Computer reconstruction of 2-D photographs from alternative viewpoints

The reconstruction of 'mug-shots' from various angles has obvious advantages where witnesses are attempting to identify a subject who may have been observed from a viewpoint other than that recorded on a frontal photograph. Alternatively, the ability to modify a frontal photograph in such a way that it allows reconciliation of the photograph and views of the subject as seen by witnesses from different viewpoints, has the potential to lead to a more accurate description of the subject being obtained. Both of these applications are facilitated by a computer graphics technique described in the paper, in which an image, held in computer memory, of a frontal facial photograph, is texture mapped onto the surface of an underlying 3-D skeletal model. To reconstruct the photograph to show the view from a different position, first the model, stored in the computer as a list of polygon edges and vertices, is rotated, translated and scaled by an appropriate amount. Then each pixel of the original frontal view of the subject is remapped with reference to the model, to derive the new view. In addition to allowing the reconstruction of photographs from various viewpoints, the technique permits alterations to be made to the appearance of reconstruction by blending in picture fragments such as mouth and eye sub-images and allows computer generated lighting effects to be added.