Location: Horticultural Crops ResearchTitle: A scalable plant-resolving radiative transfer model based on optimized GPU ray tracing
|BAILEY, BRIAN - University Of Utah|
|OVERBY, MATT - University Of Utah|
|WILLEMSEN, PETE - University Of Utah|
|PARDYJAK, ERIC - University Of Utah|
|Mahaffee, Walter - Walt|
|STOLL, ROB - University Of Utah|
Submitted to: Agriculture and Forest Meterology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2014
Publication Date: 11/1/2014
Citation: Bailey, B., Overby, M., Willemsen, P., Pardyjak, E.R., Mahaffee, W.F., Stoll, R. 2014. A scalable plant-resolving radiative transfer model based on optimized GPU ray tracing. Agriculture and Forest Meterology. 198-199:192-208. doi.org/10.1016/j.agrformet.2014.08.012.
Interpretive Summary: Graphics processing capabilities of computer video cards were used to develop faster and improved methods for estimating sun exposure of individual leaves in computer simulation models using 3d models of grape vines. These methods will further development of a vineyard simulation software package that can be used to examine how management decisions impact disease development. The simulation software can then be used, similar to how they are used in engineering, to inexpensively test and refine approaches before conducting expensive field trials. The models will also be useful in estimating how climate change will impact vineyard production and how to mitigate those effects.
Technical Abstract: A new model for radiative transfer in participating media and its application to complex plant canopies is presented. The goal was to be able to efficiently solve complex canopy-scale radiative transfer problems while also representing sub-plant heterogeneity. In the model, individual leaf surfaces are not resolved, but rather vegetation is aggregated into isothermal volumes. Using the leaf angle distribution and leaf area density functions, the volumes realistically augment the radiation field through absorption and anisotropic scattering and re-emission. The volumes are grouped to form individual plants, and individual plants are grouped to form entire canopies. The model increases efficiency by performing ray tracing calculations on graphics processing units (GPUs) using the NVIDIAR OptiXTM and CUDATM frameworks, and through efficient algorithms for radiation reflection, scattering, and emission. This efficiency allows for realistic representation of heterogeneity, while also allowing for the solution of problems with very large domains (' 105 trees) quickly on an inexpensive desktop workstation. Problem execution time scaled nearly linearly with the number of discrete elements in the domain. Model results are compared with experimental data collected from an array of radiation sensors within and above a grapevine canopy and an isolated tree. Agreement between simulated and measured values of shortwave and longwave radiation were very good, with model predictions generally within the expected measurement accuracy.