An apparatus and method for computing a three dimensional model of a surface of an object are disclosed. At least one directional energy source (106-109) directionally illuminates the object (101). An imaging assembly (104), having at least two spatially separated viewpoints (111,112) at fixed positions relative to each other, records a series of images of the object at each viewpoint when the object is illuminated by the source. At least one localisation template (102,103) having predetermined geometrical features is visible to at least one of the viewpoints simultaneously with the object. The images recorded at the viewpoints are analysed so as to determine the location and pose of each viewpoint relative to the template for each image in the series of images. Photometric data for the object is generated using the calculated location and pose of the viewpoints and the image data. Geometric data comprising an initial three dimensional model of the object is generated by performing stereoscopic reconstruction using optical triangulation. The geometric data and photometric data are then combined to construct the three dimensional model.