Practical Measurement-based Modeling and Rendering of Surface Diffraction
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2019
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Abstract
Computer graphics have evolved at a very fast pace over the last forty years. Most of the research in rendering has been focused on recreating visual effects that can be explained with geometric optics, such as reflections from diffuse and specular surfaces, refraction and volumetric scattering. Although geometric optics cover a wide range of effects related to light transport, some very impressive and colourful effects can only be explained and rendered with wave optics. This is the case of diffraction of light. Diffraction is a very common effect that causes dispersion of light i.e., the decomposition of white light into colourful patterns on a surface. It is caused by interferences between light waves when the geometry of a surface reaches a size below the coherence length of white light (around 65 micrometers). The most famous example of a diffractive surface is probably a Compact Disc on which the bits of information are stored along tracks that are small enough to diffract light. In this thesis, we present novel approaches to generate photorealistic computer renderings of diffraction of light from measurements of real-world surfaces. We present four practical measurement setups that employ commonly found hardware to acquire reflectance properties of both spatially-homogeneous diffractive surfaces and spatially-varying printed holographic surfaces. We also describe how such measurements can be employed in conjunction with a physically-based rendering model of diffraction to avoid Fourier optics simulations and therefore reduce the computational expense of diffraction rendering. Finally, we present techniques to render diffraction effects under arbitrary illumination at real-time framerates which is computationally very expensive with conventional techniques. These contributions constitute the first demonstration of realistic renderings of complex diffraction patterns observed in manufactured materials using practical measurement techniques at the interface of photography and optics. The algorithms presented in this thesis can be implemented in real-time applications such as video games and virtual reality experiences.
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