Measurement and modeling of simplified trees for daylighting computer simulation

Abstract Predicting the effect of arboreal vegetation on daylight performance is a complex and difficult task as it depends on accurately simulating the passage of light through its canopy. Variables such as leaf size, shape, reflectance and transparency, among others, should be considered. Thus, modeling a tree exactly simulating the real situation is impractical, not only because of the quantity and complexity of the variables, but also because of the overload of the model. In this context, the main aims of this research are: to improve the way of measuring the permeability of arboreal vegetation to daylight, which we call the "canopy gap fraction", using hemispherical photography and image analysis; and apply these measurements in simplified three-dimensional digital models to use in computational daylight simulations. Three digital models, namely "blinds", "translucent", and "gaps" were developed, simulating four tree species. The actual and simulated light levels of each one were compared and validated according to the relative MBE and RMSE indicators. The "gap" tree model, for example, was especially suitable for the Pitombeira and Carolina tree species, with relative MBE values of 0.21 and -0.12, as well as relative RMSE values of 0.02 and 0.03, respectively, proving the relevance of the developed method.