Light Interception and Leaf Shading

Light Interception Canopy architecture is modelled using a three dimenstional geometric approach. By knowing leaf orientation patterns and tracking solar position over the course of a day, ECOPHYS calculates the amount of radiation intercepted by individual leaves, accounting for solar angle and mutual leaf shading. The total intercepted radiation is then supplied to the photosynthesis submodel.

Shading

Shading is performed during each sunlit hour of the day. It is calculated for each leaf how much of the leaf area is sunlit and how much is shaded. ECOPHYS uses a bit-based dynamical canvas-building algorithm (Bit-DCBA) to calculate shading. The main steps of the algorithm are as follows:

1) Change coordiante system
2) Sort leaves by the z-values of the Leaf Center Point (LCP)
3) Build the canvas that each leaf will project on
4) Project leaves onto canvas one by one using a scan conversion algorithm
5) Count pixels calculating the sunlit and shade fractions

For more detailed information, see Yongtao Guan's Thesis