Browsing by Author "Zhu, Junqiu"

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    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.
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    Real‐Time Microstructure Rendering with MIP‐Mapped Normal Map Samples
    (© 2022 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2022) Tan, Haowen; Zhu, Junqiu; Xu, Yanning; Meng, Xiangxu; Wang, Lu; Yan, Ling‐Qi; Hauser, Helwig and Alliez, Pierre
    Normal map‐based microstructure rendering can generate both glint and scratch appearance accurately. However, the extra high‐resolution normal map that defines every microfacet normal may incur high storage and computation costs. We present an example‐based real‐time rendering method for arbitrary microstructure materials, which significantly reduces the required storage space. Our method takes a small‐size normal map sample as input. We implicitly synthesize a high‐resolution normal map from the normal map sample and construct MIP‐mapped 4D position‐normal Gaussian lobes. Based on the above MIP‐mapped 4D lobes and a LUT (lookup table) data structure for the synthesized high‐resolution normal map, an efficient Gaussian query method is presented to evaluate ‐NDFs (position‐normal distribution functions) for shading. We can render complex scenes with glint and scratch surfaces in real time (30 fps) with a full high‐definition resolution, and the space required for each microstructure material is decreased to 30 MB.