BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to computer systems. More particularly, the present invention relates to computer graphics and a graphical image display system that use a visual server to generate and transmit images to a client.

2. Description of the Related Art

Computer generated images are created in a series of several steps: modeling, or describing the objects in mathematical terms; animation, or describing how the objects move over time; and rendering, or determined which of the images defined by the modeling and animation programs are visible on the screen for every frame, assigning color to those images, and drawing them. Of these, rendering is the most difficult as it is the most processing intensive action. Because the generation of images is both processing and memory intensive, a client computer often relies upon other processors and memories, such as a server, to assist in generating the data to render new images. In the existing network model, storage and caching of content and applications can occur on a centralized server, but the actual software applications execute on a system in the client user space. The network thus allows the server to supply image processing resources beyond the constraints of a remote terminal, while taking advantage of client resources for certain tasks. Several existing systems utilize the client-server model to process and render images at a client display with the assistance of server resources.

In methods of client-server graphics that employ image transmission, the server unit requires a relatively high bandwidth connection even if real-time image compression and decompression is employed. Even in geometric replication methods, such as VRML, which generally have a lower bandwidth requirement, the image processing does not decrease the storage or processing requirements of the client. In these systems, the client must be capable of 30 rendering the complete replicated database in real time, and the server does not provide true image generation services. Rather, the server functions primarily as a database server. For example, in a client-server method based on a hybrid image transmission and geometry transmission approach, the server unit maintains a low level-of-detail database and a high level of detail database. For each frame of a real-time image stream, images are generated from both the low level-of-detail and high level-of-detail database. The difference between the two images is computed using known methods of image processing. The client unit contains only a low level-of-detail geometric database and renders this database for each frame, and the difference image computed on the sever is compressed and transmitted to the client in real-time which decompresses and composites it together with the image generated by the client from the low level-of-detail database. The result is a high level-of-detail, high quality image that requires a relatively low transmission bandwidth to transmit the relatively low information difference image. Such method also requires relatively limited client storage and processing capabilities. While this method can decrease the computational load of the client and reduce the communication costs, it requires both real-time image compression and decompression and further requires that special image compositing be added to the pipeline. In addition, the entire low level-of-detail database must be stored and processed by the client.

Another known method of client-server image processing is transmitting a transformed and compressed low level-of-detail representation of the geometric database in screen-space representation from the client to the server. The low level-of-detail geometric primitives are transmitted for every frame, and such action increases the required connection bandwidth. Only the primitives that are actually visible for each frame need to be transmitted in this approach. Moreover, since primitives visible in a current frame are likely to be visible in a subsequent frame, the repeated transmission of primitives that have been transformed to image-space representation is an inefficient use of available bandwidth. Any processing to identify repetitive primitives requires further client resources, which hampers the image displaying process.

A further approach to distributed client-server image generation is based on demand-driven geometry transmission to the client. In this method, the server determines and periodically updates a list of potentially visible primitives for each client using a spherical clipping volume around a viewpoint. The result is then compared to a list of primitives previously transmitted to the corresponding client and only those potentially visible primitives that have not been previously transmitted are sent to the client. However, this method reduces communication cost by limiting transmission to those primitives that have become potentially visible. The client replaces primitives in the client display list when they are no longer included in the spherical clipping volume, and thus, the storage and computing requirements of the client are limited to only those primitives in the potentially visible set. However, as this method uses a limited inclusion volume, a major disadvantage is that distant primitives can be arbitrarily excluded from the potentially visible data set. Further, the use of a spherical inclusion volume results in the inclusion and transmission of a large number of geometric primitives that are not visible in the current frame and are unlikely to be visible in upcoming frames, an example being primitives in the inclusion sphere behind the viewpoint. As a result, the demand-driven geometry transmission makes inefficient use of available transmission bandwidth and available client storage and computing resources, and the client resources are taxed because the client must compute removal of primitives by clipping to the inclusion volume, and implement display list replacement and compaction protocols.

Client graphic image display processing capabilities are even further taxed in the display of 3-dimensional images. In existing clients, the implementation of a system delivering 3D graphics requires graphics hardware at the client, which presents several problems. The additional hardware increases the cost of the client hardware as the graphics hardware must be incorporated and integrated therewith. Further, the software and hardware used to generate 3D images is in constant flux, and the system must be continually upgraded, creating an additional expense and a logistical burden for the client. Moreover, the remote hardware impedes the central maintenance and coordination of configurations of client software, which is an important capability and critical to the product viability of many applications.

Some clients use separate 3D hardware component to assist in processing the images, but with the constant change of graphics languages and protocols, the hardware becomes obsolete rather quickly, which adversely impacts the value of the client. Furthermore, the use of programmable graphics hardware within the client system is difficult because the client resources are inherently static and limited.

Therefore, for reasons of cost, size, and power consumption, sophisticated three dimensional graphics are not available on common consumer client devices such as personal digital assistants (PDAs) mobile telephones and set-top boxes used to decode cable and satellite television signals. Consequently, it would be advantageous to display complex three dimensional graphics, such as those used by games, on these consumer client devices.

Accordingly, it is to the provision of such an improved system and method of displaying images on a client consumer device utilizing the resources of a visual server that the present invention is primarily directed.

SUMMARY OF THE INVENTION

The present invention is an image display system and method of displaying images on a client through the use of the resources of a remote visual server. The Visual Server runs standard software, such as games, that are the same as versions running on standard personal computers. The Visual Server has certain support software modified to enable control of the application from the client and the delivery of the result of 3D drawing to the client. One or more clients can access the visual server, or an array of servers, wherein each of the clients includes an image display. The system includes a visual server having image data processing capabilities wherein the server selectively receives image-modifying data from one or more clients corresponding to a generated image, and the server generates a modified image based on the image-modifying data, and then transmits the modified image as compressed data back to the client.

The clients are in selective communication with the visual server, and each client selectively generates image-modifying data corresponding to the image resident on the image display of that specific client. The client selectively transmits the image-modifying data to the visual server, and the client then receives, as compressed data from the visual server, an image, or data representing an image, which is a modification of the previous image on the client altered in accord with the previously transmitted image-modifying data. The client includes the processing ability to uncompress the compressed image data from the visual server, and display the image defined by the decompressed data on the client image display.

The visual server and the one or more clients are in selective digital or analog communication preferably across a network, such as an Ethernet, WAN, LAN, or the Internet. Alternately, the visual server and one or more clients are in selective wireless communication, either point-to-point or relayed.

In generating the image-modifying data at the client and processing the image-modifying data at the visual server, the typical data processing segment is a frame. Alternately, the image-modifying data can be generated and transmitted from the client, and the modified image data sent from the visual server to the client after predetermined duration has elapsed.

The present invention further includes a method of displaying an image on a client in selective communication with a visual server wherein the method includes the steps of generating image-modifying data at the client wherein the image-modifying data corresponds to a generated image, transmitting the image-modifying data from the client to the visual server, receiving at the visual server image-modifying data from the client, generating at the visual server a modified image based upon the image-modifying data received from the client, transmitting the modified image from the visual server to the client as compressed data, receiving at the client as compressed data from the visual server an image modified by the transmitted image-modifying data, uncompressing the compressed image data at the client, and displaying the decompressed image on the client image display. The method alternately further includes the step of transmitting a link or other flag to the visual server from the client prior to the step of transmitting the image-modifying data from the client to the visual server in order to notify the visual server that image-modifying data is about to be transmitted from the client.

In the preferred embodiment, the steps of transmitting the image-modifying data from the client to the visual server and transmitting the modified image from the visual server to the client as compressed data are performed across a network, such as the Internet or other WAN, LAN, or Ethernet. Alternately, the steps of transmitting the image-modifying data from the client to the visual server and transmitting the modified image from the visual server to the client as compressed data are performed through wireless communication.

In one embodiment of the system, the step of transmitting the modified image from the visual server to the client as compressed data is transmitting the modified image from the visual server to the client as a compressed data comprising a frame, and accordingly, the step of transmitting the image-modifying data from the client to the visual server is transmitting the image-modifying data from the client to the visual server as data sufficient to generate an image frame. In another embodiment, the step of transmitting the modified image from the visual server to the client as compressed data is transmitting the modified image to the client after predetermined duration of generating an image based upon the transmitted image-modifying data has occurred, and accordingly, the step of transmitting the image-modifying data from the client to the visual server is transmitting the image-modifying data from the client to the visual server after a predetermined duration of generating image-modifying data.

The present invention therefore provides a commercial advantage in that the client can interactively generate complex graphical images to a user without the need for significant client resources. The system can be implemented with existing networking and communication technology between the client and the visual server, and the image data can be transmitted with known data compression protocols. Further, the visual server and its associated components are readily updateable and maintainable without having to directly access the individual client applications utilizing the image generating capabilities of the visual server.

Other objects, features, and advantages of the present invention will become apparent after review of the hereinafter set forth Brief Description of the Drawings, Detailed Description of the Invention, and the Claims.

