A wave optics based fiber scattering model

Realistic hair rendering relies on fiber scattering models. These models are based on either ray tracing or on full wave‐propagation through the hair fiber. Ray tracing can model most of the scattering phenomenon observed but misses the important effect of diffraction. Indeed human natural hair specific dimensions and geometry demands for the wave nature of light to be taken into consideration for accurate rendering. However, current full‐wave model requires nonpratical, several days precomputation, that needs to be repeated for every change in the hair geometry or color, for appropriate results. We present in this paper a dual hair scattering model which considers the dual aspect of light: as a wave and as a ray. Our model accurately simulates both diffraction and scattering phenomena without requiring any precomputation. Furthermore, it can simulate light transport in hairs of arbitrary elliptical cross‐sections. This new dual approach enables our model to significantly improve the appearance of rendered hair and qualitatively match scattering and diffraction effects seen in photos of real hair while adding little computation overhead.

Section: Resultssupporting

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

See 3 more Smart Citations

A combined scattering and diffraction model for elliptical hair rendering

Benamira

Pattanaik

2021

A Microfacet‐based Hair Scattering Model

Huang

Hullin

Hanika

2022

Figure 1: Detail of a backlit studio scene rendered using a state-of-the-art separable hair scattering model (A) and the proposed model (C), both compared with a photograph under similar lighting conditions (B) (© Martyn Thompson https://photographymk.co.uk), with visualization of the BCSDF (a,c) as plotted against θo/ϕo, illumination angle θ i = 0. The strongly focused reflection in the forward scattering direction seen in (C,c) gives rise to a glint-like appearance that the previous separable hair scattering models have been unable to capture. (Exposure of (a,c) is scaled up by 2.5 stops to improve feature visibility. (A,C) are close-up images of Fig. 13.

Iridescent Water Droplets Beyond Mie Scattering

Xia

Walter

Marschner

2023

Self Cite

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.