A Composite BRDF Model for Hazy Gloss

Abstract

We introduce a bidirectional reflectance distribution function (BRDF) model for the rendering of materials that exhibit hazy reflections, whereby the specular reflections appear to be flanked by a surrounding halo. The focus of this work is on artistic control and ease of implementation for real-time and off-line rendering. We propose relying on a composite material based on a pair of arbitrary BRDF models; however, instead of controlling their physical parameters, we expose perceptual parameters inspired by visual experiments [VBF17]. Our main contribution then consists in a mapping from perceptual to physical parameters that ensures the resulting composite BRDF is valid in terms of reciprocity, positivity and energy conservation. The immediate benefit of our approach is to provide direct artistic control over both the intensity and extent of the haze effect, which is not only necessary for editing purposes, but also essential to vary haziness spatially over an object surface. Our solution is also simple to implement as it requires no new importance sampling strategy and relies on existing BRDF models. Such a simplicity is key to approximating the method for the editing of hazy gloss in real-time and for compositing.

An inverse method for the exploration of layered material appearance

“…The control of several rough lobes has been studied in the context of BRDF shop [Colbert et al 2006], making use of a painting interface. The particular relationship between a pair of BRDF lobes leading to hazy gloss effects has been studied by Barla et al [2018], along with a visual-to-physical parameter mapping. All these methods have in common that they only deal with a single more complex interface.…”

“…Compared to a single interface with a mix of microfacet distributions [Barla et al 2018], a layered material offers the opportunity to choose the base lobe (and hence the haze) color independently. Figure 20 demonstrates this with a pair of materials, each made of two dielectric lobes: a smooth 2-layer coat over a rough 1-layer base.…”

An inverse method for the exploration of layered material appearance

“…Publication date: August 2021. control of several rough lobes has been studied in the context of BRDF shop [Colbert et al 2006], making use of a painting interface. The particular relationship between a pair of BRDF lobes leading to hazy gloss effects has been studied by Barla et al [2018], along with a visual-to-physical parameter mapping. All these methods have in common that they only deal with a single more complex interface.…”

“…In this specific case, once an initial hazy conductor has been obtained through our method, varying the haze only affects the roughness of the bottom interface (this is not the case with a 2-layer base lobe, as explained in supplemental material). Compared to a single interface with a mix of microfacet distributions [Barla et al 2018], a layered material offers the opportunity to choose the base lobe (and hence the haze) color independently. Figure 20 demonstrates this with a pair of materials, each made of two dielectric lobes: a smooth 2-layer coat over a rough 1-layer base.…”

Microsurface Transformations

“…Notably, the GTR distribution is not part of this classification. Recently, Barla et al [BPV18] presented a technique that combines two BRDFs to provide more control on the tails of the distribution. Similarly, our technique modifies existing BRDFs and can be employed on top of their technique when their input BRDFs are microfacet‐based.…”