Abstract:
A communications system is described in which a plurality of mobile phones are provided, each including means for generating a user interface for enabling users to identify points in images as feature points. All of the phones are then operable to utilise points identified by users to generate 3D models of individuals in the images. The 3D models are generated by associating stored average depth data for points corresponding to the co-ordinates of the feature points and further points whose position is identified relative to the co-ordinates of the feature points. The 3D models are then used to generate images which are displayed on the mobile phones.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present application relates to methods and apparatus for generating models of individuals. In particular, embodiments of the present application relates to methods and apparatus for modelling individuals for display on mobile phones. 
   2. Description of the Related Art 
   There are many applications for computer systems that are able to generate recognisable images of individuals. These applications range from systems for displaying the face of a caller on a telephone through to computer graphics generated within computer games. One known method of modelling human faces is using principle component analysis, an example of which is disclosed in ‘Active Appearance Models’ Cooks et. al., Proc. European Conference of Computer Vision 1998, Vol 1.2, pp. 484–498, Springer, 1998. 
   SUMMARY OF THE INVENTION 
   In order to generate a model of the way in which faces vary, a large data set of different faces is first obtained. Feature points on the faces are then identified so that an average face can be determined. The manner in which each individual face used to generate the model varies from this average face can then be calculated and the results subjected to principle component analysis to determine the most significant ways in which faces within the data set vary. 
   By generating a model of an individual face using a limited number of the most significant variations, a reasonable approximation of a specific individual face then can be generated. 
   When displaying a 3D face model, it is desirable to be able to animate the eyes of such models. However, where models of faces vary in size, it is difficult to generate an animatable model of a 3 dimensional eye ball which is correctly sized to fit into a 3 dimensional face model such as may be generated utilising principle component analysis. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further aspects of the present invention will become apparent with reference to the accompanying drawings in which: 
       FIG. 1  is a schematic block diagram of a communications network including a pair of mobile phones in accordance with a first embodiment of the present invention; 
       FIG. 2  is a schematic block diagram of a mobile phone of  FIG. 1 ; 
       FIG. 3  is a flow diagram of an overview of the processing of data by the mobile phone of  FIG. 2 ; 
       FIG. 4  is a flow diagram of the processing of data by a mobile phone of  FIG. 2  to generate a set of Eigen values and eye data; 
       FIG. 5  is an exemplary image of an eye for explaining the generation of eye data; 
       FIG. 6  is an exemplary illustration of eye data generated from the image of  FIG. 5 ; and 
       FIG. 7  is a flow diagram of the processing of data by a mobile phone of  FIG. 2  to generate an animatable image of a caller. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   First Embodiment 
     FIG. 1  is a schematic block diagram of a communications network system. The communications system comprises a plurality of mobile phones  1 - 1 – 1 -N that are connected to each other via a communications network  5 . In accordance with this embodiment of the present invention, each of the mobile phones  1 - 1 ;  1 -N is adapted to enable images generated from a 3D model of a caller to be displayed and comprises a camera  7  for taking pictures of the user of the phone  1 - 1 ;  1 -N; a screen  9  for displaying images of the face of an individual calling the mobile phone  1 - 1 ;  1 -N generated from a 3D model of the caller, a keyboard  11 , a loudspeaker  13  and a microphone  14 . 
   As will be described in detail later, the mobile phones  1 - 1 – 1 -N in accordance with this embodiment of the present invention are each adapted to generate animatable three dimensional models of users from images taken with the cameras of the phones  1 - 1 – 1 -N. The generated models are then transmitted via the communications network  5  when a telephone call is made. Upon receipt of a model, the mobile phones  1 - 1 – 1 -N utilises the received model co-ordinates to generate an animated three dimensional representation of the individual making the call in which the eyes of the caller are made to move. 
   The structure of mobile phones  1 - 1 – 1 -N in accordance with this embodiment of the present invention will now be described in greater detail with reference to  FIG. 2 . 
     FIG. 2  is a schematic block diagram of a mobile phone  1  for use in accordance with this embodiment of the present invention. 
   In this embodiment, each of the mobile phones  1 - 1 – 1 -N comprises a processing unit  25  which is connected to the keyboard  11 , the camera  7 , the screen  9 , the loudspeaker  13  and microphone  14  of the phone  1 . In addition the processing unit  25  is also connected to a transmitter/receiver  27  and a modelling unit  28 . 
   In this embodiment, the modelling unit  28  has stored within it a model generation module  30  for determining Eigen values for principle component analysis models together with eye data for animating the models eyes; an image generation module  32  for processing received Eigen values and eye data received from other phones  1 , to generate a three dimensional animated image of a caller on the screen  9 ; and a data storage section  35  for storing images and calculated Eigen values and eye data. 
   The processing of data by the processing unit  25  and modelling unit  28  of a mobile phone  1 - 1 ;  1 -N in accordance with this embodiment of the present invention will now be described in detail with reference to  FIG. 3 . 
   The processing unit  25  initially (s 3 - 1 ) determines whether any data has been input via the keyboard  11  indicating that the user of the phone  1  wishes to generate a new face model for storage within the memory  28  of the phone  1 . 
   If this is the case, the processing unit  25  then (s 3 - 2 ) causes a prompt to appear on the screen  9  of the phone  1  requesting the user to take a photograph of themselves using the camera  7  of the phone  1 . 
   When an image obtained using the camera  7  the image is processed by the model generation module  30  of the modelling unit  28  to determine a set of Eigen values and eye data for generating an animatable model of an individual (s 3 - 3 ) as will now be described in detail with reference to  FIGS. 4 ,  5 , and  6 . 
     FIG. 4  is a flow diagram of the processing of the model generation module  30  for determining Eigen values for a principle component analysis model of an individual and eye data for animating that model. Initially (s 4 - 1 ) the image data obtained using the camera  7  is processed by the model generation module  30  of the modelling unit  28  in a conventional manner to determine a set of Eigen values representing weighting values for principle component analysis vectors for generating a three dimensional wire mesh model of the individual appearing in the image obtained using the camera  7  and texture render data for texture rendering the generated wire mesh model. 
   After a set of Eigen values for creating a representation of an individual appearing in the image have been stored, the model generation module  30  then (s 4 - 2 ) identifies the location of the eyes of the individual appearing in the image obtained using the camera  7  of the phone  1 . The location of the eyes in the image of the individual may be identified using any conventional feature recognition techniques or alternatively may be identified by a user entering data into the phone  1  via the keyboard  11 . 
   The model generation module  30  of the modelling unit  28  then (s 4 - 3 ) identifies the positioning of the pupil  100  in the eyes appearing in the image and determines for each eye the distance D between the pupil  100  and the caruncle  102  at the corner of the eye. This distance is indicative of the extent to which the sclera or white of that eye is visible in the image. 
   When the model generation module  30  has determined a measurement D for both of the eyes in the image, the model generation module  30  then selects for further processing the portion of the image corresponding to the eye in which the distance D between the pupil  100  and the caruncle  102  is greatest. 
   When the model generation module  30  has determined which of the eyes reveals the greatest extent of sclera, the model generation unit  30  then calculates eye data for animating the eye. This is achieved by initially copying the pixel data for a window of pixels extending from the pupil  100  to the edge of the caruncle  102 . In this embodiment this window extends between the pupil  100  and the caruncle  102  and has a height of three pixels. The portion of the image data copied as eye data is shown highlighted in  FIGS. 5 and 6 . 
   The model generation module  30  then calculates eye data for the remainder of the eye utilising this pixel data extracted from the image. In this embodiment this is achieved by taking advantage of the rotational symmetry of the appearance of an eye ball. For each of the pixels in a texture map as illustrated in  FIG. 6 , other than those corresponding to the pixels copied over from the window between the pupil  100  and the caruncle  102  from the image data, the model generation module  30  determines the distance of the pixel from the pixel representing the centre of the iris. The model generation module  30  then selects from the pixels in the window in between the pupil  100  and the caruncle  102  a random pixel of the three pixels at that distance from the centre of the iris  100 . This pixel is then copied over as eye data for the position of the eye. By making a selection of one of the three pixels from the window at a certain distance from the pupil  100  the basic rotational symmetry of an eye ball is modelled whilst avoiding generating eye data that has perfect rotational symmetry. 
   Returning to  FIG. 3  after an image has been processed to determine a set of Eigen values and eye data for modelling an individual appearing in the image, the Eigen values and eye data are stored (s 3 - 4 ) in the data storage section  35  of the modelling unit  28  for later retrieval. 
   If the processing unit  26  determines (s 3 - 1 ) that a request for generating a new face model has not been entered, the processing unit  25  then (S 3 - 5 ) determines whether a telephone number has been entered using the keyboard  11 . If this is the case, the mobile phone then connects to the phone  1 - 1 ; 1 -N identified by the telephone number via the communications network  5  in a conventional manner. The mobile phone  1  then transmits (S 3 - 6 ) via the communication network  5  Eigen values and eye data stored in data storage section  35  of the modelling unit  28 . 
   The processing unit  25  then waits (s 3 - 7 ) until a reply is received from the telephone being called via the communication network  5  and the transmitter/receiver  27 . When a reply is received the reply will include Eigen values and eye data from the telephone being called. The processing unit  25  then passes the Eigen values and eye data and to the image generation module  32  of the modelling unit  28 . The image generation module  32  processes the received data to generate (s 3 - 8 ) an image of the receiver of the call which is displayed on the screen  9 . 
   Specifically, the image generation module  32  processes the Eigen values and eye data to generate an animated three dimensional model of the caller as will now be described in detail with reference to  FIG. 7  which is a flow diagram of the processing of the image generation module  32 . 
   Initially (s 7 - 1 ) the image generation module  32  receives the Eigen value and eye data from the processing unit  25 . The image generation module  32  then (s 7 - 2 ) generates a wire mesh model representation of a corner and a texture map for texture rendering the generated wire mesh model utilising the Eigen values and a principle component analysis modelling system in a conventional manner. This data is then utilised to generate an image of the individual on the screen  9  of the mobile phone  1 . 
   In order to animate the eyes of the generated image the image generation module  32  then determines which of the triangles of the generated wire mesh model are representative of the individuals eyes. From the manner in which a principle component analysis model representation of an individual is built up, these triangles will be the same triangles for all representations generated using a particular principle component analysis model. 
   The image generation module  32  then (s 7 - 3 ) resets the texture co-ordinates for texture rendering the triangles representing the eyes in the model to identify those triangles to be texture rendered utilising the eye data received from the processing unit  25 . The portion of the image representing the eyes is then re-rendered utilising the identified texture from the new texture co-ordinates. 
   The image generation module  32  then (S 7 - 4 ) determines whether the call being made is completed. If this is not the case the texture co-ordinates for the triangles being rendered utilising the eye data are slightly amended so as to be offset from their current positions by a predetermined direction. The triangles representing the eyes in the image are then re-rendered (s 7 - 3 ) utilising these new texture co-ordinates. The effect of changing the portion of the eye data utilised to texture render individual triangles representing eyes in an image gives rise to the impression that the eyes themselves are moving and therefore animates the image which is generated and displayed on the screen  9  of the phone  1 . 
   Returning to  FIG. 3 , once an image of a caller has been calculated and displayed (s 3 - 8 ) on the screen  9  of the phone  1 , the phone  1  then proceeds (s 3 - 9 ) to transmit audio data received via the microphone  14  and output received audio data received via the transmitter/receiver  27  out through the loudspeaker  13  in a conventional manner whilst continually re-rendering the texture data for representing the eyes of a displayed image to cause the eyes of the image to appear to be animated. 
   If the processing unit  25  determines (s 3 - 5 ) that no call has been made using the keyboard  11 , the processing unit  25  then determines (S 3 - 10 ) whether a call has been received by the transmitter/receiver  27 . If this is not the case the processing unit  25  then once again checks (s 3 - 1 ) whether data indicating that a new face is to be stored has been input via the keyboard  11 . 
   If the processing unit determines (s 3 - 10 ) that a call has been received via the transmitter/receiver  27 , the data received will include Eigen values and eye data. The processing unit  25  then (s 3 - 11 ) stores the received image data by passing this data to the data storage section  35  of the modelling unit  28 . 
   The processing unit  25  (s 3 - 12 ) then causes the Eigen values and eye data previously generated by a user and stored within the data storage section  35  of the modelling unit  28  of the phone  1  to be dispatched via the transmitter/receiver  27  and the communications network  5  to the phone  1  from which a call has been received. The processing unit  25  then causes the image generation module  34  to generate (s 3 - 8 ) and animate an image of the caller using the Eigen values and eye data received from the communications network  5  as has previously been described. 
   Finally after an image has been displayed, the processing unit  25  causes audio data received by the microphone  14  to be transmitted via the transmitter/receiver  27  and audio data received by the transmitter/receiver  27  to be output by the loudspeaker  13  in a conventional manner, whilst the eyes of displayed images are animated (s 3 - 9 ), in the same manner as has previously been described. 
   Further Embodiments and Modifications 
   Although in the above embodiment, a system has been described in which eye data for animating a model is generated from the same image utilised to create the model, it is possible for the same animation effect to be realised utilising a pre-stored set of eye data. Such an alternative system is not a preferred embodiment of the present invention as it has been determined that the appearance in colour of individuals irises and scleras can vary significantly depending upon the lighting conditions in which an image of an individual is taken. An advantage of using the technique described with reference to the drawings is that the colour of the eye data generated using these techniques matches the rest of the model of that individual being generated. 
   Although the above embodiment has been described in relation to a system in which processing takes place on mobile phones and the images generated are images of callers to those mobile phones, it will be appreciated that the present invention has wider applications for animating the eyes of any computer representation of an individual generated from texture rendering a wire mesh computer representation of the an individual. 
   Although the embodiment or the invention described with reference to the drawings comprises computer apparatus and processes performed in computer apparatus, the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source or object code or in any other form suitable for use in the implementation of the processes according to the invention. The carrier be any entity or device capable of carrying the program. 
   For example, the carrier may comprise a storage medium, such as a ROM, for example a CD ROM or a semiconductor ROM, or a magnetic recording medium, for example a floppy disc or hard disk. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or other means. 
   When a program is embodied in a signal which may be conveyed directly by a cable or other device or means, the carrier may be constituted by such cable or other device or means. 
   Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes. 
   Although in the above embodiments, systems for modelling faces have been described, it will be appreciated that the present invention is more generally applicable. Specifically, the present invention may be utilised to model for example whole heads rather than only faces or alternatively larger portions of an individual (e.g. head and shoulders) or even for generating full body models. 
   Further, although the above embodiments have described systems in which principle component analysis models are utilised to generate representations of individuals, it will be appreciated that the present invention is applicable to other systems where models of individuals are generated. Thus for example the present invention is applicable to a system in which a 3-D model head of an individual is created by identifying the location of features of an individual in an image and associating those points with depth data for the average depth for those points on the surface on an individuals head. Representations of an individual could then be created and animated utilising eye data in the manner which has previously been described.