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57
Lightcuts: a scalable approach to illumination
 ACM Transactions on Graphics (Proc. SIGGRAPH
, 2005
"... Lightcuts is a scalable framework for computing realistic illumination. It handles arbitrary geometry, nondiffuse materials, and illumination from a wide variety of sources including point lights, area lights, HDR environment maps, sun/sky models, and indirect illumination. At its core is a new alg ..."
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Cited by 107 (17 self)
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Lightcuts is a scalable framework for computing realistic illumination. It handles arbitrary geometry, nondiffuse materials, and illumination from a wide variety of sources including point lights, area lights, HDR environment maps, sun/sky models, and indirect illumination. At its core is a new algorithm for accurately approximating illumination from many point lights with a strongly sublinear cost. We show how a group of lights can be cheaply approximated while bounding the maximum approximation error. A binary light tree and perceptual metric are then used to adaptively partition the lights into groups to control the error vs. cost tradeoff. We also introduce reconstruction cuts that exploit spatial coherence to accelerate the generation of antialiased images with complex illumination. Results are demonstrated for five complex scenes and show that lightcuts can accurately approximate hundreds of thousands of point lights using only a few hundred shadow rays. Reconstruction cuts can reduce the number of shadow rays to tens.
Imperfect shadow maps for efficient computation of indirect illumination
 ACM Trans. Graph. (Proc. SIGGRAPH Asia
"... GTX. The scene is illuminated with a small spot light (upper right); all other illumination and shadowing is indirect (one bounce). We present a method for interactive computation of indirect illumination in large and fully dynamic scenes based on approximate visibility queries. While the highfrequ ..."
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Cited by 65 (15 self)
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GTX. The scene is illuminated with a small spot light (upper right); all other illumination and shadowing is indirect (one bounce). We present a method for interactive computation of indirect illumination in large and fully dynamic scenes based on approximate visibility queries. While the highfrequency nature of direct lighting requires accurate visibility, indirect illumination mostly consists of smooth gradations, which tend to mask errors due to incorrect visibility. We exploit this by approximating visibility for indirect illumination with imperfect shadow maps—lowresolution shadow maps rendered from a crude pointbased representation of the scene. These are used in conjunction with a global illumination algorithm based on virtual point lights enabling indirect illumination of dynamic scenes at realtime frame rates. We demonstrate that imperfect shadow maps are a valid approximation to visibility, which makes the simulation of global illumination an order of magnitude faster than using accurate visibility.
Dynamic ambient occlusion and indirect lighting
 GPU Gems
"... In this chapter we describe a new technique for computing diffuse light transfer and show how it can be used to compute global illumination for animated scenes. Our technique is efficient enough when implemented on a fast GPU to calculate ambient occlusion and indirect lighting data on the fly for e ..."
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Cited by 59 (0 self)
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In this chapter we describe a new technique for computing diffuse light transfer and show how it can be used to compute global illumination for animated scenes. Our technique is efficient enough when implemented on a fast GPU to calculate ambient occlusion and indirect lighting data on the fly for each rendered frame. It does not have the limitations of precomputed radiance transfer (PRT) or precomputed ambient occlusion techniques, which are limited to rigid objects that do not move relative to one another (Sloan 2002). Figure 141 illustrates how ambient occlusion and indirect lighting enhance environment lighting. Our technique works by treating polygon meshes as a set of surface elements that can emit, transmit, or reflect light and that can shadow each other. This method is so efficient because it works without calculating the visibility of one element to another. Instead, it uses a much simpler and faster technique based on approximate shadowing to account for occluding (blocking) geometry. 14.1 Surface Elements The first step in our algorithm is to convert the polygonal data to surface elements to make it easy to calculate how much one part of a surface shadows or illuminates another. Figure 142 illustrates the basic concept. We define a surface element as an oriented disk with a position, normal, and area. An element has a front face and a back 214_gems2_ch14_new.qxp 2/2/2005 4:10 PM Page 223 224 face. Light is emitted and reflected from the frontfacing side. Light is transmitted and shadows are cast from the back. We create one element per vertex of the mesh. Assuming that the vertices are defined with a position and normal already, we just need to calculate the area of each element. We calculate the area at a vertex as the sum of onethird of the area of the triangles that share the vertex (or onefourth of the area for quads). Heron’s formula for the area of a triangle with sides of length a, b, and c is:
The irregular Zbuffer: Hardware acceleration for irregular data structures
, 2005
"... The classical Zbuffer visibility algorithm samples a scene at regularly spaced points on an image plane. Previously, we introduced an extension of this algorithm called the irregular Zbuffer that permits sampling of the scene from arbitrary points on the image plane. These sample points are stored ..."
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Cited by 29 (3 self)
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The classical Zbuffer visibility algorithm samples a scene at regularly spaced points on an image plane. Previously, we introduced an extension of this algorithm called the irregular Zbuffer that permits sampling of the scene from arbitrary points on the image plane. These sample points are stored in a twodimensional spatial data structure. Here we present a set of architectural enhancements to the classical Zbuffer acceleration hardware which supports efficient execution of the irregular Zbuffer. These enhancements enable efficient parallel construction and query of certain irregular data structures, including the grid of linked lists used by our algorithm. The enhancements include flexible atomic readmodifywrite units located near the memory controller, an internal routing network between these units and the fragment processors, and a MIMD fragment processor design. We simulate the performance of this new architecture and demonstrate that it can be used to render highquality shadows in geometrically complex scenes at interactive frame rates. We also discuss other uses of the irregular Zbuffer algorithm and the implications of our architectural changes in the design of chipmultiprocessors.
Interactive relighting with dynamic BRDFs
, 2007
"... We present a technique for interactive relighting in which source radiance, viewing direction, and BRDFs can all be changed on the fly. In handling dynamic BRDFs, our method efficiently accounts for the effects of BRDF modification on the reflectance and incident radiance at a surface point. For re ..."
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Cited by 27 (2 self)
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We present a technique for interactive relighting in which source radiance, viewing direction, and BRDFs can all be changed on the fly. In handling dynamic BRDFs, our method efficiently accounts for the effects of BRDF modification on the reflectance and incident radiance at a surface point. For reflectance, we develop a BRDF tensor representation that can be factorized into adjustable terms for lighting, viewing, and BRDF parameters. For incident radiance, there exists a nonlinear relationship between indirect lighting and BRDFs in a scene, which makes linear light transport frameworks such as PRT unsuitable. To overcome this problem, we introduce precomputed transfer tensors (PTTs) which decompose indirect lighting into precomputable components that are each a function of BRDFs in the scene, and can be rapidly combined at run time to correctly determine incident radiance. We additionally describe a method for efficient handling of highfrequency specular reflections by separating them from the BRDF tensor representation and processing them using precomputed visibility information. With relighting based on PTTs, interactive performance with indirect lighting is demonstrated in applications to BRDF animation and material tuning.
Razor: An Architecture for Dynamic Multiresolution Ray Tracing
, 2006
"... Rendering systems organized around the ray tracing visibility algorithm provide a powerful and general tool for generating realistic images. These systems are being rapidly adopted for offline rendering tasks, and there is increasing interest in utilizing ray tracing for interactive rendering as wel ..."
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Cited by 22 (3 self)
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Rendering systems organized around the ray tracing visibility algorithm provide a powerful and general tool for generating realistic images. These systems are being rapidly adopted for offline rendering tasks, and there is increasing interest in utilizing ray tracing for interactive rendering as well. Unfortunately, standard ray tracing systems suffer from several fundamental problems that limit their flexibility and performance, and until these issues are addressed ray tracing will have no hope of replacing Zbuffer systems for most interactive graphics applications. To realize the full potential of ray tracing, it is necessary to use variants such as distribution ray tracing and path tracing that can compute compelling visual effects: soft shadows, glossy reflections, ambient occlusion, and many others. Unfortunately, current distribution ray tracing systems are fundamentally inefficient. They have high overhead for rendering dynamic scenes, use excessively detailed geometry for secondary rays, perform redundant computations for shading and secondary rays, and have irregular data access and computation patterns that are a poor match for costeffective hardware. We describe Razor, a new software architecture for a distribution ray tracer that addresses these issues. Razor supports watertight multiresolution geometry using a novel interpolation technique and a multiresolution kDtree acceleration structure built ondemand each frame from a tightly integrated application scene graph. This dramatically reduces the cost of supporting dynamic scenes and improves data access and computation patterns for secondary rays. The architecture also decouples shading computations from visibility computations using a twophase shading scheme. It uses existing bestpractice techniques including bundling rays into SIMD packets for efficient computation and memory access. We present an experimental system that implements these techniques, although not in real time. We present results from this system demonstrating the effectiveness of its software architecture and algorithms.
Interactive Indirect Illumination Using VoxelBased Cone Tracing: An Insight
"... Figure 1: Realtime indirect illumination (2570 fps on a GTX480): Our approach supports diffuse and glossy light bounces on complex scenes. We rely on a voxelbased hierarchical structure to ensure efficient integration of 2bounce illumination. (Right scene courtesy of G. M. Leal Llaguno) ..."
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Cited by 21 (1 self)
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Figure 1: Realtime indirect illumination (2570 fps on a GTX480): Our approach supports diffuse and glossy light bounces on complex scenes. We rely on a voxelbased hierarchical structure to ensure efficient integration of 2bounce illumination. (Right scene courtesy of G. M. Leal Llaguno)
The automatic interactive lighting preview system
 ACM Trans. Graph. (Proc. SIGGRAPH
, 2007
"... ■End of pipeline fixed geometry, viewpoint, material ■Slow feedback 1060 mins to renderLighting Design another 1 hour later... ■End of pipeline fixed geometry, viewpoint, material ■Slow feedback 1060 mins to renderGoal: Fast Lighting Preview Exploit redundancy between previews ■ geometry ■ view ■ ..."
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Cited by 20 (1 self)
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■End of pipeline fixed geometry, viewpoint, material ■Slow feedback 1060 mins to renderLighting Design another 1 hour later... ■End of pipeline fixed geometry, viewpoint, material ■Slow feedback 1060 mins to renderGoal: Fast Lighting Preview Exploit redundancy between previews ■ geometry ■ view ■ materialHighLevel Approach ■ Precompute deepframebuffer cache e.g. normal position diffuse texture specular texture ■ Preview dynamically on GPU as the user specifies new light parametersPrior WorkRender Caching
Perceptual influence of approximate visibility in indirect illumination
 ACM Trans. Appl. Percept
, 2009
"... Figure 1: Renderings of the arches scene, where the indirect illumination in each image is computed with a different visibility approximation. Our psychophysical study shows that many of these visibility approximations produce images that are perceptually very similar to reference renderings (cf. Fi ..."
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Cited by 13 (5 self)
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Figure 1: Renderings of the arches scene, where the indirect illumination in each image is computed with a different visibility approximation. Our psychophysical study shows that many of these visibility approximations produce images that are perceptually very similar to reference renderings (cf. Fig. 3). In this paper we evaluate the use of approximate visibility for efficient global illumination. Traditionally, accurate visibility is used in light transport. However, the indirect illumination we perceive on a daily basis is rarely of high frequency nature, as the most significant aspect of light transport in realworld scenes is diffuse, and thus displays a smooth gradation. This raises the question of whether accurate visibility is perceptually necessary in this case. To answer this question, we conduct a psychophysical study on the perceptual influence of approximate visibility on indirect illumination. This study reveals that accurate visibility is not required and that certain approximations may be introduced.
Fast Final Gathering via Reverse Photon Mapping
, 2005
"... We present a new algorithm for computing indirect illumination based on density estimation similarly to photon mapping. We accelerate the search for final gathering by reorganizing the computation in the reverse order. We use two trees that organize spatially not only the position of photons but a ..."
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Cited by 12 (3 self)
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We present a new algorithm for computing indirect illumination based on density estimation similarly to photon mapping. We accelerate the search for final gathering by reorganizing the computation in the reverse order. We use two trees that organize spatially not only the position of photons but also the position of final gather rays. The achieved