VII.7 – DARKLIGHTS

Publisher Summary This chapter presents an overview of darklights. Every image designer knows that appropriate illumination is an important part of an effective image. The play of light on the surfaces of the scene gives the image depth and mood, indicates position and character, reveals both objective visual information, and suggests subjective emotional impressions. Even objective physical rendering, when used in fields such as scientific visualization, requires sensitive judgement for the placement and control of illumination. The chapter discusses a tool that is used subconsciously by many painters and quite explicitly by many graphics designers. Darklights can cause the final pixel values to dip below zero. The techniques that are applied to map pixel values greater than one into gamut should also be applied to pixel values that dip below zero. As with all lights, darklights must be designed and positioned with care to achieve an effect. They are useful for simulating fuzzy shadows, darkening up corners of rooms, and changing the relative brightness of objects without affecting the basic lighting scheme. They are naturally available in virtually all rendering systems. If used with care and sensitivity, darklights can extend one's expressive power with the medium of image synthesis.