In this paper, we propose a complete model handling physical simulation of deformable 1D objects. We formulate continuous expressions for stretching, bending and twisting energies. These expressions are mechanically rigorous and geometrically exact. Both elastic and plastic deformations are handled to simulate a wide range of materials. We validate the proposed model on several classical test configurations. The use of geometrical exact energies with dynamic splines provides very accurate results as well as interactive simulation time, which shows the suitability of the proposed model for constrained CAD applications. We illustrate the application potential of the proposed model by describing a virtual system for cable positioning, that can be used to test compatibility between planned fixing clip positions, and mechanical cable properties.
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. The performance of our system in terms of precision-recall diagram and binary classification accuracy (93%) is close to the best results to date for both overall system and individual features. Two personalized ranking user interfaces are provided: one is feature-based and the other is example-based. Although both interfaces are effective in providing personalized preferences, our user study showed that example-based was preferred by twice as many people as feature-based.
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 G
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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.
f r o n t l a y e r r e a r l a y e r wa t c h f a c e c o r r e c t e d f o r p r e s b y o p i a c o n v e n t i o n a l d i s p l a y s i n g l e -l a y e r p r e -f i l t e r i n g t wo -l a y e r p r e -f i l t e r i n g p e r c e i v e d i ma g e s d i s p l a y e d i ma g e sFigure 1: Correcting presbyopia using multilayer displays. A presbyopic individual observes a watch at a distance of 45 cm. The watch appears out of focus due to the limited range of accommodation. To read the watch, corrective eyewear (e.g., bifocals) must be worn with a +2.50 diopter spherical lens. (Left) As a substitute for eyewear, the watch can be modified to use a multilayer display containing two semi-transparent, light-emitting panels. The images displayed on these layers are pre-filtered such that the watch face appears in focus when viewed by the defocused eye. (Right) From left to right along the bottom row: the perceived image using a conventional display (e.g., an unmodified LCD), using prior single-layer pre-filtering methods, and using the proposed multilayer pre-filtering method. Corresponding images of the watch face are shown along the top row. Two-layer pre-filtering, while increasing the watch thickness by 6 mm, enhances contrast and eliminates ringing artifacts, as compared to prior single-layer pre-filtering methods. (Watch image c Timex Group USA, Inc.)
AbstractOptical 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.
Traditional computer graphics methods render images that appear sharp at all depths. Adding blur can add realism to a scene, provide a sense of scale, and draw a viewerÕs attention to a particular region of a scene. Our image-based blur algorithm needs to distinguish whether a portion of an image is either from a single object or is part of more than one object. This motivates two approaches to identify objects after an image has been rendered. We illustrate how these techniques can be used in conjunction with our image space method to add blur to a scene.
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