Article Preview
TopOur work is most related to techniques for accelerating the rendering process through the use of acceleration structures, techniques for handling hair transparency and simulating the hair's properties and ray bundle techniques.
Studies for accelerating the rendering process have focused on structures such as grids (Amanatides & Woo, 1987; Cleary & Wyvill, 1988; Wald et al., 2006), kd-trees (Shevtsov et al., 2007) and bounding volume hierarchies (Kay & Kajiya, 1986). More recently, we have seen an increase in techniques for fast GPU construction of BVHs (Karras, 2012; Karras & Aila, 2013) as well as techniques for reducing the number of intersection tests through the use of a hybrid BVH of AABBs and OBBs (Woop et al., 2014).
Techniques for handling hair transparency and simulating the hair's properties have also been developed, falling in one of two categories: on the one hand, we have pure physical models, such as path tracing (Kajiya, 1986) and bi-directional path tracing (Lafortune, 1993) and photon mapping (Jensen, 1996a; Jensen, 1996b; Jensen & Christensen, 1998; Moon & Marschner, 2006). Several techniques have also been proposed to simulate the hair's properties, with scattering models for single hair fibers (Marschner et al., 2003; d'Eon et al., 2013; Pekelis et al., 2015), multiple scattering (Zinke et al., 2008) and natural illumination (Ren et al., 2010). Recently, we have also witnessed an increase in the studies focusing on the animation of hair scenes in real time, with the AMD TressFx technique (Lacroix, 2013; Martin et al., 2014) and techniques for the animation of hair scenes with data-driven interpolation of guide strands (Chai et al., 2014) and by bundling hair fibers into hair meshes (Wu et al., 2016).