Computer graphics applications usually treat appearance in different ways, depending on whether they start from scratch, from 3D scenes or from videos. I argue that a common model of appearance would better serve such applications: it would greatly help the creation of complex appearance patterns in drawing applications; it would permit to connect physical descriptions to appearance percepts in rendering; and it would give a rich basis for image analysis at the compositing stage. Such a model should describe appearance in a perceptually plausible manner, directly identifying invariants across different lighting or motion conditions. This requires to draw connections with Human Vision; but there is also potentially room for graphics to inspire new perceptual investigations.