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 bei...
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作者：
BECKMAN, BComputer Graphics Laboratory
Information Systems Engineering Section Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive Pasadena CA 91109 U.S.A.
Programming environments for interactive graphics software typically have a multiplicity of tools and applications. Many of these programs contain ad hoc 'little language' interpreters1 that do many similar th...
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Programming environments for interactive graphics software typically have a multiplicity of tools and applications. Many of these programs contain ad hoc 'little language' interpreters1 that do many similar things in needlessly different ways. In particular, many little languages have, in addition to their special-purpose constructs, vestigial support for ordinary programming, such as variables, loops and conditionals. If a single, standard programming language were the basis for all these little languages, they could have complete, coherent programming semantics;they could communicate with each other more easily;no design work for basic constructs would be needed;and interpreter implementation work would be saved. The approach of reusing and extending the same core language and interpreter for a variety of little languages is the extension language approach. Scheme is proposed as a good choice for such a core language. Scheme is a simple, elegant, high-level programming language. Extendable implementations are readily available in C source form. Example applications in Scheme from interactive graphics are presented that would be nearly impossible to code in a typical scripting language and very tedious to code in a lower-level implementation language such as C.
The Healthy Cities Project is an initiative of the European Office of the World Health Organization. The aims of this project are to move health high on the agenda for city policy makers and planners and to better int...
The independent calculation of local position and orientation of the Lambertian surface of an opaque object is proposed using the photometric stereo method. A number of shaded video images are taken using different po...
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The independent calculation of local position and orientation of the Lambertian surface of an opaque object is proposed using the photometric stereo method. A number of shaded video images are taken using different positions of an ideal point light source which is placed close to the object. Normally, three images are required for a uniform and four for a textured Lambertian surface. By restricting three light sources to lie in a straight line, the depth calculations for an arbitrary surface with textured Lambertian reflection characteristics can be also determined; however, in this case the orientation of the surface cannot be calculated independently. It is shown that for both uniform and textured Lambertian surfaces the equations which are functions of three independent variables, namely, depth ( D ) and surface normal direction vector (n = [ p , q , − 1]), can be reduced to a single nonlinear equation of depth, i.e., the distance between the camera and the point on the surface. Both convergence and a unique solution are ensured because of the simple behavior of the nonlinear equation within a practical range of depth and gradient values. The robustness of the algorithm is demonstrated by synthetic as well as experimental data. The calculation of the approximate positions and orientations of discontinuous surfaces is demonstrated when random noise is added to the synthetically calculated image intensities. Two parallel planes with a gap, two sloped planes, and a spherical surface are used to demonstrate that the algorithms work well. An important feature of calculating both depth and orientation independently is that for smooth surfaces they must obey the partial differential expressions p = δ D δ x and q = δ D δ y . If we are certain that the experimental errors are within a known limit then the numerical approximation to these partial derivative expressions can be used to determine discontinuities within the image. On the other hand, if we know that the surface
Two experiments were performed to rank different types of display formats common to CAD applications in terms of geometric information conveyed and perceived realism of objects. Display types tested were: wireframe, w...
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We use constrained optimization to select operating parameters for two circuits: a simple 3-transistor square root circuit, and an analog VLSI artificial cochlea. This automated method uses computer controlled measure...
ISBN:
(纸本)9781558602229
We use constrained optimization to select operating parameters for two circuits: a simple 3-transistor square root circuit, and an analog VLSI artificial cochlea. This automated method uses computer controlled measurement and test equipment to choose chip parameters which minimize the difference between the actual circuit's behavior and a specified goal behavior. Choosing the proper circuit parameters is important to compensate for manufacturing deviations or adjust circuit performance within a certain range. As biologically-motivated analog VLSI circuits become increasingly complex, implying more parameters, setting these parameters by hand will become more cumbersome. Thus an automated parameter setting method can be of great value [Fleischer 90]. Automated parameter setting is an integral part of a goal-based engineering design methodology in which circuits are constructed with parameters enabling a wide range of behaviors, and are then "tuned" to the desired behaviors automatically.
Summary form only give. Teleological modeling, a developing approach for creating abstractions and mathematical representations of physically realistic time-dependent objects, is described. In this approach, geometric...
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Summary form only give. Teleological modeling, a developing approach for creating abstractions and mathematical representations of physically realistic time-dependent objects, is described. In this approach, geometric constraint-properties, mechanical properties of objects, the parameters representing an object, and the control of the object are incorporated into a single conceptual framework. A teleological model incorporates time-dependent goals of behavior of purpose as the primary abstraction and representation of what the object is. A teleological implementation takes a geometrically incomplete specification of the motion, position, and shape of an object, and produces a geometrically complete description of the object's shape and behavior as a function of time. Teleological modeling techniques may be suitable for consideration in computer vision algorithms by extending the current notions about how to make mathematical representations of objects. Teleological descriptions can produce compact representations for many of the physically derivable quantities controlling the shapes, combining-operations, and constraints which govern the formation and motion of objects.< >
Considers the application of connectionist algorithms to pattern synthesis. The emphasis is on general pattern synthesis approaches which may be tailored to model arbitrary phenomena to some degree of accuracy. One pa...
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Considers the application of connectionist algorithms to pattern synthesis. The emphasis is on general pattern synthesis approaches which may be tailored to model arbitrary phenomena to some degree of accuracy. One pattern synthesis task is to create novel samples of a given class of patterns, where class membership is specified by example rather than by rule. A recently introduced paradigm, termed creation by refinement (CBR), accomplishes this task. The CBR paradigm employs a standard neural net which has been trained to recognize the desired class of patterns. CBR probabilistically explores the pseudouniverse of the function learned by this critic net. The author considers several pattern synthesis approaches based on CBR. A variation of CBR based on a competitive learning algorithm is introduced.< >
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