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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenSat, 13 Apr 2024 00:51:37 +0000Particle transport and image synthesis
https://resolver.caltech.edu/CaltechAUTHORS:20160420-134938858
Authors: {'items': [{'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}, {'id': 'Kirk-David', 'name': {'family': 'Kirk', 'given': 'David'}}]}
Year: 1990
DOI: 10.1145/97880.97886
The rendering equation is similar to the linear Boltzmann
equation which has been widely studied in physics and nuclear engineering. Consequently, many of the powerful techniques which have been developed in these fields can be
applied to problems in image synthesis. In this paper we
adapt several statistical techniques commonly used in neutron transport to stochastic ray tracing and, more generally, to Monte Carlo solution of the rendering equation. First, we describe a technique known as Russian roulette which can be used to terminate the recursive tracing of rays without introducing statistical bias. We also examine the practice of creating ray trees in classical ray tracing in the light of a
well-known technique in particle transport known as splitting. We show that neither ray trees nor paths as described in [10] constitute an optimal sampling plan in themselves and that a hybrid may be more efficient.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jd7a5-67124Particle transport and image synthesis
https://resolver.caltech.edu/CaltechAUTHORS:20160420-134938603
Authors: {'items': [{'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}, {'id': 'Kirk-David', 'name': {'family': 'Kirk', 'given': 'David'}}]}
Year: 1990
DOI: 10.1145/97879.97886
The rendering equation is similar to the linear Boltzmann
equation which has been widely studied in physics and nuclear engineering. Consequently, many of the powerful techniques which have been developed in these fields can be
applied to problems in image synthesis. In this paper we
adapt several statistical techniques commonly used in neutron transport to stochastic ray tracing and, more generally, to Monte Carlo solution of the rendering equation. First, we describe a technique known as Russian roulette which can be used to terminate the recursive tracing of rays without introducing statistical bias. We also examine the practice of creating ray trees in classical ray tracing in the light of a
well-known technique in particle transport known as splitting. We show that neither ray trees nor paths as described in [10] constitute an optimal sampling plan in themselves and that a hybrid may be more efficient.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/th00w-eeg35Unbiased sampling techniques for image synthesis
https://resolver.caltech.edu/CaltechAUTHORS:20161116-153206206
Authors: {'items': [{'id': 'Kirk-David', 'name': {'family': 'Kirk', 'given': 'David'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 1991
DOI: 10.1145/127719.122735
We examine a class of adaptive sampling techniques employed in image synthesis and show that those commonly used for efficient anti-aliasing are statistically biased. This bias is dependent upon the image function being sampled as well as the strategy for determining the number of samples to use. It is most prominent in areas of high contrast and is attributable to early stages of sampling systematically favoring one extreme or the other. If the expected outcome of the entire adaptive sampling algorithm is considered, we find that the bias of the early decisions is still present in the final estimator. We propose an alternative strategy for performing adaptive sampling that is unbiased but potentially more costly. We conclude that it may not always be practical to mitigate this source of bias, but as a source of error it should be considered when high accuracy and image fidelity are a central concern.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8sntk-73q87Unbiased sampling techniques for image synthesis
https://resolver.caltech.edu/CaltechAUTHORS:20161116-152325870
Authors: {'items': [{'id': 'Kirk-David', 'name': {'family': 'Kirk', 'given': 'David'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 1991
DOI: 10.1145/122718.122735
We examine a class of adaptive sampling techniques employed in image synthesis and show that those commonly used for efficient anti-aliasing are statistically biased. This bias is dependent upon the image function being sampled as well as the strategy for determining the number of samples to use. It is most prominent in areas of high contrast and is attributable to early stages of sampling systematically favoring one extreme or the other. If the expected outcome of the entire adaptive sampling algorithm is considered, we find that the bias of the early decisions is still present in the final estimator. We propose an alternative strategy for performing adaptive sampling that is unbiased but potentially more costly. We conclude that it may not always be practical to mitigate this source of bias, but as a source of error it should be considered when high accuracy and image fidelity are a central concern.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/a1pnp-wh535A Framework for Realistic Image Synthesis
https://resolver.caltech.edu/CaltechAUTHORS:20161027-133855466
Authors: {'items': [{'id': 'Greenberg-D-P', 'name': {'family': 'Greenberg', 'given': 'Donald P.'}}, {'id': 'Torrance-K-E', 'name': {'family': 'Torrance', 'given': 'Kenneth E.'}}, {'id': 'Shirley-Peter', 'name': {'family': 'Shirley', 'given': 'Peter'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}, {'id': 'Ferwerda-J-A', 'name': {'family': 'Ferwerda', 'given': 'James A.'}}, {'id': 'Pattanaik-S', 'name': {'family': 'Pattanaik', 'given': 'Sumanta'}}, {'id': 'Lafortune-E', 'name': {'family': 'Lafortune', 'given': 'Eric'}}, {'id': 'Walter-Bruce', 'name': {'family': 'Walter', 'given': 'Bruce'}}, {'id': 'Foo-Sing-Choong', 'name': {'family': 'Foo', 'given': 'Sing-Choong'}}, {'id': 'Trumbore-Ben', 'name': {'family': 'Trumbore', 'given': 'Ben'}}]}
Year: 1997
DOI: 10.1145/258734.258914
Our goal is to develop physically based lighting models and perceptually based rendering procedures for computer graphics that will produce synthetic images that are visually and measurably indistinguishable from real-world images. Fidelity of the physical simulation is of primary concern. Our research framework is subdivided
into three sub-sections: the local light reflection model, the energy transport simulation, and the visual display algorithms. The first two subsections are physically based, and the last is perceptually based.
We emphasize the comparisons between simulations and actual
measurements, the difficulties encountered, and the need to utilize the vast amount of psychophysical research already conducted. Future research directions are enumerated. We hope that results of this research will help establish a more fundamental, scientific approach
for future rendering algorithms. This presentation describes a chronology of past research in global illumination and how parts of our
new system are currently being developed.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x661y-qc616Creating generative models from range images
https://resolver.caltech.edu/CaltechAUTHORS:20161212-170904309
Authors: {'items': [{'id': 'Ramamoorthi-Ravi', 'name': {'family': 'Ramamoorthi', 'given': 'Ravi'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 1999
DOI: 10.1145/311535.311557
We describe a new approach for creating concise high-level generative models from range images or other approximate representations of real objects. Using data from a variety of acquisition techniques and a user-defined class of models, our method produces a compact object representation that is intuitive and easy to edit. The algorithm has two inter-related phases: recognition, which chooses
an appropriate model within a user-specified hierarchy, and
parameter estimation, which adjusts the model to best fit the data. Since the approach is model-based, it is relatively insensitive to noise and missing data. We describe practical heuristics for automatically making tradeoffs between simplicity and accuracy to select the best model in a given hierarchy. We also describe a general and efficient technique for optimizing a model by refining its constituent curves. We demonstrate our approach for model recovery using both real and synthetic data and several generative model hierarchies.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/yb316-t0v07Perturbation methods for interactive specular reflections
https://resolver.caltech.edu/CaltechAUTHORS:20170408-171427414
Authors: {'items': [{'id': 'Chen-Min', 'name': {'family': 'Chen', 'given': 'Min'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 2000
DOI: 10.1109/2945.879786
We describe an approach for interactively approximating specular reflections in arbitrary curved surfaces. The technique is applicable to any smooth implicitly defined reflecting surface that is equipped with a ray intersection procedure; it is also extremely efficient as it employs local perturbations to interpolate point samples analytically. After ray tracing a sparse set of reflection paths with respect to a given vantage point and static reflecting surfaces, the algorithm rapidly approximates reflections of arbitrary points in 3-space by expressing them as perturbations of nearby points with known reflections. The reflection of each new point is approximated to second-order accuracy by applying a closed-form perturbation formula to one or more nearby reflection paths. This formula is derived from the Taylor expansion of a reflection path and is based on first and second-order path derivatives. After preprocessing, the approach is fast enough to compute reflections of tessellated diffuse objects in arbitrary curved surfaces at interactive rates using standard graphics hardware. The resulting images are nearly indistinguishable from ray traced images that take several orders of magnitude longer to generate.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/p4qew-app65Theory and Application of Specular Path Perturbation
https://resolver.caltech.edu/CaltechAUTHORS:20160822-152504191
Authors: {'items': [{'id': 'Chen-Min', 'name': {'family': 'Chen', 'given': 'Min'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 2000
DOI: 10.1145/380666.380670
In this paper we apply perturbation methods to the problem of computing specular reflections in curved surfaces. The key idea is to generate families of closely related optical paths by expanding a given path into a high-dimensional Taylor series. Our path perturbation method is based on closed-form expressions for linear and higher-order approximations of ray paths, which are derived using Fermat's Variation Principle and the Implicit Function Theorem (IFT). The perturbation formula presented here holds for general multiple-bounce reflection
paths and provides a mathematical foundation for exploiting path coherence in ray tracing acceleration techniques and incremental rendering. To illustrate its use, we describe an
algorithm for fast approximation of specular reflections on curved surfaces; the resulting images are highly accurate and nearly indistinguishable from ray traced images.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/yet8v-akc20Fluid Sketches: Continuous Recognition and Morphing of Simple Hand-Drawn Shapes
https://resolver.caltech.edu/CaltechAUTHORS:20160420-140405722
Authors: {'items': [{'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}, {'id': 'Novins-Kevin', 'name': {'family': 'Novins', 'given': 'Kevin'}}]}
Year: 2000
DOI: 10.1145/354401.354413
We describe a new sketching interface in which shape recognition and morphing are tightly coupled. Raw input strokes are continuously morphed into ideal geometric shapes, even before the pen is lifted. By means of smooth and continual shape transformations the user is apprised of recognition progress and the appearance of the final shape, yet always retains a sense of control over the process. At each time t the system uses the trajectory traced out thus far by the pen coupled with the current appearance of the time-varying shape to classify the sketch as one of several pre-defined basic shapes. The recognition operation is performed using shape-specific fits based on least-squares or relaxation, which are continuously updated as the user draws. We describe the time-dependent transformation of the sketch, beginning with the raw pen trajectory, using a family of first-order ordinary differential
equations that depend on time and the current shape
of the sketch. Using this formalism, we describe several possible behaviors that result by varying the relative significance of new and old portions of a stroke, changing the "viscosity" of the morph, and enforcing different end conditions. A preliminary user study suggests that the new interface is particularly effective for rapidly constructing diagrams consisting of simple shapes.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7tnky-8h790Averaged Template Matching Equations
https://resolver.caltech.edu/CaltechAUTHORS:20101007-085033743
Authors: {'items': [{'id': 'Hirani-A-N', 'name': {'family': 'Hirani', 'given': 'Anil N.'}}, {'id': 'Marsden-J-E', 'name': {'family': 'Marsden', 'given': 'Jerrold E.'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 2001
DOI: 10.1007/3-540-44745-8_35
By exploiting an analogy with averaging procedures in fluid
dynamics, we present a set of averaged template matching equations.
These equations are analogs of the exact template matching equations
that retain all the geometric properties associated with the diffeomorphismgrou
p, and which are expected to average out small scale features
and so should, as in hydrodynamics, be more computationally efficient
for resolving the larger scale features. Froma geometric point of view,
the new equations may be viewed as coming from a change in norm that
is used to measure the distance between images. The results in this paper
represent first steps in a longer termpro gram: what is here is only
for binary images and an algorithm for numerical computation is not
yet operational. Some suggestions for further steps to develop the results
given in this paper are suggested.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/01hkj-34e13Closed-Form Expressions for Irradiance from Non-Uniform Lambertian Luminaires Part II: Polynomially-Varying Radiant Exitance
https://resolver.caltech.edu/CaltechCSTR:2000.cs-tr-00-04
Authors: {'items': [{'id': 'Chen-Min', 'name': {'family': 'Chen', 'given': 'Min'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 2001
DOI: 10.7907/Z9XG9P5B
We present new analytical techniques for computing illumination from non-uniform luminaires. The methods are based on new closed-form expressions derived by generalizing the concepts of irradiance tensor and angular moment to rational forms and an arbitrary number of directions, known as rational irradiance tensors and rational angular moments, respectively. The techniques apply to any emission, reflection or transmission distribution expressed as a polynomial over a polygonal surface, and provide a powerful mathematical tool to handle more complex BRDF's. We derive closed-form expressions for irradiance due to polygonal luminaires with polynomially varying radiant exitance, which satisfy a recurrence relation that subsumes Lambert's formula for uniform luminaires. Our formulas extend the class of available closed-form expressions for computing direct radiative transfer from planar surfaces to points, and can find many potential applications in simulating non-Lambertian illumination and scattering phenomenahttps://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/epsbd-9q996Closed-Form Expressions for Irradiance from Non-Uniform Lambertian Luminaires Part I: Linearly-Varying Radiant Exitance
https://resolver.caltech.edu/CaltechCSTR:2000.cs-tr-00-01
Authors: {'items': [{'id': 'Chen-Min', 'name': {'family': 'Chen', 'given': 'Min'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}]}
Year: 2001
DOI: 10.7907/Z92805MQ
We present a closed-form expression for the irradiance at a point on a surface due to an arbitrary polygonal Lambertian lurninaire with linearly-varying radiant exitance. The solution consists of elementary functions and a single well-behaved special function that can be either approximated directly or computed exactly in terms of classical special functions such as Clausen's integral or the closely related dilogarithm. We first provide a general boundary integral that applies to all planar luminaires and then derive the closed-form expression that applies to arbitrary polygons, which is the result most relevant for global illumination. Our approach is to express the problem as an integral of a simple class of rational functions over regions of the sphere, and to convert the surface integral to a boundary integral using a generalization of irradiance tensors. The result extends the class of available closed-form expressions for computing direct radiative transfer from finite areas to differential areas. We provide an outline of the derivation, a detailed proof of the resulting formula, and complete pseudo-code of the resulting algorithm. Finally, we demonstrate the validity of our algorithm by comparison with Monte Carlo. While there are direct applications of this work, it is primarily of theoretical interest as it introduces much of the machinery needed to derive closed-form solutions for the general case of luminaires with radiance distributions that vary polynomially in both position and direction.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/n5cvt-77741Geometric anticipation: assisting users in 2D layout tasks
https://resolver.caltech.edu/CaltechAUTHORS:20161220-151809855
Authors: {'items': [{'id': 'Stumpfel-Jessi', 'name': {'family': 'Stumpfel', 'given': 'Jessi'}}, {'id': 'Arvo-J-R', 'name': {'family': 'Arvo', 'given': 'James'}}, {'id': 'Novins-Kevin', 'name': {'family': 'Novins', 'given': 'Kevin'}}]}
Year: 2006
DOI: 10.1145/1111449.1111532
We describe an experimental interface that anticipates a user's intentions and accommodates predicted changes in advance. Our canonical example is an interactive version of ``magnetic poetry'' in which rectangular blocks containing single words can be juxtaposed to form arbitrary sentences or ``poetry.'' The user can rearrange the blocks at will, forming and dissociating word sequences. A crucial attribute of the blocks in our system is that they anticipate insertions and gracefully rearrange themselves in time to make space for a new word or phrase. The challenges in creating such an interface are three fold: 1) the user's intentions must be inferred from noisy input, 2) arrangements must be altered smoothly and intuitively in response to anticipated changes, and 3) new and changing goals must be handled gracefully at any time, even in mid animation. We describe a general approach for handling the dynamic creation and deletion of organizational goals. Fluid motion is achieved by continually applying and correcting goal-directed forces to the objects. Future applications of this idea include the manipulation of text and graphical elements within documents and the manipulation of symbolic information such as equations.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/we23b-y0760