Quasi-Monte Carlo simulation of the light environment of plants

The distribution of light in the canopy is a major factor regulating the growth and development of a plant. The main variables of interest are the amount of photosynthetically active radiation (PAR) reachingdifferent elements of the plant canopy, and the quality (spectral composition) of light reaching these elements. A light environment model based onMonte Carlo (MC) path tracing of photons, capable of computing both PARand the spectral composition of light, was developed by M ech (1997), and can be conveniently interfaced with virtual plants expressed using the open L-system formalism. To improve the efficiency of the light distribution calculations provided byM ech’sMonteCarlo program,we have implemented a similar programQuasiMC, which supports amore efficient randomised quasi-MonteCarlo samplingmethod (RQMC).We have validated QuasiMC by comparing it with MonteCarlo and with the radiosity-based CARIBU software (Chelle et al. 2004), andwe show that these two programs produce consistent results.We also assessed the performance of theRQMCpath tracing algorithm by comparing it with Monte Carlo path tracing and confirmed that RQMC offers a speed and/or accuracy improvement over MC. Additional keywords: light simulation, open L-system, PAR, path tracing, red/far red ratio, (randomised) quasi-Monte Carlo sampling, variance reduction, virtual plant modelling.