Inverse shade trees for non-parametric material representation and editing

Abstract

Recent progress in the measurement of surface reflectance has created a demand for non-parametric appearance representations that are accurate, compact, and easy to use for rendering. Another crucial goal, which has so far received little attention, is editability: for practical use, we must be able to change both the directional and spatial behavior of surface reflectance (e.g., making one material shinier, another more anisotropic, and changing the spatial "texture maps" indicating where each material appears). We introduce an Inverse Shade Tree framework that provides a general approach to estimating the "leaves" of a user-specified shade tree from highdimensional measured datasets of appearance. These leaves are sampled 1-and 2-dimensional functions that capture both the directional behavior of individual materials and their spatial mixing patterns. In order to compute these shade trees automatically, we map the problem to matrix factorization and introduce a flexible new algorithm that allows for constraints such as non-negativity, sparsity, and energy conservation. Although we cannot infer every type of shade tree, we demonstrate the ability to reduce multigigabyte measured datasets of the Spatially-Varying Bidirectional Reflectance Distribution Function (SVBRDF) into a compact representation that may be edited in real time.

Analytic Double Product Integrals for All-Frequency Relighting

“…The spatial varying BRDF textures are obtained from the websites of the authors of [21], [22]. Based on our analytic double product integral, we achieve real-time frame rates while handling dynamic viewing, lighting, reflectance and high-frequency, per-pixel shading.…”

Efficient representation of bidirectional reflectance distribution functions for metallic paints considering manufacturing parameters

“…1,13 While using these representations, Lawrence et al 2 introduced a tree-based representation in which high dimensional BRDF data are approximated by several 1-D curves or 2-D terms. It makes the data compact and changes the reflectance behavior of a surface by allowing the user to edit the measured BRDF.…”

“…2 To increase the accuracy of decomposition, each measured BRDF is reparametrized to the half-angle (H) and the difference (D) coordinate [Rus98] where both the half-angle and the difference terms are the functions of two variables (θ ,φ) [see Fig. 10(b)].…”

“…Recent researchers [1][2][3][4] have introduced alternative methods in designing a new appearance material using the measured bidirectional reflectance distribution function (BRDF). Matusik et al 1 have shown the possibility of reconstructing a new material through linear combination of several materials having different reflectance properties.…”

“…On the other hand, material design methods by using one-dimensional (1-D) reflectance curves 2 and image-based material editing 3,4 have improved to handle a variety of materials. Lawrence et al 2 have introduced a material design method using 1-D and two-dimensional (2D) functions that describe the reflectance properties of individual materials. They decomposed high dimensional measured data by using a matrix factorization algorithm in order to obtain reflectance functions.…”