Millions of people worldwide need glasses or contact lenses to see or read properly. We introduce a computational display technology that predistorts the presented content for an observer, so that the target image is perceived without the need for eyewear. By designing optics in concert with prefiltering algorithms, the proposed display architecture achieves significantly higher resolution and contrast than prior approaches to vision-correcting image display. We demonstrate that inexpensive light field displays driven by efficient implementations of 4D prefiltering algorithms can produce the desired vision-corrected imagery, even for higher-order aberrations that are difficult to be corrected with glasses. The proposed computational display architecture is evaluated in simulation and with a low-cost prototype device.

In this article, we propose a novel personalized ranking system for amateur photographs. The proposed framework treats the photograph assessment as a ranking problem and we introduce the idea of personalized ranking , which ranks photographs considering both their aesthetic qualities and personal preferences. Photographs are described using three types of features: photo composition , color and intensity distribution , and personalized features . An aesthetic prediction model is learned from labeled photographs by using the proposed image features and RBF-ListNet learning algorithm. The experimental results show that the proposed framework outperforms in the ranking performance: a Kendall's tau value of 0.432 is significantly higher than those obtained by the features proposed in one of the state-of-the-art approaches (0.365) and by learning based on support vector regression (0.384). To realize personalization in ranking, three approaches are proposed: the feature-based approach allows users to select photographs with specific rules, the example-based approach takes the positive feedback from users to rerank the photograph, and the list-based approach takes both positive and negative feedback from users into consideration. User studies indicate that all three approaches are effective in both aesthetic and personalized ranking.

Optical aberrations of the human eye are currently corrected using eyeglasses, contact lenses, or surgery. We describe a fourth option: modifying the composition of displayed content such that the perceived image appears in focus, after passing through an eye with known optical defects. Prior approaches synthesize pre-filtered images by deconvolving the content by the point spread function of the aberrated eye. Such methods have not led to practical applications, due to severely reduced contrast and ringing artifacts. We address these limitations by introducing multilayer pre-filtering, implemented using stacks of semi-transparent, light-emitting layers. By optimizing the layer positions and the partition of spatial frequencies between layers, contrast is improved and ringing artifacts are eliminated. We assess design constraints for multilayer displays; autostereoscopic light field displays are identified as a preferred, thin form factor architecture, allowing synthetic layers to be displaced in response to viewer movement and refractive errors. We assess the benefits of multilayer pre-filtering versus prior light field pre-distortion methods, showing pre-filtering works within the constraints of current display resolutions. We conclude by analyzing benefits and limitations using a prototype multilayer LCD.

In this paper, we propose a novel personalized ranking system for amateur photographs. Although some of the features used in our system are similar to previous work, new features, such as texture, RGB color, portrait (through face detection), and black-and-white, are included for individual preferences. Our goal of automatically ranking photographs is not intended for award-wining professional photographs but for photographs taken by amateurs, especially when individual preference is taken into account.

With the current widespread use of digital cameras, the process of selecting and maintaining personal photos is becoming an onerous task. To our knowledge, there has been little research on photo evaluation based on computational esthetics. Photographers around the world have established some general rules for taking good photos. Building upon artistic theories and human visual perception is difficult since the results tend to be subjective. Although automatically ranking award-wining professional photos may not be a sensible pursuit, such an approach may be reasonable for photos taken by amateurs. In the next section, we introduce rules for such a system.

Abstract Gaseous fluids may move slowly, as smoke does, or at high speed, such as occurs with explosions. High‐speed gas flow is always accompanied by low‐speed gas flow, which produces rich visual details in the fluid motion. Realistic visualization involves a complex dynamic flow field with both low and high speed fluid behavior. In computer graphics, algorithms to simulate gaseous fluids address either the low speed case or the high speed case, but no algorithm handles both efficiently. With the aim of providing visually pleasing results, we present a hybrid algorithm that efficiently captures the essential physics of both low‐ and high‐speed gaseous fluids. We model the low speed gaseous fluids by a grid approach and use a particle approach for the high speed gaseous fluids. In addition, we propose a physically sound method to connect the particle model to the grid model. By exploiting complementary strengths and avoiding weaknesses of the grid and particle approaches, we produce some animation examples and analyze their computational performance to demonstrate the effectiveness of the new hybrid method.

A brief biography of Jane Wilhelms is given highlighting her professional achievements.

The construction of a C/sup 1/ piecewise bicubic Bezier surface that interpolates a set of data points and lies on the same side of a given plane as the data points is presented. The main tasks in this construction process are the adjustment of the tangent vectors and the determination of the twist vectors at the data points. The tangent vectors are modified by decreasing their magnitudes. The twist vectors are first set by an energy minimization process and then filtered through a modification process to ensure the constructed surface lies on one side of the given plane. The technique for determining the twist vectors has an interpolation precision of cubic polynomials.

The paper describes a new spline formulation that supports deformation of polygonal shapes into smooth spline surface models. Once a polygonal shape with underlying rectangular topology is specified by the user, it is deformed into a smooth surface that interpolates all the polygonal vertices. The user can then modify the default smooth surface by increasing or decreasing the amount of deformation, either globally or locally. This is accomplished by interactively controlling the shape parameters associated with the polygonal vertices. This modeling paradigm is conceptually simple, and allows C/sup 2/ continuous surfaces to be easily designed, even by a novice user.

The paper develops four alternatives for modeling surfaces of the cornea and contact lenses. The cornea and contact lenses are generally smooth surfaces with possible discontinuities in circumferential or radial patterns. We define surfaces derived from semi-regular tensor product B-spline surfaces over a polar coordinate domain. The semi-regular partition allows finer control over the patch size, which is desirable for adaptive refinement. In geometric space, several patches meet at the origin, potentially resulting in a discontinuity. This is addressed by either imposing a system of constraints or blending the center region into a continuous function. The representations are fit to sampled data from a range of shapes and compared in terms of overall fit and fidelity at the origin. In the cases where constraint equations are used, their effectiveness and consequences on the resulting accuracy are assessed.

The parametric, geometric, or Frenet frame continuity of a rational curve has often been ensured by requiring the homogeneous polynomial curve associated with the rational curve to possess either parametric, geometric, or Frenet frame continuity, respectively. In this paper, we show that this approach is overly restrictive and derive the constraints on the associated homogeneous curve that are both necessary and sufficient to ensure that the rational curve is either parametrically, geometrically, or Frenet frame continuous.

Catmull-Rom splines have local control, can be either approximating or interpolating, and are efficiently computable. Experience with Beta-splines has shown that it is useful to endow a spline with shape parameters , used to modify the shape of the curve or surface independently of the defining control vertices. Thus it is desirable to construct a subclass of the Catmull-Rom splines that has shape parameters. We present such a class, some members of which are interpolating and others approximating. As was done for the Beta-spline, shape parameters are introduced by requiring geometric rather than parametric continuity. Splines in this class are defined by a set of control vertices and a set of shape parameter values. The shape parameters may be applied globally, affecting the entire curve, or they may be modified locally, affecting only a portion of the curve near the corresponding joint. We show that this class results from combining geometrically continuous (Beta-spline) blending functions with a new set of geometrically continuous interpolating functions related to the classical Lagrange curves . We demonstrate the practicality of several members of the class by developing efficient computational algorithms. These algorithms are based on geometric constructions that take as input a control polygon and a set of shape parameter values and produce as output a sequence of Bézier control polygons that exactly describes the original curve. A specific example of shape design using a low-degree member of the class is given.

The graphical simulation of a certain subset of hydrodynamics phenomena is examined. New algorithms for both modeling and rendering these complex phenomena are presented. The modeling algorithms deal with wave refraction in an ocean. Waves refract in much the same way as light. In both cases, the equation that controls the change in direction is Snell's law. Ocean waves are continuous but can be discretely decomposed into wave rays or wave orthogonals . These wave orthogonals are wave-traced in a manner similar to the rendering algorithm of ray-tracing. The refracted wave orthogonals are later traversed and their height contributions to the final surface are calculated using a sinusoidal shape approximation and the principle of wave superposition. The surface is then represented by Beta-splines , using the tension (or β2) shape parameter to easily add more complexity to the surface. The rendering algorithms are based on the use of texture maps and Fresnel's law of reflection. In each algorithm, two texture maps are used to simulate reflection and refraction . Based on surface normal orientation and Fresnel's law, a weighting is calculated that determines what fractions of reflected color and refracted color are assigned to a point. These algorithms are more efficient, though less accurate, alternatives to standard ray-tracing techniques.

A method is developed for surface-fitting from sampled data. Surface-fitting is the process of constructing a compact representation to model the surface of an object based on a fairly large number of given data points. In our case, the data is obtained from a real object using an automatic three-dimensional digitizing system. The method is based on an adaptive subdivision approach, a technique previously used for the design and display of free-form curved surface objects. Our approach begins with a rough approximating surface and progressively refines it in successive steps in regions where the data is poorly approximated. The method has been implemented using a parametric piecewise bicubic Bernstein-Bézier surface possessing G1 geometric continuity. An advantage of this approach is that the refinement is essentially local reducing the computational requirements which permits the processing of large databases. Furthermore, the method is simple in concept, yet realizes efficient data compression. Some experimental results are given which show that the representation constructed by this method is faithful to the original database.

Soft filling algorithms change the color of an anti-aliased region, maintaining the anti-aliasing of the region. The two published algorithms for soft filling work only if the foreground region is anti-aliased against a black background. This paper presents three new algorithms. The first fills against a region consisting of any two distinct colors, and is faster than the published algorithms on a pixel-by-pixel basis for an RGB frame buffer; the second fills against a region composed of three distinct colors; and the third fills against a region composed of four distinct colors. As the power of the algorithms increases, so do the number of assumptions they make, and the computational cost.

A new concept and method for line clipping is developed that describes clipping in an exact and mathematical form. The basic ideas form the foundation for a family of algorithms for two-dimensional, three-dimensional, and four-dimensional (homogeneous coordinates) line clipping. The line segment to be clipped is mapped into a parametric representation. From this, a set of conditions is derived that describes the interior of the clipping region. Observing that these conditions are all of similar form, they are rewritten such that the solution to the clipping problem is reduced to a simple max/min expression. For each dimension, the mathematics are discussed, an example is given, the algorithm is designed, and a performance test is conducted. The new algorithm is compared with the traditional Sutherland-Cohen clipping algorithm. Using randomly generated data, the new algorithm showed a 36 percent, 40 percent, and 79 percent improvement for two-dimensional, three-dimensional, and four- dimensional clipping, respectively. One of the advantages of this algorithm is the quick rejection of line segments that are invisible. In addition, this algorithm can be easily generalized for clipping against any convex viewing volume

The Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vectors at joints (geometric continuity) while providing bias and tension parameters, independent of the position of control vertices, by which the shape of a curve or surface can be manipulated. Using a restricted form of quintic Hermite interpolation, it is possible to allow distinct bias and tension parameters at each joint without destroying geometric continuity. This provides a new means of obtaining local control of bias and tension in piecewise polynomial curves and surfaces.

TensionThe Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vectors at joints (geometric continuity) while providing bias and tension parameters, independent of the position of control vertices, by which the shape of a curve or surface can be manipulated.Using a restricted form of quintic Hermite interpolation, it is possible to allow distinct bias and tension parameters at each joint without destroying geometric continuity.This provides a new means of obtaining local control of bias and tension in piecewise polynomial curves and surfaces.

Various techniques of curve representation have been developed and each has properties that make it more appropriate in certain situations than in others. Thus, it is very beneficial to be able to transform between formulations in order to invoke the one which is best suited to any particular instance. This concept has been applied to a set of four parametric spline curve formulations and is demonstrated in the TRANSPLINE interactive curve representation system. The available formulations are the interpolatory spline, uniform B-spline, spline under tension, and ν-spline. The mathematical theory of each formulation is briefly reviewed, the transformations between them are derived, and the system implementation is described.