Rendering 2024 - Symposium Track

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https://diglib.eg.org/handle/10.2312/3607012

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Browsing Rendering 2024 - Symposium Track by Subject "> Rendering"

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    Constrained Spectral Uplifting for HDR Environment Maps
    (The Eurographics Association, 2024) Tódová, Lucia; Wilkie, Alexander; Haines, Eric; Garces, Elena
    Spectral representation of assets is an important precondition for achieving physical realism in rendering. However, defining assets by their spectral distribution is complicated and tedious. Therefore, it has become general practice to create RGB assets and convert them into their spectral counterparts prior to rendering. This process is called spectral uplifting. While a multitude of techniques focusing on reflectance uplifting exist, the current state of the art of uplifting emission for image-based lighting consists of simply scaling reflectance uplifts. Although this is usable insofar as the obtained overall scene appearance is not unrealistic, the generated emission spectra are only metamers of the original illumination. This, in turn, can cause deviations from the expected appearance even if the rest of the scene corresponds to real world data. We propose a method capable of uplifting HDR environment maps based on spectral measurements of light sources similar to those present in the maps. To identify the illuminants, we employ an extensive set of emission measurements, and we combine the results with an existing reflectance uplifting method. In addition, we address the problem of environment map capture for the purposes of a spectral rendering pipeline, for which we propose a novel solution.
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    Precomputed Dynamic Appearance Synthesis and Rendering
    (The Eurographics Association, 2024) Bai, Yaoyi; Hasan, Miloš; Yan, Ling-Qi; Haines, Eric; Garces, Elena
    Interpolation between objects of varying dimensionality is a common task in computer graphics; however, high-quality dynamic natural interpolation for appearance remains scarce. In this paper, we propose a blending framework for general appearances that can be integrated into renderers without modifying the rendering pipeline. For natural interpolation calculations, we use the mathematical tool optimal transport (OT), known for its promising blending quality. Although recent advancements in OT theory have improved computational performance, integrating runtime OT calculations into the path tracing rendering pipeline compromises algorithm efficiency and increases storage requirements. To address this, we propose a novel solution that precomputes appearances into a proxy distribution and introduces a hierarchical query structure. This enables efficient online point or range data querying, allowing for the generation or retrieval of large data sets as needed. Additionally, the proxy and hierarchical query structure facilitate multi-way barycenter computation. With this efficient query structure and barycentric calculation, we demonstrate several applications of our method, including 2D and 3D interpolation, as well as isotropic BRDF interpolation.
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    ReSTIR FG: Real-Time Reservoir Resampled Photon Final Gathering
    (The Eurographics Association, 2024) Kern, René; Brüll, Felix; Grosch, Thorsten; Haines, Eric; Garces, Elena
    Achieving real-time global illumination for a given scene remains challenging, even with the advent of hardware ray tracing, due to the substantial quantity of rays required. To enhance the quality of the limited number of samples, spatial and temporal resampling can be used. The concept of resampling gained popularity with ReSTIR DI [BWP*20], enabling real-time direct illumination for scenes with millions of lights. This concept was further extended by combining it with path tracing to quickly approximate the indirect illumination (ReSTIR GI [OLK*21]) or correctly approximate global illumination (ReSTIR PT [LKB*22] and Suffix ReSTIR [KLR*23]). However, these algorithms fall short in effectively rendering caustic effects -bundles of reflected or refracted light- often associated with photon mapping. We introduce ReSTIR FG, an efficient real time indirect illumination algorithm that combines photon final gathering with the principles of ReSTIR. First, we introduce an efficient photon final gathering scheme, enabling quick consistent offline rendering. Then we combine our photon final gathering with spatiotemporal resampling to allow for real time global illumination. Our algorithm is capable of displaying multi bounce indirect illumination, as well as caustic effects, while remaining competitive in both runtime and quality when compared to the aforementioned state-of-the-art global illumination resampling techniques.