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# Développement d'un modèle de radiosité mixte pour simuler la distribution du rayonnement dans les couverts végétaux

Abstract : Light regulates many facets of plant growth and development through both quantitative effects of total energy (photosynthesis) and spectral quality (photomorphogenesis). Light also contributes to the global energy budget and thus to temperature. Several crop models treat the plant canopy as a single plant that takes the mean features of the plant population. A more realistic approach considers the canopy as a population of individual, interacting plants. This approach enables the study of plant competitions like competition for light. The new crop models need a more spatially accurate radiative budget than the mean plant models. The existing radiative models were developed for the homogeneous, non-interacting plant models. The old radiative models consider the canopy as a turbid medium and compute a radiative budget with the linear Bolzmann transport equation that is spatially integrated and not distributed by plant organs. The advantage of these models are speed and the ability to deal with big canopies. Frequently used computer graphics models, such as radiosity'', compute implicitly the spatial distribution of light intensity within the canopies. Their drawbacks are their inability to deal with big canopies and their requirement in computer memory and time. Here we investigate a new approach that we called nested radiosity. It mixes SAIL, a turbid medium model (TMM) and a radiosity model. We distinguish distant and nearby illumination. Light reflected from distant organs is computed with a quick TMM, and light regime provided by nearby surfaces is computed with an accurate radiosity model. Our model enables the computation of a canopy distributed radiative budget with a moderate computer time. Furthermore for a given canopy geometry we can compute without additional computer time several radiative conditions (wavelength, sun position,...), because form factors need not to be recalculated to be used with many different radiative parameters. For the validation of our model, we have developed a Monte Carlo ray tracing. We show good validation between our model and Monte Carlo simulations of typical cases.
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https://hal.inrae.fr/tel-02841953
Contributor : Michaël CHELLE Connect in order to contact the contributor
Submitted on : Tuesday, June 21, 2022 - 1:55:24 PM
Last modification on : Wednesday, June 22, 2022 - 3:23:49 AM

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chelle1997-these.pdf
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### Identifiers

• HAL Id : tel-02841953, version 2

### Citation

Michaël Chelle. Développement d'un modèle de radiosité mixte pour simuler la distribution du rayonnement dans les couverts végétaux. Informatique [cs]. Université de Rennes 1, 1997. Français. ⟨NNT : ⟩. ⟨tel-02841953v2⟩

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