1. Apparatus for computing a three dimensional model of an object, comprising: at least one directional energy source arranged to directionally illuminate the object; an imaging sensing assembly having at least two spatially separated viewpoints at fixed positions relative to each other, the imaging sensing assembly arranged to record a series of images of the object at each viewpoint when the object is illuminated by the source; at least one localisation template having predetermined geometrical features, the localisation template arranged in use to be visible to at least one of the viewpoints simultaneously with the object; and a processor arranged to analyse the images recorded at the viewpoints, so as to: determine the location and pose of each viewpoint relative to the template for each image in the series of images; generate photometric data for the object using the calculated location and pose of the viewpoints and the direction of illumination from the energy source; generate geometric data comprising an initial three dimensional model of the object by performing stereoscopic reconstruction using optical triangulation; and combine the geometric data and photometric data to construct the three dimensional model.