Renderings of diffraction effects observed in surface reflectance of a few common materials. (a) – (c) Proposed data-driven rendering results. (a) Diffraction patterns produced by an HTC 8X phone screen due to complex environmental illumination. (b, c) Diffraction patterns due to a point light source: (b) Bragg diffraction produced by a laptop (Lenovo Yoga) LCD screen, and (c) diffraction on a holographic paper. (d) Diffraction grating of an LG G3 phone screen measured using proposed “bokeh” photography and the resulting diffraction pattern rendered using a first order approximation (bottom right).
Figure : Renderings of diffraction effects observed in surface reflectance of a few common materials. (a) – (c) Proposed data-driven rendering results. (a) Diffraction patterns produced by an HTC 8X phone screen due to complex environmental illumination. (b, c) Diffraction patterns due to a point light source: (b) Bragg diffraction produced by a laptop (Lenovo Yoga) LCD screen, and (c) diffraction on a holographic paper. (d) Diffraction grating of an LG G3 phone screen measured using proposed “bokeh” photography and the resulting diffraction pattern rendered using a first order approximation (bottom right).


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. Secondly, 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.

The code to generate the lookup tables from measurements of a diffraction pattern at a single wavelength is available on my github.


References

[1] Practical Acquisition and Rendering of Diffraction Effects in Surface Reflectance. Antoine Toisoul and Abhijeet Ghosh. ACM Transactions on Graphics, 36(5), 2017.