BTF-based Material Representations: Current Challenges

The development of Bidirectional Texture Functions (BTFs) has made it possible for a wide range of different materials to acquire their characteristic appearance from a real-world counterpart and reproduce it faithfully in a high-quality rendering, that is hard to distinguish from an actual photograph. However, they have not yet found wide-spread use in practical applications. In this paper, we discuss, from our point of view, the main reasons for this and which unanswered questions and challenges for future research in this area remain. We focus on three different aspects: How can BTFs be measured and represented more efficiently? How can they be edited intuitively? And finally, can we find a perceptual difference metric between materials?