothness of the turning technique, 3) maintaining right angles at the corners of the page being turned, 4) minimizing the stretching or compressing of the page as it is turned, and 5) gradually changing the page shape according to where on the page the page is initially lifted in the act of page turning. By maintaining these properties and applying the computed page shape to a specific frame "on the fly," it is possible to deform a flat page into a curved shape and preserve the look and feel of a page being turned in an actual physical book.

Figure 19 illustrates page turning including rotation and deformation of the turning pages block 338. In Figure 19, the top face of a turning page block 338 corresponds to the xy-plane. The x-axis corresponds to the base line, which may be static. The bottom part of turning pages block 338, corresponding to line C'-G', aligns with the x-axis. The left side of the turning page block 338, corresponding to line S-C', aligns with the y-axis. A three-dimensional cone 400 is placed on the xy-plane. In this example, the side of the cone corresponding to line V-S may be placed parallel and touching the y-axis. As such, the cone's axis (not shown), in this example, is not parallel with the xy-plane; however, the axis is preferably in a plane with the y-axis. The side of the axis corresponding to line S-V may be modeled to correspond to a book binding and hold the edge of the turning pages block 338 corresponding to the book binding still, or allow the binding to move as shown in Figure 4, as the turning pages block rotates from one side of the book to the other side of the book.

A reader turns the page block 338 by touching a point of the page block 338, such as, for example, point G'. The "touching" may be done by physically touching the display screen, if touch screen technology is used, or by, e.g., pointing and clicking using a mouse. After the reader has touched G', the page block 338 begins deforming by curling around the outer side of the cone 400. The curling of the turning pages block 338 around the outer side of the cone 400 results in a curved page. The cone angle θ and the cone apex V (0,V_y,0) can be varied over an animation time t' to obtain different views of a turned page, i.e., different curved pages. The animation time t' corresponds to the total time required for turning the turning pages block 338 from one side of the book, corresponding to the right side pages block 336, to the other side of the book, corresponding to the left side pages block 332.

Prior to turning a page, e.g., prior to a reader touching point G' in order to turn the turning pages block 338, the cone angle θ in this example equals 90 degrees. As such, there is no page curling around the cone 400 or, as may be alternatively understood, the page curling around the cone 400 is flat. As the page turning progresses, the cone angle θ and the location of cone apex V gradually changes. The cone angle θ and the location of cone apex V correspond to the location of the turning pages block 338 as the turning pages block 338 rotates from the right side pages block 336 to the left side pages block 332.

For example, as the turning pages block 338 rotates from the right side pages block 336 to the left side pages block 332, the cone angle θ gradually falls from 90 degrees at the beginning of the page turning animation to a minimum cone angle θ once half of the page deformation has occurred. The minimum cone angle 8 and/or the point equal to one-half of the page deformation may coincide with half of the total animation time t'. As the cone angle θ begins to change, the location of cone apex V on the y-axis moves down the y-axis in direction of arrow R towards negative infinity. Because the points of the turning pages block 338 are mapped to corresponding points on the imaginary cone 400, as the cone's shape changes (e.g., as the cone's angle θ and apex location V change), the turning pages block 338 is deformed as the points of the turning pages block 338 are mapped to a different shaped cone 400 in each successive frame of the page turning animation. Thus, as point P is mapped from one cone shape to the next, the page curls up from the xy-plane about the outer side of the cone 400 with its lower right corner corresponding to G' lifted first. As such, G' is deformed and turned ahead of the rest of the turning pages block 338.

After turning page block 338 reaches the halfway point of the deformation process, the cone angle θ gradually increases to 90 degrees and the cone apex V translates in the direction opposite to the direction of arrow R. Thus, in the deformation process, the cone angle θ at first gradually decreases from 90 degrees to a minimum cone angle θ and the cone apex V translates in the direction of arrow R along the y-axis towards negative infinity. Then, upon the deformation process reaching a halfway point, the cone angle θ and cone apex location V simultaneously reach minimum values, whereupon the cone angle θ begins increasing towards 90 degrees and the cone apex location V reverses direction opposite to the direction of the arrow R and heads toward the xy origin. Thus, in exemplary embodiments, the second half of the deformation process can be a mirror image of the first half of the deformation process.

For example, as shown in Figure 19, a given point P (P_x,P_y,0) on page block 338 maps to a specific point on the cone 400. The specific point on the cone 400 that point P maps to can be calculated by drawing a circle of radius <maths id="math0001" num=""><math display="inline"><mrow><mi>R</mi><mo>=</mo><mrow><mo>|</mo><mrow><mi>A</mi><mi>P</mi></mrow><mo>|</mo></mrow><mo>=</mo><msqrt><mrow><msubsup><mi>P</mi><mi>x</mi><mn>2</mn></msubsup><mo>+</mo><msup><mrow><mrow><mo>(</mo><mrow><msub><mi>P</mi><mi>y</mi></msub><mo>−</mo><msub><mi>A</mi><mi>y</mi></msub></mrow><mo>)</mo></mrow></mrow><mn>2</mn></msup></mrow></msqrt></mrow></math><img file="EP1672474A2_D0001.tif" /></maths>around V on the xy-plane, where R corresponds to the length of line A-P. The intersection between the circle and the y-axis is denoted as point S. Based on cone geometry, as turning pages block 338 is wrapped around the cone 400, arc <maths id="math0002" num=""><math display="inline"><mrow><mover accent="true"><mrow><mi>S</mi><mi>P</mi></mrow><mo stretchy="true">^</mo></mover></mrow></math><img file="EP1672474A2_D0002.tif" /></maths>coincides with a circular cross section that is parallel to the base of the cone and intersects point S. Given that point P maps to point T on the cone's cross section, <maths id="math0003" num=""><math display="inline"><mrow><mrow><mo>|</mo><mrow><mover accent="true"><mrow><mi>S</mi><mi>T</mi></mrow><mo stretchy="true">^</mo></mover></mrow><mo>|</mo></mrow><mo>=</mo><mrow><mo>|</mo><mrow><mover accent="true"><mrow><mi>S</mi><mi>P</mi></mrow><mo stretchy="true">^</mo></mover></mrow><mo>|</mo></mrow><mo>.</mo></mrow></math><img file="EP1672474A2_D0003.tif" /></maths>Denoting the center of the cross section as C and the angle <i>∠SCT</i> as <i>β</i> , the following formula is developed: <maths id="math0004" num=""><math display="block"><mrow><mi>β</mi><mo>=</mo><mfrac><mrow><mrow><mo>|</mo><mrow><mover accent="true"><mrow><mi>S</mi><mi>T</mi></mrow><mo stretchy="true">^</mo></mover></mrow><mo>|</mo></mrow></mrow><mi>r</mi></mfrac><mo>=</mo><mfrac><mrow><mrow><mo>|</mo><mrow><mover accent="true"><mrow><mi>S</mi><mi>P</mi></mrow><mo stretchy="true">^</mo></mover></mrow><mo>|</mo></mrow></mrow><mi>r</mi></mfrac><mo>=</mo><mfrac><mrow><mi>α</mi><mi>R</mi></mrow><mrow><mi>R</mi><mi mathvariant="normal">sin</mi><mi>θ</mi></mrow></mfrac><mo>=</mo><mfrac><mi>α</mi><mrow><mi mathvariant="normal">sin</mi><mi>θ</mi></mrow></mfrac></mrow></math><img file="EP1672474A2_D0004.tif" /></maths> where r is the radius of the cross section and <maths id="math0005" num=""><math display="block"><mrow><mi>α</mi><mo>=</mo><mo>∠</mo><mi>S</mi><mi>A</mi><mi>P</mi><mo>=</mo><mi mathvariant="normal">arcsin</mi><mrow><mo>(</mo><mrow><mfrac><mrow><msub><mi>P</mi><mi>x</mi></msub></mrow><mi>R</mi></mfrac></mrow><mo>)</mo></mrow><mo>.</mo></mrow></math><img file="EP1672474A2_D0005.tif" /></maths>

Point T (T_x, T_y, T_z) can be computed by rotating point S around a line (x= 0, z=r) by β to point S' (S_x', S_y', S_z'), and then rotating S' around line (y=s_y, z=0) by θ. r corresponds to line C-T. Point T can be computed as <maths id="math0006" num=""><math display="block"><mrow><msub><mi>T</mi><mi>x</mi></msub><mo>=</mo><msub><msup><mi>S</mi><mo>′</mo></msup><mi>x</mi></msub><mo>=</mo><mi>r</mi><mi mathvariant="normal">cos</mi><mrow><mo>(</mo><mrow><mi>β</mi><mo>−</mo><mfrac><mi>π</mi><mn>2</mn></mfrac></mrow><mo>)</mo></mrow><mo>=</mo><mi>r</mi><mi mathvariant="normal">sin</mi><mi>β</mi><mo>,</mo></mrow></math><img file="EP1672474A2_D0006.tif" /></maths><maths id="math0007" num=""><math display="block"><mrow><msub><mi>T</mi><mi>y</mi></msub><mo>=</mo><msub><msup><mi>S</mi><mo>′</mo></msup><mi>y</mi></msub><mo>−</mo><msub><msup><mi>S</mi><mo>′</mo></msup><mi>z</mi></msub><mi mathvariant="normal">sin</mi><mi>θ</mi><mo>=</mo><mi>R</mi><mo>+</mo><msub><mi>V</mi><mi>y</mi></msub><mo>−</mo><mi>r</mi><mrow><mo>(</mo><mrow><mn>1</mn><mo>−</mo><mi mathvariant="normal">cos</mi><mi>β</mi></mrow><mo>)</mo></mrow><mi mathvariant="normal">sin</mi><mi>θ</mi><mo>,</mo></mrow></math><img file="EP1672474A2_D0007.tif" /></maths><maths id="math0008" num=""><math display="block"><mrow><msub><mi>T</mi><mi>z</mi></msub><mo>=</mo><msub><msup><mi>S</mi><mo>′</mo></msup><mi>z</mi></msub><mi mathvariant="normal">cos</mi><mi>θ</mi><mo>=</mo><mi>r</mi><mrow><mo>(</mo><mrow><mn>1</mn><mo>−</mo><mi mathvariant="normal">cos</mi><mi>β</mi></mrow><mo>)</mo></mrow><mi mathvariant="normal">cos</mi><mi>θ</mi><mo>.</mo></mrow></math><img file="EP1672474A2_D0008.tif" /></maths>

The functions θ(t) and V_y(t) may be empirically constructed to ensure a smooth animation. The combination of the rotation and deformation of the turning pages block is discussed in detail below.

Figures 20-23 illustrate exemplary states of the 180 degrees counter-clockwise rotation and deformation of the turning pages block 338 during page turning animation in which the turning pages block rotates in a counter-clockwise direction, with regard to the initial starting position shown in Figure 13. The following discussion describes the movement of the left side pages block 332, the right side pages block 336, and the turning pages block 338 in greater detail.

As shown in Figure 19, a geometric shape, such as a circular cone 400, is located on the xy-plane. The side of the cone touches the xy-plane along the y-axis and at point C'. Figure 20 illustrates a view of a cutting plane through the left side and right side of an opened book. As can been seen from Figure 20, even though the cone 400 is circular, the view of the cone 400 would be slightly elliptical since the view of the cone is not parallel with the cone's axis. The side of the cone located along the y-axis and modeled to touch the y-axis at point J in Figure 20 does not move either horizontally along the x-axis, corresponding to static base line 320, or vertically along the z-axis. In this respect the cone 400 may be static like base line 320. Because the cone size, including radius length and axis length, is variable depending on the specific point during the animation time t' (i.e., the specific frame of page turning as the page turns from one side of the book to the other side of the book), the cone 400 shown in Figures 20-21 is not drawn to a specific scale. For example, because the page turning animation has not yet begun in Figure 20, the cone angle θ equals 90. The cone shown in Figure 21, on the other hand, has a cone angle θ of less than 90 degrees.

As discussed above, a specific cone shape is generated for each frame of the page turning process. The shape of the cone is determined based on factors such as where the reader initially touches the turning pages block and the specific point of rotation of the turning pages block along the page turning travel path (i.e., point during the animation time t'). For example, although the embodiments discussed throughout the specification correspond to turning pages from the lower right corner of the right side pages block, it is also possible to use the methods and systems discussed herein to turn pages from other locations on the page. For example, a right side pages block could also be turned from the upper right side of the page. In this case, the cone 400 shown in Figure 19 would be turned 180 degrees relative to the common boundary between the right side pages block and the left side pages block. The processes described herein could then be applied to create and turn a turning pages block, whereupon the upper right corner of the turning page block, e.g. point N of Figure 19, would be lifted first, and turned ahead of other points of the turning pages block.

The page turning animation refers to the cumulative frames the reader views as the turning pages block rotates and deforms from one side of a book cover, for example, as shown in Figure 20, the right side pages block 336, to the left side pages block 332, during the animation time t'. Each frame is generated based on the rotation and deformation processes and corresponds to a specific point of the turning pages block's travel path.

Figures 20-23 illustrate exemplary page turning of a three-dimensional electronic book using the technology described above in connection with Figure 19 to rotate and deform the turning pages block. Figures 20-23 illustrate a view of a cutting plane of a visual book taken along the x-axis.

Figure 20 illustrates a cross section of the pages of, e.g., Figure 11. Figure 20 shows a frame of a turning animation just prior to a turning pages block 338 being turned. Base line 320 corresponds to the top face of the left and right side pages blocks. Because the page block is not yet being turned the cone angle θ is equal to 90 degrees. As discussed above, a user touches a point on the page block to begin the page turning animation.

As illustrated in Figure 21, the turning pages block 338 rotates, in the direction of arrow 340, around point J',H'. As the turning pages block 338 rotates, point J',H' moves toward the static base line 320 along an upward direction toward the position where point C' was located at the beginning of the animation, e.g., along the direction of line J-C of Figure 13. However, throughout the animation, the left side pages block 332 and the turning pages block 338 remain connected at the point C', resulting in a downward translation 350 of the left side pages block 332 away from the static base line 320. Similarly, concurrent with the movement of the left side pages block 332, the right side pages block 336 and the turning page block 338 remain connected at the point J',H' which results in an upward translation 360 of the right side pages block 336 towards the static base line 320.

At the same time as the turning pages block 338 rotates around point J',H', the turning pages block 338 is mapped to the cone 400 and curls about the side of the cone that touches the xy-plane along the y-axis and at point G'. As discussed above with reference to Figure 19, the turning pages block 338 deforms because the points (e.g., points G' and P) of the turning pages block correspond to points on the cone 400. As the points on the cone 400 change in relation to animation time t' because the cone's shape changes (or, as may be alternatively understood, a specific shaped cone is generated for each frame of the page turning animation), the turning pages block 338 deforms by curling around the cone. As discussed above, once the page turning animation begins and the page begins to deform by curling around the cone 400, the cone's angle θ falls from 90 degrees and the cone's apex V moves in the direction of arrow R. The next page turning animation frame is then computed with a cone angle θ less than 90 degrees and a cone's apex V located farther down the y-axis.

As shown in Figure 22, after the turning pages block 338 has rotated 180 degrees counter-clockwise from the initial page turning position, the side faces corresponding to B'-C' and A'-D' of the left side pages block 332 become collinear with the side faces corresponding to lines C'-J' and G'-K' of the turning pages block 338, respectively. Additionally, the top face, corresponding to line K'-J', of the turning pages block 338, and the top face, corresponding to line J'-I', of the right side pages block 336, are collinear with the base line 320.

Figure 23 illustrates an exemplary state of the three-dimensional electronic book in an opened position 330 at the end of the page turning animation. As shown in Figure 23, a new left side pages block 370 is created as a result of merging the turning pages block 338 with the left side pages block 332 of Figure 22. Thus, the top face, corresponding to line K-J, of the new right side pages block 370, and the top face, corresponding to line J-I, of the right side pages block 336 are collinear with the base line 320.

Since the static state of the closed virtual book 310 in Figure 10 does not have a left or right side pages block, the static state of the closed virtual book 310 is considered as a special case of the static state of the opened virtual book 330 in Figure 11. In other words, in the closed virtual book 310, one of the right side pages block and the left side pages block can be considered as invisible. Thus, transitioning between a closed book 310 and an opened book 330 is similar to the transitioning between an opened book 330 in the static state of Figure 20 and the opened book 330 in the static state of Figure 23 as described above. Therefore, turning pages of a virtual book from/to an initial/final static state closed position 310 will not be discussed in detail. Thus, a reader can carry out the page turning operation (e.g., rotation and deformation) starting from a static state closed book or an opened book placed in a virtual environment. In other words, the page turning cycle starts from a book in a static state, such as, for example, as shown in Figure 20, and goes through an animation as illustrated in Figures 21 and 22, which returns the book back to another static state, such as, for example, as shown in Figure 23.

Figures 24 and 25 individually illustrate exemplary embodiments of a frame of a page during a page turning animation. Figure 24 illustrates a page rotated at approximately 45 degrees and deformed corresponding to a cone angle θ less than 90 degrees. Figure 25 illustrates a page rotated at slightly less than 90 degrees and a cone angle θ further reduced. Moreover, in the exemplary embodiment shown in Figure 25, the cone apex V is located further down the y-axis towards negative infinity, when compared to the exemplary embodiment shown in Figure 24.

Figure 26 is a flow chart outlining an exemplary embodiment of the method for representing turning pages of a three-dimensional virtual document. As shown in Figure 26, operation of the method begins in step S1000, and continues to step S1100, where a three-dimensional document to be viewed is obtained by a reader. Then, in step S1200, the selected three-dimensional document is displayed as a left side pages block connected to a right side pages block, in a static state, based on predetermined dimensions. Next, in step S 1300, a number of pages to be turned, either forwards or backwards, is selected by the reader. The selection of the number of pages may be direct or indirect. An example of direct selection is when the reader types in a number, such as "10." An example of indirect selection is when the reader simply touches a currently displayed page, and the system understands that only that page is to be turned. Operation then continues to step S 1400.

In step S1400, the movement of the left side pages block, the right side pages block, and the turning pages block is animated based on the selected number of pages and with respect to a plane formed by a static base line corresponding to a line parallel to the x-axis and a geometric object with a side placed on the y-axis. Then, in step S 1500, a determination is made whether more pages are to be turned. This determination may be based on, for example, whether all of the pages of the document have been turned or whether the page has been opened for at least a predetermined amount of time. If so, operation jumps back to step S 1300. Otherwise, operation of the method continues to step S1600, where operation of the method ends.

Figure 27 is a flowchart outlining an exemplary method for animating the movement of the left side pages block, the right side pages block and the turning pages blocks based on the selected number of pages and with respect to a base line and a geometric object.

Operation of the method begins in step S1400, and continues to step S 1405, where, e.g., the right side pages block is split into a turning pages block and a new right side pages block. As discussed previously, the turning pages block is a first portion representing the number of pages to be turned and the new right side pages block is a second portion representing the pages that remain in the right side pages block after the first portion has been removed. As previously discussed, the thickness of the turning pages block may be determined by multiplying the number of pages to be turned and the thickness of an individual page; the thickness of the new right side pages block may be the difference between the initial right side pages block and the turning pages block; and the top face of the left side page block and the top face of the turning pages block may remain collinear with the base line. Operation then continues to step S1415.

In step S 1415, an animation time t' time is set to equal the time required to turn the turning pages block from one side of the book to the other side of the book, and an animation time t is set to the current clock time (at the beginning of animation t=0). Concurrently, the coordinates of a base line are computed, as well as the coordinates of a three-dimensional shape, such as, a geometric cone having a cone angle equal to 90 degrees and a cone apex located at a specific location on the xy-axis.

Next, in step S 1420, coordinates of all points of the left side pages block, the right side pages block and the turning pages block are determined at animation time t, using e.g., the equations described above.

In step S1425, the geometric cone is placed between a left side pages block and a right side pages block, preferably such that a side of the cone is located on the y-axis.

Next, in step S 1430, a reader selects a location of a page to start page turning, and this selection is received by the system.

Then, in step S1435, the coordinates for the selected point on the turning pages block at which page turning is to begin, e.g., point G' of Figure 19, and its corresponding point on the cone, are determined based on a function of the geometry of the cone for a specific cone angle and cone apex location. Simultaneously, the coordinates of the other points on the cone that the remaining points on the turning pages block map are calculated based on the geometry of the cone.

Next, in step S1445, the coordinates of a translated/second connection point, e.g., point(s) J',H' of Figure 20, of the turning pages block are determined based on a function of the animation time t, e.g., point(s) J',H' and point C' of Figure 20, at the previous frame of the page turning animation (e.g., beginning of page turning animation), using, e.g., the equations discussed above.

Next, in step S1450, the turning pages block deforms by mapping the points (e.g., point P) of the turning pages block to their corresponding points on the cone (e.g., point T). Simultaneously, the turning pages block rotates about the virtual book binding. Because the points, e.g., J',H' and P, at an animation time t may be determined, the location of points J',H' and P, as well as the remaining points of the turning pages block, can be determined at specific point during the animation time t' whether the turning pages block moves at a relatively constant speed, or a variable speed.

In step S1455 the right side pages block, e.g., E' F' I' H' of Figure 21, is translated upward based on the movement of point(s) J',H' of the turning pages block. Right side pages block, e.g., E' F' I' H' of Figure 21, may remain connected to the turning pages block throughout the animation.

In step S1460 the left side pages block, e.g., A'B'C'D' of Figure 21, is translated downwards based on the movement of, e.g., point C', of the turning pages block and the predetermined dimensions of the left side pages block. The left side pages block, e.g., A'B'C'D', may remain connected to the turning pages block throughout the animation.

Next, in step S 1465, the left side pages block, the right side pages block and the turning pages block are displayed.

Then, in step S1470, a determination is made whether the correct animation time t is less than the predetermined amount of time t'. As discussed above, the predetermined amount of time t' corresponds to the length of time required for the turning pages block to turn from the right side pages block to the left side pages block. If so, operation continues to step S 1475. Otherwise, operation jumps to step S 1480.

In step S1475, a new cone shape (or new cone) having a cone angle and cone apex location different from the previous cone angle and cone apex location is computed. Operation then jumps back to step S 1420 where step S 1420 through S 1470 are repeated.

If, on the other hand, t is equal to or greater than t', the operation continues to step S 1480. In step S 1480, the left side pages block and the turning pages block are merged to form a new left side pages block. For example, as shown in Figures 22 and 23, a new left side pages block is created as a result of merging the turning pages block with the initial left side pages block. Thus, the top face of the new left side pages block and the top face of the new right side pages block are collinear with the static base line. Operation then continues to step S 1500 which corresponds to step S 1500 of Figure 26.

Figure 28 is a flowchart outlining in greater detail an embodiment of a method for determining coordinates of points of the left side pages block, the right side pages block, and the turning pages block at animation time t = 0. As shown in Figure 28, operation of the method begins in step S1405, and continues to step S 1406. In step S 1406, the thickness of the turning pages block is determined based on the selected number of pages to be turned and a predetermined thickness of an individual page. Then, in step S1407, the thickness of the new right side pages block is determined based on the difference between a predetermined thickness of the initial right side pages block and the thickness of the turning pages block. Next, in step S1408, initial coordinates of points of the left side pages block, the new right side pages block and the turning pages block are determined. Operation then continues to step S 1409, where operation of the method returns to step S 1415 of Figure 27.

Figure 29 is a functional block diagram outlining an exemplary embodiment of a document turning control system 500. As shown in Figure 29, the document turning control system 500 includes an input/output interface 510, a controller 520, a memory 530, and a pages block determining circuit, routine or application 540, each appropriately interconnected by one or more control and/or data buses 550. The input/output interface 510 is linked to a display device 600 by a link 610, and one or more user input devices 700 by one or more links 710.

Each of the links 550, 610 and 710 can be any known or later-developed connection system or structure usable to connect their respective devices to the document turning control system 500. It should also be understood that links 550, 610 and 710 do not need to be of the same type.

The memory 530 can be implemented using any appropriate combination of alterable, volatile or non-volatile memory or non-alterable, or fixed, memory. The alterable memory, whether volatile or non-volatile, can be implemented by using any one or more of static or dynamic RAM, a floppy disk and disk drive, a writable or rewritable optical disk and disk drive, a hard drive, flash memory or the like. Similarly, the non-alterable or fixed memory can be implemented using any one or more of ROM, PROM, EPROM, EEPROM, and gaps in optical ROM disk, such as a CD ROM or DVD ROM disk and disk drive, or the like.

The user input devices 700 can be one or more of a touch pad, a touch screen, a track ball, a mouse, a keyboard, a stylus or any known or later-developed user input devices 700 for inputting data and/or control signals to the document turning control system 500 for turning pages of the three-dimensional electronic document.

In general, the display device 600 can be any device that is capable of displaying a virtual document and the movement of a left side pages block, a right side pages block and a turning pages block according to techniques such as those discussed above.

The pages block determining circuit, routine or application 540 receives a user input, and determines the dimensions and coordinates of a closed virtual book or an opened virtual book. Then, the pages block determining circuit, routine or application 540 determines the dimensions and point coordinates of the left side pages block, the right side pages block, and the turning page block for both rotation and deformation processes at animation time t.

The exemplary embodiment of a document turning control system for turning pages of a three-dimensional electronic document according to Figure 29 may operate in the following manner.

In operation, user input is output from the user input device(s) 700 over link 710 to the input/output data interface 510 of the document turning control system 500. The user input includes information regarding the virtual document to be viewed and the number of pages to be turned forwards or backwards. Variables relating to, e.g., the changing cone shape (e.g., minimum and maximum values for cone angles and cone apex locations) may be input by the user or programmed into the pages block determining circuit, routine, or application 540. The controller 520 inputs the user input information into the pages block determining circuit, routine or application 540.

The controller 520 controls the pages block determining circuit, routine or application 540 to determine a thickness of the turning pages block based on the selected number of pages and a predetermined thickness of the individual page, and splits the right side pages block into a turning pages block and a new right side pages block. Next, the controller 520 controls the pages block determining circuit, routine or application 540 to determine the location of the static base line and geometric shape to be used in the rotation and deformation processes. Then, the controller 520 controls the pages block determining circuit, routine or application 540 to determine the point coordinates of all points defining the left side pages block, the right side pages block and the turning pages block for both rotation and deformation processes at animation time t. Next, the controller 520 controls the pages block determining circuit, routine or application 540 to map, rotate, translate and deform the left side pages block, right side pages block, and the turning pages block. Finally, the controller 520 controls the display device 600 to display the animation as the left side pages block, right side pages block, and the turning pages block rotate, translate and deform during the turning process.