Multiple Scattering Approximation in Heterogeneous Media by Narrow Beam Distributions

Indirect illumination involving with visually rich participating media such as turbulent smoke and loud explosions contributes significantly to the appearances of other objects in a rendering scene. However, previous real‐time techniques have focused only on the appearances of the media directly visible from the viewer. Specifically, appearances that can be indirectly seen over reflective surfaces have not attracted much attention. In this paper, we present a real‐time rendering technique for such indirect views that involves the participating media. To achieve real‐time performance for computing indirect views, we leverage layered polygonal area lights (LPALs) that can be obtained by slicing the media into multiple flat layers. Using this representation, radiance entering each surface point from each slice of the volume is analytically evaluated to achieve instant calculation. The analytic solution can be derived for standard bidirectional reflectance distribution functions (BRDFs) based on the microfacet theory. Accordingly, our method is sufficiently robust to work on surfaces with arbitrary shapes and roughness values. In addition, we propose a quadrature method for more accurate rendering of scenes with dense volumes, and a transformation of the domain of volumes to simplify the calculation and implementation of the proposed method. By taking advantage of these computation techniques, the proposed method achieves real‐time rendering of indirect illumination for emissive volumes.

Section: Related Workmentioning

confidence: 99%

Real‐time Indirect Illumination of Emissive Inhomogeneous Volumes using Layered Polygonal Area Lights

Kuge

Yatagawa

Morishima

2019

“…Modeling and rendering are two main topics about cloud animation in computer graphics. Much work concerns itself with rendering participating media [YIC*10, Har05, Yus14, SDS*16]. Meanwhile, a large number of methods have also been proposed to model cloud shapes [Har05, DSY10, YLH*14, JC16].…”

Section: Related Workmentioning

confidence: 99%

Modeling Cumulus Cloud Scenes from High‐resolution Satellite Images

Zhang

Liang

Yuan

et al. 2017

Figure 1: Our physically-based method automatically reconstructs large-scale cumulus cloud scenes from high-resolution satellite images.A key aspect of our approach is to extract necessary features for modeling clouds, generating physically sound simulation results. AbstractWe present a reconstruction framework, which fits physically-based constraints to model large-scale cloud scenes from satellite images. Applications include weather phenomena visualization, flight simulation, and weather spotter training. In our method, the cloud shape is assumed to be composed of a cloud top surface and a nearly flat cloud base surface. Based on this, an effective method of multi-spectral data processing is developed to obtain relevant information for calculating the cloud base height and the cloud top height, including ground temperature, cloud top temperature and cloud shadow. A lapse rate model is proposed to formulate cloud shape as an implicit function of temperature lapse rate and cloud base temperature. After obtaining initial cloud shapes, we enrich the shapes by a fractal method and represent reconstructed clouds by a particle system. Experiment results demonstrate the capability of our method in generating physically sound large-scale cloud scenes from high-resolution satellite images.

“…We exclude some materials in which single scattering can influence appearances significantly, such as low‐concentration liquid, low‐density cloud and fog [NGD*06, KF12, SZLG10]. Observer outside : Some participating media problems consider a global effect, meaning the medium involves the entire scene, including the viewpoint or camera [SDS*16, BSA12]. In contrast, BSSRDF approaches aim only to estimate the radiance leaving the translucent object and are limited to objects that the observer cannot enter. Backlit estimation : For thick objects, the majority of light will return to the boundary where it refracts.…”

Section: Introductionmentioning

confidence: 99%

State of the Art in Efficient Translucent Material Rendering with BSSRDF

Liang,

Gao,

et al. 2023

Sub‐surface scattering is always an important feature in translucent material rendering. When light travels through optically thick media, its transport within the medium can be approximated using diffusion theory, and is appropriately described by the bidirectional scattering‐surface reflectance distribution function (BSSRDF). BSSRDF methods rely on assumptions about object geometry and light distribution in the medium, which limits their applicability to general participating media problems. However, despite the high computational cost of path tracing, BSSRDF methods are often favoured due to their suitability for real‐time applications. We review these methods and discuss the most recent breakthroughs in this field. We begin by summarizing various BSSRDF models and then implement most of them in a 2D searchlight problem to demonstrate their differences. We focus on acceleration methods using BSSRDF, which we categorize into two primary groups: pre‐computation and texture methods. Then we go through some related topics, including applications and advanced areas where BSSRDF is used, as well as problems that are sometimes important yet are ignored in sub‐surface scattering estimation. In the end of this survey, we point out remaining constraints and challenges, which may motivate future work to facilitate sub‐surface scattering.