Acquisition, Synthesis, and Rendering of Bidirectional Texture Functions

Abstract

One of the main challenges in computer graphics is still the realistic rendering of complex materials such as fabric or skin. The difficulty arises from the complex meso structure and reflectance behavior defining the unique look-and-feel of a material. A wide class of such realistic materials can be described as 2D-texture under varying light-and view direction, namely, the Bidirectional Texture Function (BTF). Since an easy and general method for modeling BTFs is not available, current research concentrates on image-based methods, which rely on measured BTFs (acquired real-world data) in combination with appropriate synthesis methods. Recent results have shown that this approach greatly improves the visual quality of rendered surfaces and therefore the quality of applications such as virtual prototyping. This state-of-the-art report (STAR) will present the techniques for the main tasks involved in producing photo-realistic renderings using measured BTFs in details.

WebGL-based streaming and presentation of objects with bidirectional texture functions

“…Each of the columns of U can now be regarded as a tabulated representation of one of the functions u (c) (ω i , ω o ) and analogously the columns of V as representations of v (c) (x). Thus, in this approximation, C denotes the number of columns or components (SVD and PCA are closely related and the term component is in common use in the field of BTF compression [Müller et al 2004]). S is a diagonal matrix, which can be stored by multiplication either with U or V. Due to the diagonality property, this corresponds to a scaling of the respective components, e.g.…”

Real-Time Visualization of a Sparse Parametric Mixture Model for BTF Rendering

“…Most real world materials exhibit complex appearance that can be described at three levels [2,9]. The macroscale is the large scale geometry of the object, traditionally modeled with explicit representations, such as polygon meshes.…”

“…For that, BTFs, an image driven approach, are often used instead. A Bidirectional Subsurface Scattering Reflectance Distribution Function (BSSRDF) can model all these light phenomena, but is much too complex to be usable in interactive rendering pipelines, and current capturing systems only allow to measure subsets of this function [1,2].…”

“…Parametric Bidirectional Reflectance Distribution Functions (BRDF) are often used to model a material's appearance, but they cannot simulate many complex lighting phenomena such as self-shadowing, self-occlusion, sub-surface scattering and inter-reflections. Instead, image based approaches, such as the Bidirectional Texture Function (BTF), are becoming ever more popular due to the realism they can provide, the improvement in acquisition systems quality and the increasing computational power of GPUs [1][2][3].…”

“…A single BTF can take up several gigabytes of storage, too much to be of practical use in real-time rendering. To tackle this problem, the BTF data must be transformed into a compact and efficiently renderable representation, without compromising image fidelity [2,3,[5][6][7]. Wu et al [8] presented a novel general representation for BTFs, the Sparse Parametric Mixture Model (SPMM).…”