Computer graphics processing and selective visual display system – Computer graphics processing
Reexamination Certificate
1997-12-18
2001-04-10
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
C345S419000, C382S288000
Reexamination Certificate
active
06215494
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the viewing of movies of objects on a computer display.
BACKGROUND OF THE INVENTION
An image object or object movie is a sequence of images of a three-dimensional object. Each image is a snapshot of an orientation of the object from a viewpoint. Production of an object movie entails acquiring or generating the sequence of images. This is typically done either by means of a camera which photographs the object from different viewpoints, or by means of a computer which renders synthetic images by simulating a camera. For computerized viewing of the object movie it is necessary that the images be in digital form. Thus if the camera used is not a digital camera, it is also necessary to digitize the images photographed, for download to a computer. Digitization is typically done through use of a scanner.
The simplest object movie consists of a sequence of images of the object acquired by photographing the object from different viewpoints encircling it. Equivalently, the same sequence of images can be photographed from a fixed viewpoint, but with the object in different orientations. For example, the object could be rotating on a turntable. The latter is a more common acquisition method.
Once acquired (and digitized, if necessary) and downloaded to a computer, the images comprising an object movie can then be displayed in sequence on a computer monitor in response to user input commands, in such a way that it appears that the user is manipulating the object.
During image acquisition, the tilt (i.e., elevation angle) of the physical or computer-simulated camera need not be horizontal with respect to the ground plane on which the object is resting, nor need it be constant. Several rotating sequences of photographs of an object taken with the camera at different tilt angles can be combined to provide the user with an experience of being able to rotate and tilt the object, thus providing an extra degree of freedom.
It is not necessary that the images reside on the user's computer. In fact, current client/server Internet applications operate by storing the images on a server computer, and allowing a user to interactively view the object movie on a client computer. The server computer sends to the client computer via the Internet whatever data is necessary for the client computer to be able to display the image requested by the user, in response to interactive user commands.
Systems for interactive viewing of object movies over the Internet are described in co-pending U.S. patent applications: Ser. No. 08/788,830, filed Jan. 6, 1997 and entitled METHOD AND SYSTEMS FOR SCALABLE REPRESENTATION OF MULTIMEDIA DATA FOR PROGRESSIVE ASYNCHRONOUS TRANSMISSION; Ser. No. 08/813,181, filed Mar. 7, 1997 and entitled METHOD AND SYSTEM FOR ENCODING MOVIES, PANORAMAS AND LARGE IMAGES FOR ON-LINE INTERACTIVE VIEWING AND GAZING; and Ser. No. 08/850,690, filed May 2, 1997 and entitled A METHOD AND SYSTEM FOR PROVIDING ON-LINE INTERACTIVITY OVER A SERVER-CLIENT NETWORK. The contents of the patent applications referred to in this paragraph are all hereby incorporated by reference.
SUMMARY OF THE INVENTION
When an object movie producer acquires a sequence of images of a three-dimensional object, a difficulty arises in ensuring that the images are well centered. Centering involves careful orientation of the object or the camera as the various snapshots are taken, which can be hard to achieve. Often the producer cannot preview the final object movie during image acquisition, and has minimal feedback during acquisition for re-adjusting or fine-tuning the placement of the object or the position of the camera. Although each individual snapshot can typically be previewed, the relative alignment of the snapshots to one another may not be previewable, and is hard to control.
Moreover, the physical configuration and mass distribution of the object can prevent it from being oriented as desired, in which case the producer is prevented from positioning the object in its desired placement.
The present invention provides an efficient image-based method for re-rendering of a sequence of images which were acquired during production of an object movie, so as to enable the producer to center the images. The invention is particularly useful as it does not require the producer to re-acquire the sequence of images, nor does it require sophisticated three-dimensional modeling. Moreover, it is implementable in a way that carries out the re-rendering very quickly, in real time or near real time on today's standard computer processors.
In one embodiment of the present invention, the re-rendering involves translating and magnifying the images so as to center them about a desired axis. Translating involves shifting the pixel values of the image horizontally and vertically. Since the object typically has a simple background, the area where the translated or shifted image leaves the bounds of the original image can be filled in with background color values. Magnification involves zooming in or out of the image, according to a scale factor. Zooming in to a specified image is accomplished by enlarging a desired sub-portion of the specified image to the size of the specified image. Zooming out of a specified image is accomplished by reducing a larger image that contains the specified image to the size of the specified image. Again, the part of the larger image that lies outside the specified image can be filled in with background color values.
In an alternate embodiment of the present invention re-rendering can also involve modifications to the images of types other than translation and magnification, such as warping and projection.
In addition some of the images in the sequence can be discarded, if they cannot be centered together with the others.
There is thus provided in accordance with a preferred embodiment of the present invention a method for centering a plurality of images which are snapshots of an object seen at a plurality of orientations, the method including computing modification parameters for the images, and modifying the images based upon the modification parameters using a computer.
Additionally in accordance with a preferred embodiment of the present invention the plurality of images are snapshots photographed by a camera from a plurality of viewpoints which encircle the object.
Moreover in accordance with a preferred embodiment of the present invention the plurality of images are snapshots photographed by a camera from a fixed viewpoint, with the object rotated at a plurality of angles of rotation.
Further in accordance with a preferred embodiment of the present invention the object is situated upon a turntable during image acquisition, the turntable being mounted upon an axle about which it is rotated at a plurality of angles, thereby effecting rotation of the object at a plurality of angles of rotation.
Still further in accordance with a preferred embodiment of the present invention the plurality of images are snapshots generated by a computer which simulates a camera.
Additionally in accordance with a preferred embodiment of the present invention the plurality of orientations are plural positions of the object as it is rotated about an axis of rotation.
Moreover in accordance with a preferred embodiment of the present invention the step of computing modification parameters is based upon position information for the axis of rotation.
Further in accordance with a preferred embodiment of the present invention the step of computing modification parameters is based upon angle information for the plurality of orientations.
Still further in accordance with a preferred embodiment of the present invention the step of computing modification parameters is based upon a tilt angle of the camera.
Additionally in accordance with a preferred embodiment of the present invention the tilt angle of the camera is manually specified by a user by means of a user interface.
Further in accordance with a preferred embodiment of the present invention the tilt angle of the camera is
Blakely & Sokoloff, Taylor & Zafman
MGI Software Corporation
Vo Cliff N.
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