A generic framework for physical light transport

Steinberg, Shlomi; Yan, Ling‐Qi

doi:10.1145/3450626.3459791

Cited by 21 publications

(6 citation statements)

References 43 publications

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“…The speckle effect results from the interference of many waves with varying phases and amplitudes but with the same frequency. A similar effect can also be observed when illuminating with partially coherent light [YHW*18, SY21], e.g. natural light.…”

Section: Observationsmentioning

confidence: 56%

Investigation and Simulation of Diffraction on Rough Surfaces

Clausen

Chen

Fuhrmann

et al. 2022

Computer Graphics Forum

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Simulating light-matter interaction is a fundamental problem in computer graphics. A particular challenge is the simulation of light interaction with rough surfaces due to diffraction and multiple scattering phenomena. To properly model these phenomena, wave-optics have to be considered. Nevertheless, the most accurate BRDF models, including wave-optics, are computationally expensive, and the resulting renderings have not been systematically compared to real-world measurements. This work sheds more light on reflectance variations due to surface roughness. More specifically, we look at wavelength shifts that lead to reddish and blueish appearances. These wavelength shifts have been scarcely reported in the literature, and, in this paper, we provide the first thorough analysis from precise measured data. We measured the spectral in-plane BRDF of aluminium samples with varying roughness and further acquired the surface topography with a confocal microscope. The measurements show that the rough samples have, on average, a reddish and blueish appearance in the forward and back-scattering, respectively. Our investigations conclude that this is a diffraction-based effect that dominates the overall appearance of the samples. Simulations using a virtual gonioreflectometer further confirm our claims. We propose a linear model that can closely fit such phenomena, where the slope of the wavelength shifts depends on the incident and reflection direction. Based on these insights, we developed a simple BRDF model based on the Cook-Torrance model that considers such wavelength shifts.

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Section: Observationsmentioning

confidence: 56%

Investigation and Simulation of Diffraction on Rough Surfaces

Clausen

Chen

Fuhrmann

et al. 2022

Computer Graphics Forum

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“…Partially-coherent light transport. Physical light transport (PLT) was introduced over the recent years by ; Steinberg and Yan [2021a]. In contrast to work that aims to reproduce the appearance of a particular wave-interference effect by simulating the wave-optical interaction locally, at the BSDF level, PLT takes a global approach: it propagates the optical coherence of light throughout the scene.…”

Section: Related Workmentioning

confidence: 99%

“…Recognizing that the partial coherence of light plays a crucial role in the observable appearance of materials, physical light transport (PLT) was introduced Steinberg and Yan 2021a] as a framework that enables practical wave-optical light transport. PLT understands light as a collection of partially coherent, but mutually-incoherent, beams of light (Fig.…”

Section: Introductionmentioning

confidence: 99%

A Generalized Ray Formulation For Wave-Optics Rendering

Steinberg¹,

Ramamoorthi²,

Bitterli³

et al. 2023

Preprint

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Fig. 1. From ray optics to wave optics. In this paper we present the generalized ray: an extension of the classical ray to wave optics. The generalized ray retains the defining characteristics of the ray-optical ray: locality and linearity. These properties allow the generalized ray to serve as a "point query" of light's behaviour-the same purpose that the classical ray fulfils in rendering. By using such generalized rays, we enable the rendering of complex scenes, like the one shown, under rigorous wave-optical light transport. Materials admitting diffractive optical phenomena are visible: (a) a Bornite ore with a layer of copper oxide causing interference; (b) a Brazilian Rainbow Boa, whose scales are biological diffraction grated surfaces; and (c) a Chrysomelidae beetle, whose colour arises due to naturally-occurring multilayered interference reflectors in its elytron. Our formalism serves as a link between path tracing techniques and wave optics, and admits a highly general validity domain. Therefore, we are able to apply sophisticated sampling techniques, and achieve performance that surpasses the state-of-the-art by orders-of-magnitude. We indicate resolution and samples-per-pixel (spp) count in all figures rendered using our method. While these figures showcase converged (high spp) results, our implementation also allows interactive rendering of all these scenes at 1 spp. Frame times (at 1 spp) for interactive rendering are indicated. Implementation, as well as additional renderings and videos are available in our supplemental material. Under ray-optical light transport, the classical ray serves as a local and linear "point query" of light's behaviour. Such point queries are useful, and sophisticated path tracing and sampling techniques enable efficiently computing solutions to light transport problems in complex, real-world settings and environments. However, such formulations are firmly confined to the realm of ray optics, while many applications of interest, in computer graphics and computational optics, demand a more precise understanding of light. We rigorously formulate the generalized ray, which enables local and linear point queries of the wave-optical phase space. Furthermore, we present sample-solve: a simple method that serves as a novel link between path tracing and computational optics. We will show that this link enables the

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“…Guillén et al [GMG*20] developed a material model for pearlescent materials. Beyond wave‐based scattering models, researchers have also applied wave optics to the light transport problem [SSY22; SY21]. In our work, we focus on the material level, specifically the wave optics effects produced by spherical particles and specular surfaces.…”

Section: Related Workmentioning

confidence: 99%

Iridescent Water Droplets Beyond Mie Scattering

Xia

Walter

Marschner

2023

Computer Graphics Forum

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Looking at a cup of hot tea, an observer can see color patterns and granular textures both on the water surface and in the steam. Motivated by this example, we model the appearance of iridescent water droplets. Mie scattering describes the scattering of light waves by individual spherical particles and is the building block for both effects, but we show that other mechanisms must also be considered in order to faithfully reproduce the appearance. Iridescence on the water surface is caused by droplets levitating above the surface, and interference between light scattered by drops and reflected by the water surface, known as Quetelet scattering, is essential to producing the color. We propose a model, new to computer graphics, for rendering this phenomenon, which we validate against photographs. For iridescent steam, we show that variation in droplet size is essential to the characteristic color patterns. We build a droplet growth model and apply it as a post‐processing step to an existing computer graphics fluid simulation to compute collections of particles for rendering. We significantly accelerate the rendering of sparse particles with motion blur by intersecting rays with particle trajectories, blending contributions along viewing rays. Our model reproduces the distinctive color patterns correlated with the steam flow. For both effects, we instantiate individual droplets and render them explicitly, since the granularity of droplets is readily observed in reality, and demonstrate that Mie scattering alone cannot reproduce the visual appearance.

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A generic framework for physical light transport

Cited by 21 publications

References 43 publications

Investigation and Simulation of Diffraction on Rough Surfaces

Investigation and Simulation of Diffraction on Rough Surfaces

A Generalized Ray Formulation For Wave-Optics Rendering

Iridescent Water Droplets Beyond Mie Scattering

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