Bidirectional importance sampling for illumination from environment maps

Burke, David; Ghosh, Abhijeet; Heidrich, Wolfgang

doi:10.1145/1186223.1186363

Cited by 43 publications

(50 citation statements)

References 24 publications

(4 reference statements)

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“…Ultimately state-of-the-art method called Multiple Importance Sampling (MIS) [39] has made physically based rendering computationally feasible today. Particularly important for this research is the optimisation of MIS algorithms for the sampling complex materials, with custom Bidirectional Reflection Distribution Function (BRDF), and illuminated by High Dynamic Range (HDR) Images [40] [41].…”

Section: Stochastic (Monte Carlo) Based Methods -Ray Tracingmentioning

confidence: 99%

State-of-the-art review of solar design tools and methods for assessing daylighting and solar potential for building-integrated photovoltaics

Jakica

2018

Renewable and Sustainable Energy Reviews

142

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Solar design can take many different forms across disciplines with different methodologies and goals, ranging from acquiring architectural visual effects to assessing illumination for daylighting and solar radiation potential on building surfaces for PV implementation. Furthermore, a capability of solar design methodologies and tools to accurately and time efficiently simulate light phenomena can greatly influence performance results and design decisions. This is especially important in complex cases such as dense urban settings with the significant surface shadowing, and vertical facades including daylighting devices and photovoltaics. Consequently, choosing a suitable approach and tool for each design phase is essential for achieving unique design and performance goals. This paper was carried out within the framework of IEA-PVPS Task 15 -BIPV and it aims to facilitate this decision for all parties involved in solar design process. Here presented, is an overview of almost 200 solar design tools, analyzing their numerous features regarding accuracy, complexity, scale, computation speed, representation as well as building design process integration in about 50 2D/3D, CAD/CAM and BIM software environments. Furthermore, tools from various fields have been analysed in a broad interdisciplinary context of solar design with a particular attention for being used for Daylighting and Building-Integrated Photovoltaics (BIPV) purposes. This approach should open many new perspectives on a potentially wider multidisciplinary usage and interpretation of solar design tools, sometimes well beyond their initial scope of work.

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Section: Stochastic (Monte Carlo) Based Methods -Ray Tracingmentioning

confidence: 99%

State-of-the-art review of solar design tools and methods for assessing daylighting and solar potential for building-integrated photovoltaics

Jakica

2018

Renewable and Sustainable Energy Reviews

142

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“…A common approach to decreasing the distribution construction cost is to exclude visibility from it [BGH05,CJAMJ05]. Unfortunately, as Figure 1 demonstrates, doing so in occluded scenes can destroy proportionality and lead to dramatic variance increase.…”

Section: Algorithm Overviewmentioning

confidence: 99%

“…Ideally, this PDF would be the product of the individual terms under the reflection integral. In practice, not all of these terms are known, so the PDF often includes only some of them, visibility in particular being commonly omitted [CJAMJ05,BGH05,WA09]. Moreover, most importance sampling methods do not take advantage of the fact that illumination is often piece-wise smooth over surfaces, and build a PDF for each shading point independently, which can be too expensive.…”

Section: Introductionmentioning

confidence: 99%

Importance Caching for Complex Illumination

Georgiev

Křivánek

Popov

et al. 2012

Computer Graphics Forum

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Realistic rendering requires computing the global illumination in the scene, and Monte Carlo integration is the best-known method for doing that. The key to good performance is to carefully select the costly integration samples, which is usually achieved via importance sampling. Unfortunately, visibility is difficult to factor into the importance distribution, which can greatly increase variance in highly occluded scenes with complex illumination. In this paper, we present importance caching -a novel approach that selects those samples with a distribution that includes visibility, while maintaining efficiency by exploiting illumination smoothness. At a sparse set of locations in the scene, we construct and cache several types of probability distributions with respect to a set of virtual point lights (VPLs), which notably include visibility. Each distribution type is optimized for a specific lighting condition. For every shading point, we then borrow the distributions from nearby cached locations and use them for VPL sampling, avoiding additional bias. A novel multiple importance sampling framework finally combines the many estimators. In highly occluded scenes, where visibility is a major source of variance in the incident radiance, our approach can reduce variance by more than an order of magnitude. Even in such complex scenes we can obtain accurate and low noise previews with full global illumination in a couple of seconds on a single mid-range CPU.

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“…Some methods include the surface BRDF [6,8,7] in the importance function. This allows efficient sampling of a combination of high frequency illumination and glossy surfaces with a large specular component.…”

Section: Related Workmentioning

confidence: 99%

“…We define the function J j (p 0 , p 1 ) in each triangle ( j) with vertices A, B and C as a linear combination of products of illumination and the clamped cosines at vertices. The integral of the Jacobian (see Equation (6)) within each triangle is simply the volume of the truncated triangular prism defined by the triangle. Given that the Jacobian varies linearly within each triangle ( j), we can write G j as a(n), W j where…”

Section: Steerable Weightingmentioning

confidence: 99%

Steerable Importance Sampling

Subr

Arvo

2007

2007 IEEE Symposium on Interactive Ray Tracing

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We present an algorithm for efficient stratified importance sampling of environment maps that generates samples in the positive hemisphere defined by local orientation of arbitrary surfaces while accounting for cosine weighting. The importance function is dynamically adjusted according to the surface normal using steerable basis functions. The algorithm is easy to implement and requires no user-defined parameters. As a preprocessing step, we approximate the incident illumination from an environment map as a continuous piecewise linear function on S 2 and represent this as a triangulated height field. The product of this approximation and a dynamically orientable steering function, viz. the cosine lobe, serves as an importance sampling function. Our method allows the importance function to be sampled with an asymptotic cost of O(logn) per sample where n is the number of triangles. The most novel aspect of the algorithm is its ability to dynamically compute normalization factors which are integrals of the illumination over the positive hemispheres defined by the local surface normals during shading. The key to this feature is that the weight variation of each triangle due to the clamped cosine steering function can be well approximated by a small number of spherical harmonic coefficients which can be accumulated over any collection of triangles, in any orientation, without introducing higher-order terms. Consequently, the weighted integral of the entire steerable piecewise-linear approximation is no more costly to compute than that of a single triangle, which makes re-weighting and re-normalizing with respect to any surface orientation a trivial constant-time operation. The choice of spherical harmonics as the set of basis functions for our steerable importance function allows for easy rotation between coordinate systems. Another novel element of our algorithm is an analytic parametrization for generating stratified samples with linearly-varying density over a triangular support.

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Bidirectional importance sampling for illumination from environment maps

Abstract: We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA

Cited by 43 publications

References 24 publications

State-of-the-art review of solar design tools and methods for assessing daylighting and solar potential for building-integrated photovoltaics

State-of-the-art review of solar design tools and methods for assessing daylighting and solar potential for building-integrated photovoltaics

Importance Caching for Complex Illumination

Steerable Importance Sampling

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