This paper addresses light transport through a discrete random medium, which we define as a volume filled with macroscopic scattering geometry generated by a random process. This formulation is more general than stand...
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In this paper we introduce Functional Difference Predictors (FDPs), a new class of perceptually-based image difference metrics that predict how image errors affect the ability to perform visual tasks using the images....
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In this paper we introduce Functional Difference Predictors (FDPs), a new class of perceptually-based image difference metrics that predict how image errors affect the ability to perform visual tasks using the images. To define the properties of FDPs, we conduct a psychophysical experiment that focuses on two visual tasks: spatial layout and material estimation. In the experiment we introduce errors in the positions and contrasts of objects reflected in glossy surfaces and ask subjects to make layout and material judgments. The results indicate that layout estimation depends only on positional errors in the reflections and material estimation depends only on contrast errors. These results suggest that in many task contexts, large visible image errors may be tolerated without loss in task performance, and that FDPs may be better predictors of the relationship between errors and performance than current Visible Difference Predictors (VDPs).
We present an experimental study of the angular distribution of light scattered from several rough metallic surfaces, which cover a range of roughness conditions. The substrate materials are steel or glass;roughened b...
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We present an experimental study of the angular distribution of light scattered from several rough metallic surfaces, which cover a range of roughness conditions. The substrate materials are steel or glass;roughened by bead-blasting, grinding, or etching;and aluminum-coated. The measured surface-roughness statistics are filtered by using a composite roughness model. The raw mechanical roughnesses range from 0.21/μm to 2.66/ μum;the high-frequency small-scale roughnesses range from 0.13/μm to 0.86μm. The optical wavelength is 550nm, so that the roughness-to-wavelength ratio is of order one. A BRDF model based on the Kirchhoff approximation is used to establish a relationship between surface-height statistics and the angular distribution of the scattered light. Angular distributions calculated with the BRDF model are fit to the measurements. The best-fit roughness statistics from the BRDF model agree closely with those measured for the high-frequency small-scale roughness component. The latter roughness component, which has the highest surface slopes, is thus the primary contributor to the angular distribution of the reflected light. We show that the Kirchhoff approximation can be applied to rough metallic surfaces that have multiple scales of roughness and near-, but not perfect, Gaussian surface-height distributions.
Previous work in the hidden-surface problem has revealed two key concepts. First, the removal of nonvisible surfaces is essentially a sorting problem. Second, some form of coherence is essential for the efficient solu...
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A method for analytically calculating the forces between systems of rigid bodies in resting (non-colliding) contact is presented. The systems of bodies may either be in motion or static equilibrium and adjacent bodies...
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ISBN:
(纸本)0897913124
A method for analytically calculating the forces between systems of rigid bodies in resting (non-colliding) contact is presented. The systems of bodies may either be in motion or static equilibrium and adjacent bodies may touch at multiple points. The analytic formulation of the forces between bodies in non-colliding contact can be modified to deal with colliding bodies. Accordingly, an improved method for analytically calculating the forces between systems of rigid bodies in colliding contact is also presented. Both methods can be applied to systems with arbitrary holonomic geometric constraints, such as linked figures. The analytical formulations used treat both holonomic and non-holonomic constraints in a consistent manner.
Algorithms and computational complexity measures for simulating the motion of contacting bodies with friction are presented. The bodies are restricted to be perfectly rigid bodies that contact at finitely many points....
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An algorithm for determining visible lines or visible surfaces in polygonal form, at object resolution, is presented. The original scene must consist of non-intersecting planar polygons. The procedure relies on image ...
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Perceptually uniform color spaces can be a useful tool for solving computergraphics color selection problems. However, before they can be used effectively some basic principles of tristimulus colorimetry must be unde...
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ISBN:
(纸本)0897910214
Perceptually uniform color spaces can be a useful tool for solving computergraphics color selection problems. However, before they can be used effectively some basic principles of tristimulus colorimetry must be understood and the color reproduction device on which they are to be used must be properly adjusted. The Munsell Book of Color and the Optical Society of America (OSA) Uniform Color Scale are two uniform color spaces which provide a useful way of organizing the colors of a digitally controlled color television monitor. The perceptual uniformity of these color spaces can be used to select color scales to encode the variations of parameters such as temperature or stress. � ACM. All rights reserved.
Use of the perspective projection adds important perceptual cues for image comprehension. However, it has not been widely used in volume rendering because of the lack of efficient computational algorithms and concern ...
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We describe an automated three-axis BRDF measurement instrument that can help increase the physical realism of computergraphics images by providing light scattering data for the surfaces within a synthetic scene that...
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We describe an automated three-axis BRDF measurement instrument that can help increase the physical realism of computergraphics images by providing light scattering data for the surfaces within a synthetic scene that is to be rendered. To our knowledge, the instrument is unique in combining wide angular coverage (beyond 85° from the surface normal), dense sampling of the visible wavelength spectrum (1024 samples), and rapid operation (less than ten hours for complete measurement of an isotropic sample). The gonioreflectometer employs a broadband light source and a detector with a diffraction grating and linear diode array. Validation was achieved by comparisons against reference surfaces and other instruments. The accuracy and spectral and angular ranges of the BRDFs are appropriate for computergraphics imagery, while reciprocity and energy conservation are preserved. Measured BRDFs on rough aluminum, metallic silver automotive paint, and a glossy yellow paint are reported, and an example rendered automotive image is included.
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