This is so for a number of reasons. Calculation and display of results by conventional programs may not be adequate for the range of numbers encountered in obtrusive light compliance. For example, a calculation grid may be required which represents the wall of a dwelling which is at some odd angle to the coordinate system being used in the design. Many conventional design programs do not have this ability. For example, a grid representing a window may need Vertical Illuminance and Intensity from each luminaire to be calculated.
Some application programs handle only one parameter per run.
Using conventional programs for both the application and obtrusive parameters becomes tedious as factors need to be included then excluded depending on the current parameter being calculated. Application design less frequently requires obstructions to be considered, hence not all programs have this capability. Application design is usually evaluated over an area with average, minimum, and maximum values being used to assess compliance with design objectives. Isolines, shaded diagrams, etc. are often used to evaluate the pattern to facilitate design adjustments. Obtrusive and upward light parameters are maximum limits which must not be exceeded, even at a single point.