When Does Directional Reflectance Matter? Evaluating BRDF Effects in Plant Canopy Light Simulations.

Area of Science:

• Plant science
• Optics
• Computer simulation

Background:

• Virtual plant models and ray-tracing are used for plant-light interaction studies.
• Current models often simplify leaf reflectance as diffuse, ignoring direction-dependent properties.

Purpose of the Study:

• To investigate the impact of incorporating measured, direction-dependent leaf reflectance (BRDF) into virtual plant models.
• To assess effects on light absorption and spectral composition under various lighting conditions.

Main Methods:

• Utilized 3D virtual cucumber plant models with PhongShader for optical leaf characteristics.
• Simulated light absorption and photon flux densities under diffuse and directed sunlight.
• Considered spectrally resolved and direction-dependent Bidirectional Reflectance Distribution Function (BRDF).

Main Results:

• Total leaf-level light absorption was marginally affected (MAPE < 2%).
• Spectral distortions in the canopy exceeded 8% in the blue wavelength range under direct light.
• Directional reflectance significantly impacts spectral composition within the plant canopy.

Conclusions:

• BRDF modeling is not critical for estimating photosynthetic rates in most scenarios.
• Accurate BRDF is essential for spectral analyses and optimizing artificial lighting in greenhouses.
• Simulating spectral composition is vital for optical sensor applications in controlled environments.