Generating an image of a three-dimensional object

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS FIG.
13 shows an alternative co-ordinate system.
The purpose of the system to be described is to generate a synthetic two-dimensional display of a head, so that the image seen in the display appears as seen from any desired viewpoint, or a sequence of such images so as to provide animation.
The system is based on a so-called wire frame model, which is adapted to resemble a particular real--or imaginary--person.
To give an overview, this is achieved by: (A) the provision of a standard or generic wire frame model having a set of points defining the vertices of polygonal facets of the model which has a basic default shape; (B) changing this shape to match the shape of the person to be represented; (C) defining the appearance of the individual facets by reference to a "texture map" containing two-dimensional information as to the appearance of the person when viewed from each of a number of fixed directions; (D) using the "customised" head definition thus created to generate, in response to control information specifying a desired viewpoint or--for animation--a sequence of such viewpoints, a signal for supply to a display device.
If desired, such animation may include animation of the mouth to accompany the generation of synthetic speech, for example using a text-to-speech synthesiser and providing sequences of mouth shapes ("visemes") along with the phonemes of the speech.
Steps (A), (B) and (D) are conventional, and the major part of the following description will, therefore be devoted to the details of Step (C).
FIG.
1 shows a suitable apparatus which has a store 1 for containing all the data defining the head.
A first processing device 2 has access to the store 1 and also to a second store 3 containing programs for operating the processing device 2 so as to perform steps A, B and C.
A second processing device 4, with its own program store 5, serves to perform step (D), providing at an output 6 digitally coded images, or a video signal, for driving, directly or after storage and/or transmission, a visual display device (not shown)