混合神经与微表面模型,实现高效高保真实时渲染。
A Hybrid Neural-Microfacet BRDF Model for Real-Time Rendering

- 用神经网络修正微表面模型的外观误差,降低网络规模。
- 相同内存下,对实测数据的逼近优于现有神经模型。
- 兼顾艺术家可编辑性与高效采样,适合实时与离线渲染。
过去十年,基于微表面的BRDF模型构成了实时渲染管线的基础。尽管应用广泛,它们常无法再现复杂光-表面相互作用带来的细微视觉效果,从而催生了针对特定光学现象(如衍射、虹彩、多层结构)的专用物理模型。尽管更精确,这些模型牺牲了通用性且难以满足实时渲染性能要求。近期出现的神经模型已证明能有效拟合来自测量、仿真或复杂着色网络的BRDF数据。然而,大多数现有神经模型需要较大网络,成本高昂。本文提出一种混合模型,结合GGX型微表面模型与神经模型,融合二者优势。神经组件用于修正微表面组件的外观表现,使网络规模显著减小。实验表明,在相同内存开销下,本模型对实测数据的逼近效果优于当前最优神经模型,同时评估开销远低于纯微表面模型。此外,该混合模型仍易于艺术家编辑,并支持高效的采样策略,适用于离线与实时渲染。
原文摘要 · Abstract (English)
Over the past decade, microfacet-based BRDF models have formed the foundation of real-time rendering pipelines. Despite their widespread use, they often fail to reproduce subtle appearance effects arising from complex light-surface interactions, which have led to the emergence of specialized physics-based models for specific optical phenomena (e.g., diffraction, iridescence, multilayers). Although more accurate, these models lose versatility and lack performance for real-time rendering. Recently introduced, neural models have demonstrated their ability to approximate BRDF reference data coming from measurements, simulations, or even complex shading networks. However, most current neural models require relatively large networks, making them costly for real-time rendering. In this paper, we introduce a hybrid model that combines a GGX-type microfacet model and a neural model to leverage the best features of both representations. The neural component corrects the appearance approximated by the microfacet component, allowing much smaller network than in existing neural models. We show that, at identical memory cost, our model approximates measurements better than state-of-the-art neural models for a low evaluation overhead compared to a microfacet-based model. Furthermore, our hybrid model remains easily editable by artists and benefits from an important sampling scheme, making it attractive for both offline and real-time rendering.
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