Contemporary goals for interior lighting calculations put severe demands on traditional calculative techniques. Those goals include a knowledge of not only the local density of incident luminous flux (illuminance of "footcandles level") but also a compete knowldege of the direction from which the flux comes as it arrives at any point in the space. This latter requirement has two sources: (1) the need to calculate contrasts and luminances of visual work, both quantities being sensitive to the spatial distribution of incident flux, and (2) the desire to have an accurate luminance map (even a synthetic photograph) of the space for purposes of qualitative, aesthetic, and psychological appraisal. Recent advances in the computational techniques used for interior lighting calucations make it possible to meet the requirement for information discussed above using only an advanced programmable calculator or any of the currently available 16-bit microcomputers.