## Non-symmetric Scattering in Light Transport Algorithms

### BibTeX

@MISC{_non-symmetricscattering,

author = {},

title = {Non-symmetric Scattering in Light Transport Algorithms},

year = {}

}

### OpenURL

### Abstract

1 Introduction The equations governing the transport and measurement of light energy can be writtenin two equivalent forms, depending on whether we solve for radiance or importance. Most current global illumination algorithms take advantage of this duality. For exam-ple, importance is often used to guide mesh refinement in finite-element approaches, and traditional ray tracing is the dual of particle tracing, which simulates the emissionand scattering of photons.

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Citation Context ...correct. For example, we show that non-symmetry occurs whenever lightis refracted, and also whenever shading normals are used (e.g. due to interpolation of normals in a triangle mesh, or bump mapping =-=[5]-=-).We examine the implications of non-symmetric scattering for light transport theory. We extend the work of Arvo et al. [4] into a complete framework for light, importance,and particle transport with ... |

124 |
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(Show Context)
Citation Context ...y algorithm that uses both lighting and viewing information, including importance-driven finite element approaches [33, 30,8], particle tracing algorithms [15, 28, 31], and bidirectional path-tracing =-=[18, 37, 38]-=-. However, we show that these problems are easy to fix. 2 Light transport with non-symmetric scattering We develop a consistent framework for light, importance, and particle transport, build-ing on th... |

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Citation Context ...that non-symmetric scattering is actuallyquite common. This can cause problems for any algorithm that uses both lighting and viewing information, including importance-driven finite element approaches =-=[33, 30,8]-=-, particle tracing algorithms [15, 28, 31], and bidirectional path-tracing [18, 37, 38]. However, we show that these problems are easy to fix. 2 Light transport with non-symmetric scattering We develo... |

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Citation Context ...adjoint. Arvo handles this with an isomorphism H between surface andfield functions, such that HG and KH are equivalent to the G and K defined above [3, p.151].6The "GRDF" described by Eric Lafortune =-=[19]-=- is simply the kernel of S. Note that S is closely relatedto the resolvent operator R* used in spectral analysis, except that R* has a parameter *, and does not havea universally accepted definition (... |

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(Show Context)
Citation Context ...yquite common. This can cause problems for any algorithm that uses both lighting and viewing information, including importance-driven finite element approaches [33, 30,8], particle tracing algorithms =-=[15, 28, 31]-=-, and bidirectional path-tracing [18, 37, 38]. However, we show that these problems are easy to fix. 2 Light transport with non-symmetric scattering We develop a consistent framework for light, import... |

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Citation Context ...neral BTDF's as well, e.g. frosted glass. 16For our purposes, the following is sufficient. Given some measure _, ffi_ is defined by the property thatR \Omegasg(x) ffi_(x \Gammasx0) d_(x) = g(x0) (see =-=[1]-=-, p.28-32).sThe (jt=ji)2 factor is not present in the adjoint, so that importance (and light particles)are not scaled when they cross the interface. Hall [14] pointed out the (jt=ji)2 scaling for radi... |

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(Show Context)
Citation Context ...that non-symmetric scattering is actuallyquite common. This can cause problems for any algorithm that uses both lighting and viewing information, including importance-driven finite element approaches =-=[33, 30,8]-=-, particle tracing algorithms [15, 28, 31], and bidirectional path-tracing [18, 37, 38]. However, we show that these problems are easy to fix. 2 Light transport with non-symmetric scattering We develo... |

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(Show Context)
Citation Context ...arameter (whose value is usually zero incomputer graphics). This has been interpreted both ways (e.g. [12], [13, p.665], [13, p.722]). In his other writings, however, Nicodemus uses r only as a label =-=[24, 23, 22]-=-. For the "distance" interpretation of r, thenotation S(! i; !r; r) for the BSSRDF is used [27, p.28]. These ambiguities can be avoided by using differenttypefaces for labels and parameters (Roman vs.... |