An overview of BRDF models (original) (raw)

A Survey of BRDF Models for Computer Graphics

To produce photo-realistic images in computer graphics, we must effectively describe the interactions between light and surfaces. In this paper, we focus on Bidirectional Reflectance Distribution Functions (BRDFs), which characterize these interactions. We survey on most BRDF representations introduced so far and we investigate their usage, importance and applications. We look at in detail their two important usages; in GPU-based real-time renderings and in renderings of metallic car paints.

An Anisotropic BRDF Model for Fitting and Monte Carlo Rendering

In this paper we propose a new physically plausible, anisotropic Bidirectional Reflectance Distribution Function (BRDF) for fitting and for importance sampling in global illumination rendering. We demonstrate that the new model is better in data fitting than existing BRDF models. We also describe efficient schemes for sampling the proposed anisotropic BRDF model. Furthermore, we test it on a GPU-based real-time rendering algorithm and show that material design can be done with this anisotropic BRDF model effectively. We also show that the new model has effective real-time rendering performance.

Efficient rendering of spatial bi-directional reflectance distribution functions

2002

Abstract We propose texture maps that contain at each texel all the parameters of a Lafortune representation BRDF as a compact, but quite general surface appearance representation. We describe a method for rendering such surfaces rapidly on current graphics hardware and demonstrate the method with real, measured surfaces and hand-painted surfaces. We also propose a method of rendering such spatial bi-directional reflectance distribution functions using prefiltered environment maps.

Monte Carlo Estimator for Image Creation with Symmetric Sampling of Phong BRDF Model

2010

The paper is directed to the advanced rendering techniques for realistic image creation. We construct and offer a new Monte Carlo estimator for numerical solution of the rendering equation based on Phong BRDF (Bidirectional Reflectance Distribution Function) model. We consider the kernel of Phong rendering equation and present the Monte Carlo solution by a sum of two independent integrals, one for diffuse and one for specular part respectively. The diffuse integral equation is solved by applying Combined Uniform Separation of integration domain to achieve variance reduction. The hemispherical integration domain is symmetrically separated into 8 sub-domains of equal orthogonal spherical triangles and 8 sub-domains of equal spherical quadrangles. All spherical triangles, spherical quadrangles respectively are symmetric each to other as well as have fixed vertices and computable parameters. The symmetric sampling scheme is applied to generate the sampling points and solve the diffuse integral equation. The integration domain of specular integral equation is approximated by conical solid angle of most important region of interest. The normal vector of the conical solid angle is the direction of ideally reflected by the surface viewing vector. We show that the conical solid angle can be successfully approximated with rotation of all orthogonal spherical triangles sub-domains, constructed at solving the diffuse integral equation, being easy to reuse the sampling points.

Generic brdf sampling: A sampling method for global illumination

2008

This paper introduces a new BRDF sampling method with reduced variance, which is based on a hierarchical adaptive parameterless PDF. This PDF is based also on rejection sampling with a bounded average number of trials, even in regions where the BRDF does exhibit high variations. Our algorithm works in an appropiate way with both physical and analytical reflectance models. Reflected directions are sampled by using importance sampling of the BRDF times the cosine term. This fact improves computation of reflected radiance when Monte-Carlo integration is used in Global Illumination. Test images have been obtained by using a Monte-Carlo rendering system, and they show reduced variance as compared with those obtained by other known techniques.

Efficient Modeling of Objects BRDF with Planned Sampling

IPSJ Transactions on Computer Vision and Applications, 2013

In this work we propose a novel method for modeling and synthesizing objects appearance based on planned sampling. The proposed method can efficiently model the BRDF of an object with uniform and isotropic reflectance using a small number of light source directions. This is achieved by utilizing together the knowledge of the object's shape along with the statistics of various BRDFs. The method considers the shape of the object, compact basis representing variations in a reflectance dataset, a fixed view direction and all possible light source directions around the object. Then using an iterative optimization process which simulates the contribution of each light source in modeling the object appearance, our method identifies the most suitable set of light source directions for efficiently modeling the BRDF of the object's material. The selected light sources are then used to acquire actual images of the object for recovering its reflectance properties. Experiments conducted using several objects with varying shapes and a small number of light sources optimally selected by the method validate the effectiveness of the proposed approach in modeling object appearance.

Compact and intuitive data-driven BRDF models

2020

Measured materials are rapidly becoming a core component in the photo-realistic image synthesis pipeline. The reason is that data-driven models can easily capture the underlying, fine details that represent the visual appearance of materials, which can be difficult or even impossible to model by hand. There are, however, a number of key challenges that need to be solved in order to enable efficient capture, representation and interaction with real materials. This paper presents two new data-driven BRDF models specifically designed for 1D separability. The proposed 3D and 2D BRDF representations can be factored into three or two 1D factors, respectively, while accurately representing the underlying BRDF data with only small approximation error. We evaluate the models using different parameterizations with different characteristics and show that both the BRDF data itself and the resulting renderings yield more accurate results in terms of both numerical errors and visual results compared to previous approaches. To demonstrate the benefit of the proposed factored models, we present a new Monte Carlo importance sampling scheme and give examples of how they can be used for efficient BRDF capture and intuitive editing of measured materials.

Efficient BRDF Sampling Using Projected Deviation Vector Parameterization

This paper presents a novel approach for efficient sampling of isotropic Bidirectional Reflectance Distribution Functions (BRDFs). Our approach builds upon a new pa-rameterization, the Projected Deviation Vector parameteri-zation, in which isotropic BRDFs can be described by two 1D functions. We show that BRDFs can be efficiently and accurately measured in this space using simple mechanical measurement setups. To demonstrate the utility of our approach, we perform a thorough numerical evaluation and show that the BRDFs reconstructed from measurements along the two 1D bases produce rendering results that are visually comparable to the reference BRDF measurements which are densely sampled over the 4D domain described by the standard hemispherical parameterization.

The halfway vector disk for BRDF modeling

ACM Transactions on Graphics, 2006

We present a mathematical framework for enforcing energy conservation in a BRDF by specifying halfway vector distributions in simple two-dimensional domains. Energy-conserving BRDFs can produce plausible rendered images with accurate reflectance behavior, especially near grazing angles. Using our framework, we create an empirical BRDF that allows easy specification of diffuse, specular, and retroreflective materials. We also present a second BRDF model that is useful for data fitting; although it does not preserve energy, it uses the same halfway vector domain as the first model. We show that this data-fitting BRDF can be used to match measured data extremely well using only a small set of parameters. We believe that this is an improvement over table-based lookups and factored versions of BRDF data.