Practical acquisition and rendering of diffraction effects in surface reflectance

Abstract

We propose two novel contributions for measurement-based rendering of diffraction effects in surface reflectance of planar homogeneous diffractive materials. As a general solution for commonly manufactured materials, we propose a practical data-driven rendering technique and a measurement approach to efficiently render complex diffraction effects in real time. Our measurement step simply involves photographing a planar diffractive sample illuminated with an LED flash. Here, we directly record the resultant diffraction pattern on the sample surface due to a narrow-band point source illumination. Furthermore, we propose an efficient rendering method that exploits the measurement in conjunction with the Huygens-Fresnel principle to fit relevant diffraction parameters based on a first-order approximation. Our proposed data-driven rendering method requires the precomputation of a single diffraction look-up table for accurate spectral rendering of complex diffraction effects. Second, for sharp specular samples, we propose a novel method for practical measurement of the underlying diffraction grating using out-of-focus “bokeh” photography of the specular highlight. We demonstrate how the measured bokeh can be employed as a height field to drive a diffraction shader based on a first-order approximation for efficient real-time rendering. Finally, we also drive analytic solutions for a few special cases of diffraction from our measurements and demonstrate realistic rendering results under complex light sources and environments.