42-Issue 4

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/2633354

Browse

Browsing 42-Issue 4 by Subject "CCS Concepts: Computing methodologies -> Reflectance modeling"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Neural Free-Viewpoint Relighting for Glossy Indirect Illumination
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Raghavan, Nithin; Xiao, Yan; Lin, Kai-En; Sun, Tiancheng; Bi, Sai; Xu, Zexiang; Li, Tzu-Mao; Ramamoorthi, Ravi; Ritschel, Tobias; Weidlich, Andrea
    Precomputed Radiance Transfer (PRT) remains an attractive solution for real-time rendering of complex light transport effects such as glossy global illumination. After precomputation, we can relight the scene with new environment maps while changing viewpoint in real-time. However, practical PRT methods are usually limited to low-frequency spherical harmonic lighting. Allfrequency techniques using wavelets are promising but have so far had little practical impact. The curse of dimensionality and much higher data requirements have typically limited them to relighting with fixed view or only direct lighting with triple product integrals. In this paper, we demonstrate a hybrid neural-wavelet PRT solution to high-frequency indirect illumination, including glossy reflection, for relighting with changing view. Specifically, we seek to represent the light transport function in the Haar wavelet basis. For global illumination, we learn the wavelet transport using a small multi-layer perceptron (MLP) applied to a feature field as a function of spatial location and wavelet index, with reflected direction and material parameters being other MLP inputs. We optimize/learn the feature field (compactly represented by a tensor decomposition) and MLP parameters from multiple images of the scene under different lighting and viewing conditions. We demonstrate real-time (512 x 512 at 24 FPS, 800 x 600 at 13 FPS) precomputed rendering of challenging scenes involving view-dependent reflections and even caustics.
  • Thumbnail Image
    Item
    A Practical and Hierarchical Yarn-based Shading Model for Cloth
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Zhu, Junqiu; Montazeri, Zahra; Aubry, Jean-Marie; Yan, Ling-Qi; Weidlich, Andrea; Ritschel, Tobias; Weidlich, Andrea
    Realistic cloth rendering is a longstanding challenge in computer graphics due to the intricate geometry and hierarchical structure of cloth: Fibers form plies which in turn are combined into yarns which then are woven or knitted into fabrics. Previous fiber-based models have achieved high-quality close-up rendering, but they suffer from high computational cost, which limits their practicality. In this paper, we propose a novel hierarchical model that analytically aggregates light simulation on the fiber level by building on dual-scattering theory. Based on this, we can perform an efficient simulation of ply and yarn shading. Compared to previous methods, our approach is faster and uses less memory while preserving a similar accuracy. We demonstrate both through comparison with existing fiber-based shading models. Our yarn shading model can be applied to curves or surfaces, making it highly versatile for cloth shading. This duality paired with its simplicity and flexibility makes the model particularly useful for film and games production.