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标题: Progressive Photon Beams [打印本页]

作者: 晃晃 时间: 2011-12-29 10:33
标题: Progressive Photon Beams
Progressive Photon Beams

Wojciech Jarosz1 Derek Nowrouzezahrai1 Robert Thomas1 Peter-Pike Sloan2 Matthias Zwicker

1Disney Research Z¨ urich 2Disney Interactive Studios 3University of Bern

Abstract

We present progressive photon beams, a new algorithm for render-

ing complex lighting in participating media. Our technique is ef-

ﬁcient, robust to complex light paths, and handles heterogeneous

media and anisotropic scattering while provably converging to the

correct solution using a bounded memory footprint. We achieve

this by extending the recent photon beams variant of volumetric

photon mapping. We show how to formulate a progressive radiance

estimate using photon beams, providing the convergence guaran-

tees and bounded memory usage of progressive photon mapping.

Progressive photon beams can robustly handle situations that are

difﬁcult for most other algorithms, such as scenes containing par-

ticipating media and specular interfaces, with realistic light sources

completely enclosed by refractive and reﬂective materials. Our

technique handles heterogeneous media and also trivially supports

stochastic effects such as depth-of-ﬁeld and glossy materials. Fi-

nally, we show how progressive photon beams can be implemented

efﬁciently on the GPU as a splatting operation, making it applicable

to interactive and real-time applications. These features make our

technique scalable, providing the same physically-based algorithm

for interactive feedback and reference-quality, unbiased solutions.

CR Categories: I.3.7 [Computer Graphics]: Three-Dimensional

Graphics and Realism—Raytracing

Keywords: participating media, global illumination, photon map-

ping, photon beams, density estimation

1 Introduction

The scattering of light creates stunning visual complexity, in par-

ticular with interactions in participating media such as clouds, fog,

and even air. Rendering this complex light transport requires solv-

ing the radiative transport equation [Chandrasekar 1960] combined

with the rendering equation [Kajiya 1986] as a boundary condition.

The gold standard for rendering is arguably computing unbiased,

noise-free images. Unfortunately, the only options to achieve this

are variants of brute force path tracing [Kajiya 1986; Lafortune and

Willems 1993; Veach and Guibas 1994; Lafortune and Willems

1996] and Metropolis light transport [Veach and Guibas 1997;

Pauly et al. 2000], which are slow to converge to noise-free images

despite recent advances [Raab et al. 2008; Yue et al. 2010]. This be-

comes particularly problematic when the scene contains so-called

SDS (specular-diffuse-specular) or SMS (specular-media-specular)

subpaths, which are actually quite common in physical scenes (e.g.

illumination due to a light source inside a glass ﬁxture). Unfor-

tunately, path tracing methods cannot robustly handle these situ-

ations, especially in the presence of small light sources. Meth-

ods based on volumetric photon mapping [Jensen and Christensen

1998; Jarosz et al. 2008] do not suffer from these problems. They

can robustly handle S(DjM)S subpaths, and generally produce less

noise. However, these methods suffer from bias, which can be elim-

inated in theory by using inﬁnitely many photons, but in practice

this is not feasible since it requires unlimited memory.

We combine the beneﬁts of these two classes of algorithms. Our ap-

proach converges to the gold standard much faster than path tracing,

is robust to S(DjM)S subpaths, and has a bounded memory foot-

print. In addition, we show how the algorithm can be accelerated on

the GPU. This allows for interactive lighting design in the presence

of complex light sources and participating media. We also obtain

reference-quality results at real-time rates for simple scenes con-

taining complex volumetric light interactions. Our algorithm grace-

fully handles a wide spectrum of ﬁdelity settings, ranging from real-

time frame rates to reference quality solutions. This makes it pos-

sible to produce interactive previews with the same technique used

for a high-quality ﬁnal render — providing visual consistency, an

essential property for interactive lighting design tools.

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作者: 菜刀吻电线 时间: 2012-3-13 23:18
不错哦,顶一下......

作者: C.R.CAN 时间: 2012-3-22 23:21
其实楼主所说的这些，俺支很少用！

作者: 晃晃 时间: 2012-3-22 23:26
不错啊　经典

作者: 菜刀吻电线 时间: 2012-3-31 23:21
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作者: 晃晃 时间: 2012-4-18 23:20
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作者: 晃晃 时间: 2012-5-2 23:22
好可爱的字,学习了

作者: C.R.CAN 时间: 2012-10-7 23:22
发了那么多，我都不知道该用哪个给你回帖了，呵呵

作者: C.R.CAN 时间: 2013-2-27 23:28
呵呵,真得不错哦!!

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