Abstract: Described are computer implemented methods and systems for generating an image of a person wearing a selectable piece of apparel by accounting for the illumination condition data present in a photo of the person. The method comprises the steps of providing as inputs to a computing device a 3D person model of at least a part of the person, a photo of the person corresponding to the 3D person model, and illumination condition data relating to the photo. The method also comprises selecting a piece of apparel and generating the image as a combination of the photo and a rendered 3D apparel model of the selected piece of apparel, wherein rendering the 3D apparel model considers the illumination condition data and the 3D person model.