Light scattering from human hair fibers

Abstract

Light scattering from hair is normally simulated in computer graphics using Kajiya and Kay's classic phenomenological model. We have made new measurements of scattering from individual hair fibers that exhibit visually significant effects not predicted by Kajiya and Kay's model. Our measurements go beyond previous hair measurements by examining out-of-plane scattering, and together with this previous work they show a multiple specular highlight and variation in scattering with rotation about the fiber axis. We explain the sources of these effects using a model of a hair fiber as a transparent elliptical cylinder with an absorbing interior and a surface covered with tilted scales. Based on an analytical scattering function for a circular cylinder, we propose a practical shading model for hair that qualitatively matches the scattering behavior shown in the measurements. In a comparison between a photograph and rendered images, we demonstrate the new model's ability to match the appearance of real hair.

Wide-Baseline Hair Capture Using Strand-Based Refinement

“…1) due to the challenging wide-baseline setup. Quantitative evaluation To quantitatively evaluate our method, we use the hair models by [28] and render them using the hair appearance model in [17], as shown in Fig. 9.…”

“…For instance, omni-present occlusions and complex strand geometry preclude general surface-based smoothness priors [26] for hair reconstruction. The highly specular nature of hair [17] also violates the Lambertian surface assumption employed in most multi-view stereo methods. Consequently, many practical systems have either completely avoided hair reconstruction during facial capture (e.g.…”

Techniques of Facial Synthesis: A Comprehensive Literature Review

“…In 2001,Yu [71] used a 3D vector field for hairstyle modeling.They introduced a set of vector field primitives for both global and local control of hairstyles.In 2002,Chang et al [72] developed a system to model the interactions of the hair strands by applying dynamics simulation on a sparse set of guide strands.In 2003,Marschner et al [73] measured lights scattering from hair fibers and proposed a hair shading model that is more accurate than the model proposed by Kay [74].…”

Practical Global Illumination for Hair Rendering

“…Considering highly realistic hair rendering, Marschner et al have studied the scattering properties for human hair [5]. Zinke et al have introduced a model for the local scattering effects evident in some hair types [11].…”

“…A Type3 path may include many instances of forward scattering both before and after the non-forward scattering. This non-forward scattering drops the intensity of the light along the path at least an order of magnitude [5]. Therefore, even if the path does not include any forward scattering, the final intensity of a Type3 path can only be as high as 10% of the direct illumination.…”