The present invention relates to transmitter-receiver of three-dimensional skeleton structure motions and its method, which efficiently transmits/receives natural motions of a character having a complex skeleton structure, e.g., human beings, when producing or commercially utilizing three dimensional computer graphics (3DCG) based on network, e.g., internet.
As a 3DCG application, virtual malls on internet, e.g., WWW (world wide web) and various homepages have been noticeable. Particularly, the rapid developments of internet helps to improve the circumstances in which 3DCG of such as games and movies are readily handled at home.
In a conventional WWW, a machine called xe2x80x9cserver,xe2x80x9d such as a personal computer (PC) and workstation, is connected, through internet, to a plurality of machines called xe2x80x9cclient,xe2x80x9d such as PC. In response to the demand of a client, as required, data including information on picture image, voice, text and layout provided by a server is downloaded, and then reconstructed at the client side to obtain necessary information. In such communication between servers and clients, there is utilized a communication procedure based on TCP/IP (transmission control protocol/internet protocol).
Conventional data provided by servers were mainly text data and picture image data. Recently, the standardization of VRML (virtual reality modeling language) and the browser of the VRML advanced, and the modern trend is toward the transfer of 3DCG data itself, such as shapes and scenes.
Brief description will be given of the VRML. To transfer picture data, particularly moving picture data using a conventional data format mainly for picture image and text, e.g., HMTL (hyper text markup language), requires much transfer time and costs. Therefore, network traffic restriction is imposed on the present-day system. In a conventional 3DCG, shape, viewpoint and lighting information were all processed by three-dimensional data. As computer graphics (CG) technology is advanced, the image quality of picture image created by CG is rapidly improved. In view of data quantity, it is more efficient to transfer CG data as it is. In this case, data compression ratio is normally not less than 1/100 of the transfer of the equivalent picture image data. Therefore, the modern trend is toward the standardization of the transfer method of 3DCG data through network. As an attempt, the standardization of 3DCG data called xe2x80x9cVRMLxe2x80x9d has been proposed (VRML Ver. 2.0). The VRML Ver. 2.0 defines, for example, shape data called xe2x80x9cprimitive,xe2x80x9d data format of various lighting source data, viewpoint data and texture data, and the designation process of rigid body motion.
Among the conventional CG field, animation that produces picture image in real-time, i.e., so-called real animation, is worthy of remark. The reproduction of the real motion of CG characters utilizing a real animation, is being studied mainly in the field of CM (commercial message) and movies. There are for example a method called xe2x80x9ckinematics methodxe2x80x9d in which a complex shape such as human being is represented by a skeleton structure (hierarchical structure), and its complex motion is reproduced naturally by the definitions of the motion quantity of the joints of skeletons that change from time to time.
The aforementioned kinematics method was primarily developed in the field of robotics engineering. This method is to decide the posture of a skeleton model having a linear link structure comprising links and joints, by setting the angle of rotations in the directions of X, Y and Z axes of the joint parts of the skeleton model, and the motion quantity (position) in the directions of X, Y and Z axes.
By utilizing the kinematics method in a character of an arbitrary skeleton structure created by CG, it is being able to decrease the data quantity and reproduce natural motions of such as human being and dinosaurs, compared to a conventional polygon based animation that is created by the simultaneous use of key frame method and the like.
In 3DCG modeling language on a conventional internet in which VRML plays a central role, however, it is present condition that no consideration is given to methods for defining continuous time series motions of objects, and that there is no method for defining the motions of complex shapes of human being and the like, i.e., natural postures of hands and feet.
In a conventional animation creation based on kinematics method, the creation of smooth motions requires much motion data. In terms of applications to network, traffic issue is left unsettled.
It is an object of the present invention to realize that between clients and servers being connected on internet, complex shapes (avatar) of such as human being having a skeleton structure (hierarchical structure) and motion data serving as the base of the avatar are transmitted/received, and the avatar is then interactively operated with each other in three-dimensional virtual space on network.
Other objects and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific embodiment are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to the those skilled in the art from this detailed description.
The present inventors have found out that the above objects can be attained-by the following facilities:
(i) a mechanism for defining a complex structure of such as human being by a skeleton structure, compressing, restoring and transmitting/receiving the reference position (hereinafter referred to as xe2x80x9crootxe2x80x9d) of a specified skeleton and the motion information of each joint position of the skeleton;
(ii) a mechanism for disassembling the motion data of the skeleton structure to be added to an initial information, which comprises the hierarchical relationship of the skeleton structure, the initial state of the skeleton structure, constraint of the skeleton structure (e.g., the degree of freedom of each joint rotation and the rotation range), shape data to be attached to skeletons and data relative to the attachment to the skeleton structure, into the representative element data of the motions in three-dimensional virtual space (hereinafter referred to as xe2x80x9cbasic motionxe2x80x9d), transmitting/restoring the disassembled basic motions together with methods for connecting the representative motions of the basic motions;
(iii) a mechanism for deciding the postures of necessary skeleton structures based on the transmitted/received animation information; and
(iv) a mechanism for interactively altering, for example, the operations of motions such as the directions of motions and the stream of the basic motions, according to the instructions of users who operate based on the motions of avatars to be transmitted/received.
In accordance with this finding, in transmitting/receiving three-dimensional motions of a character having a complex structure such as human being, it is possible to define a human hierarchy by a skeleton structure and then transmit/receive, in time series, the motion quantity of some joints of the defined skeleton structure in three-dimensional virtual space. It is also possible to add, into representative motion elements, connection methods thereto, and then transmit/receive it. These enable to transmit/receive natural and smooth motions of characters in transmission/receiving system based on network, thereby considerably reducing the data quantity during the transfer.