Part of a lighting designers craftsis to imagine the appearance of ansilluminated area before it is built.sExperienced designers, however, cansbe surprised once construction begins.sNew uses of construction materials,snew techniques and experimentationsoften lead to profitable discoveries asswell as occasional mistakes. Designsexploration is to be encouraged, asslong as it does not conflict with a clientsspreference. Unfortunately, a clientsmay insist on an unwise choice,sresulting in confrontation and potentialsdissatisfaction. For these reasonssand others, designers and their clientssfrequently prefer to previewsmany decisions before they are made.

Computers offer the ability to predictsvariables in design including appearance, thereby making designersand client education more economical.sBy simulating the behavior ofslight, computers can predict luminancesand illuminance levels, andsmake synthetic images of a space beforesit is built. In lighting design, ascommon practice is to begin with astarget illuminance distribution, thensuse manufacturers tables and simplescalculations to arrive at an initialslighting arrangement. For criticalsareas, flexibility is built into the systemsso that the light distribution cansbe tuned during installation. This approachsworks well in most applications,sbut when daylighting is a keysfeature, or aesthetics are stressedsover illumination levels, it becomessmuch more difficult for the designersto be convinced, and even harder tosconvince the client of a quality design.sIn this situation computer prediction of appearance would be invaluable.