An unstructured lumigraph based approach to the SVBRDF estimation problem

• Published in: Computers & graphics 2020-12, Vol.93, p.95-107
• Main Authors: Andrade, Beatriz Trinchão, Resch, Benjamin, Lensch, Hendrik P.A., Bellon, Olga Regina Pereira, Silva, Luciano
• Format: Article
• Language: English
• Subjects: Appearance preservation; Digital preservation; Image acquisition; Information retrieval; Motion perception; Realistic rendering; Reflectance functions; SVBRDFs; Unstructured data; Unstructured lumigraphs; Virtual reality
• ISSN: 0097-8493; 1873-7684
• DOI: 10.1016/j.cag.2020.09.013

•Spatially variant surfaces can be digitally preserved using image-based processes.•SVBRDF estimation method uses solely HDR images of a scene as input.•Unstructured lumigraphs sample scene’s plenoptic function during SVBRDF estimation.•Considering that incoming light can change at each surface point provides precision.•Considering the environment as source of light provides a flexible acquisition setup. [Display omitted] Appearance preservation aims to estimate reflectance functions to model the way real materials interact with light. These functions are especially useful in digital preservation of heritage and realistic rendering, as they reproduce the appearance of real materials in virtual scenes. This work proposes an image-based process that aims to preserve the appearance of surfaces whose reflectance properties are spatially variant. During image acquisition, this process considers the whole environment as a source of light over the area to be preserved and, assuming the environment is static, it does not require controlled environments. To achieve this goal, the scene geometry and relative camera positions are approximated from a set of HDR images taken inside the real scene, using a combination of structure from motion and multi-view stereo methods. Based on this data, a set of unstructured lumigraphs is traced, on-demand, inside the reconstructed scene. The color information retrieved from these lumigraphs is then used to estimate a linear combination of basis BRDFs for a grid of points in the surface area, defining thus its SVBRDF. This paper details the proposed method and presents the results obtained using real and synthetic settings. It shows that considering the whole environment as a source of light is a viable approach to obtain reliable results and to enable more flexible acquisition setups.