Figure 3. (a) Orientation consistency in the presence of transparency and indirect illumination effects. The reference sphere and the objecthave different material properties but they act like ideal specular objects when they reflect specular highlights (brightness and contrastwere enhanced for visualization). (b) Under the orthographic camera assumption, we can directly obtain the normal orientation from thereference sphere. Notice that given a single view, only a subset of normals can be computed. (L is light direction, R reflection direction,N is normal direction.)