Krzysztof Wandachowicz

Using BRDF for radiance and luminance calculation

Abstract Correct representation of the phenomenon of reflection of visible radiation or thermal radiation is a necessary precondition for accurate modelling of luminous phenomena (visualization) and thermal phenomena (heat transfer). A full description of reflective properties of materials is included in BRDF 1 —difficult to apply in computer calculations. The article presents several BRDF models and for the most extended model (the one developed by Embrechts), a method of determination of optimum coefficients defining BRDF is proposed, based on empirical data. The article presents an example of visualization illustrating the effects of spread reflection, using the method presented.

Reflector shape design using merit function and genetic algorithm

The article presents results of research on the calculation of the shape of a mirror reflector that has not a rotating symmetry. The objective function ensures the highest possible average value of illuminance and uniformity ratio of illuminance. Optimization calculations were carried out for different light source dimensions with the use of merit function. In this paper two strategies that help to get global optimum are compared. First of them is starting ten times from ten different points and find the best solution. The second is using strategy of alteration of population diversity that is executed in one, programmed process.