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Light interreflexions in ridged surfaces : influence of surface structure, material and lighting on color

Abstract : Light interreflections are an optical phenomenon that remains relatively Under-investigated, and happening on every non-planar surface, precisely in their big or small concavities, and that noticeably affects their color appearance : each illuminated point in a concavity is then illuminating the other points of the cavity. This process of mutual illumination can happen indefinitely on a scattering surface. It is crucial to acknowledge a high number of light successive reflections to correctly predict a structured material appearance, for example in the case of 3D printing. We propose models allowing the description of these interreflections with quasi-analytical solutions, Under the assumption that the surface is periodically ridged, made of infinitely long V-cavities, identical and parallel, made of opaque material. Three types of interreflection model were studied: Lambertian, mirror-like, and « interfaced » Lambertian materials. The results of the models allowed us to deeply investigate the influence of the shape, the lighting geometry and of the material on the perceived color and radiance. The Lambertian model put the emphasis on a gain in radiance and chroma in the case of highly reflective scattering materials, which can disappear with a change in lighting. The specular only model shows the saturation of the perceived color as a function of the number of specular reflections, and the influence of the polarization change on the color. The interfaced Lambertian model propose a more realistic approach for real life materials, with small differences with the predictions obtained with the Lambertian only model. These models are a useful toolbox to get an idea of the different parameters influencing the color, which evolution of the color to expect, and to what extent the influence is significant, and how to explain the physical reasons behind them. The described evolutions can be generalized to more complex surface structure than the one studied in this work.
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Submitted on : Monday, May 3, 2021 - 2:20:08 PM
Last modification on : Tuesday, May 4, 2021 - 3:24:01 AM

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  • HAL Id : tel-03215591, version 1

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Dorian Saint-Pierre. Light interreflexions in ridged surfaces : influence of surface structure, material and lighting on color. Optics [physics.optics]. Université de Lyon, 2020. English. ⟨NNT : 2020LYSES041⟩. ⟨tel-03215591⟩

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