17348246
Lighting interpolation by shadow morphing using intrinsic lumigraphs
Densely-sampled image representations such as the light field or lumigraph have been effective in enabling photorealistic image synthesis. Unfortunately, lighting interpolation with such representations has not been shown to be possible without the use of accurate 3D geometry and surface reflectance properties. In this paper we propose an approach to image-based lighting interpolation that is based on estimates of geometry and shading from relatively few images. We decompose captured light fields at different lighting conditions into intrinsic images (reflectance and illumination images), and estimate view-dependent scene geometries using multi-view stereo. We call the resulting representation an intrinsic lumigraph. In the same way that the lumigraph uses geometry to permit more accurate view interpolation, the intrinsic lumigraph uses both geometry and intrinsic images to allow high-quality interpolation at different views and lighting conditions. Joint use of geometry and intrinsic images is effective in the computation of shadow masks for shadow prediction at new lighting conditions. We illustrate our approach with images of real scenes.
122813254
Shape Ambiguities in Structure From Motion
This paper examines the fundamental ambiguities and uncertainties inherent in recovering structure from motion. By examining the eigenvectors associated with null or small eigenvalues of the Hessian matrix, we can quantify the exact nature of these ambiguities and predict how they affect the accuracy of the reconstructed shape. Our results for orthographic cameras show that the bas-relief ambiguity is significant even with many images, unless a large amount of rotation is present. Similar results for perspective cameras suggest that three or more frames and a large amount of rotation are required for metrically accurate reconstruction.
47117010
Stylizing 2.5-D video
In recent years considerable interest has been given to non-photorealistic rendering of photographs, video, and 3D models for illustrative or artistic purposes. Conventional 2D inputs such as photographs and video are easy to create and capture, while 3D models allow for a wider variety of stylization techniques, such as cross-hatching. In this paper, we propose using video with depth information (2.5-D video) to combine the advantages of 2D and 3D input. 2.5-D video is becoming increasingly easy to capture, and with the additional depth information, stylization techniques that require shape information can be applied. However, because 2.5-D video contains only limited shape information and 3D correspondence over time is unknown, it is difficult to create temporally coherent stylized animations directly from raw 2.5-D video. In this paper, we present techniques for processing 2.5-D video to overcome these drawbacks, and demonstrate several styles that can be created using these techniques.
41028764
Large environment rendering using plenoptic primitives
One of the most difficult tasks in computer graphics is to enable virtual walkthroughs in very large and complicated environments that are photorealistic, seamless, and in real time. Current image-based rendering techniques, while capable of photorealism and interactive speeds, have failed in practice to extend to visualizations of such environments. We demonstrate an approach that defines a virtual walkthrough experience using plenoptic primitives (PPs). A PP can be any type of local visual experience: 360/spl deg/ static panorama, panoramic video (PV), lumigraph/light field representation, or concentric mosaics (CMs). By combining them judiciously, user experience can be authored with significantly reduced effort while maintaining high-quality user experience. We illustrate our technique on synthetic and real environments using PVs and CMs and show how the problem of achieving smooth transitions among PVs and CMs can be solved by using position-dependent local geometries.
44673585
Characterization of Errors in Compositing Panoramic Images
A panoramic image has a 360° horizontal field of view, and it can provide the viewer the impression of being immersed in the scene. A panorama is created by first taking a sequence of images while rotating the camera about a vertical axis. These images are then projected onto a cylindrical surface before being seamlessly composited. The cross-sectional circumference of the cylindrical panorama is called thecompositing length. This work characterizes the error in compositing panoramic images due to errors in some of the intrinsic parameters. The intrinsic camera parameters that are considered are the camera focal length and the radial distortion coefficient. We show that the error in the compositing length is more sensitive to the error in the camera focal length. Especially important is the discovery that the relative error in compositing length is always smaller than the relative error in the focal length. This means that the error in focal length can be corrected by iteratively using the composited length to compute a new and more correct focal length. Thiscompositing approach to camera calibrationhas the advantages of not requiring both feature detection and separate prior calibration.
2215768
Separating reflections in human iris images for illumination estimation
A method is presented for separating corneal reflections in an image of human irises to estimate illumination from the surrounding scene. Previous techniques for reflection separation have demonstrated success in only limited cases, such as for uniform colored lighting and simple object textures, so they are not applicable to irises which exhibit intricate textures and complicated reflections of the environment. To make this problem feasible, we present a method that capitalizes on physical characteristics of human irises to obtain an illumination estimate that encompasses the prominent light contributors in the scene. Results of this algorithm are presented for eyes of different colors, including light colored eyes for which reflection separation is necessary to determine a valid illumination estimate
46430044
A new triple-layer OTC channel router
We propose a new algorithm for a triple-layer over-the-cell (OTC) routing in an irregular cell area. While other OTC routers assume that the cell structure is restricted to a certain type such as uniform height, our OTC router accepts both standard cells and custom cells. Our OTC channel routing consists of five steps: (i) double-layer routing, (ii) track-to-metal3 transformation, (iii) segment-to-metal3 transformation, (iv) segment-to-metal1 transformation, and (v) triple-layer routing. We prove that the transformation steps can be executed in linear time. The effectiveness of our algorithm is demonstrated through physical circuit layouts with fully customized cells. Our algorithm is applied to route MCNC benchmark circuits and Deutsch's difficult problem resulting in a significant reduction in channel area.
205396452
Video dejittering by bake and shake
Video jittering occurs when the horizontal lines of video image frames are randomly displaced due to the corruption of synchronization signals or electromagnetic interference during video transmission. Inspired by the recent Bayesian/variational dejittering model of Shen (SIAM J. Appl. Math., vol. 64, pp. 1691-1708, 2004), in the current paper we propose a novel dejittering approach nicknamed 'bake-and-shake.' The bake step is to apply Perona-Malik type nonlinear diffusions to 'melt away' or heat up the jittered video frames, based upon which the shake step is able to optimally estimate the individual line jitters and renormalize the jittered images. Numerical implementation of the bake-and-shake algorithm as well as several computational results are presented.
9186181
New simulation methods for MOS VLSI timing and reliability
A novel approach to incorporating the channel length modulation in a direct-equation solving fast timing simulator is presented along with a mixed event-driven and waveform relaxation algorithm to handle MOS VLSI circuits with feedback. Simulation speedup of 3N over SPICE-like simulators has been observed, where N is the number of transistors. The simulator is able to simulate circuits as large as 235000 transistors in 10 min real time. Also presented is a novel approach to fast hot-carrier reliability simulation. These methods make it possible to achieve accurate and fast hot-carrier reliability simulation of MOS circuits each with as many as hundreds of thousands of MOS transistors in a workstation environment.<<ETX>>
24075467
Analytic transient solution of general MOS circuit primitives
The exact analytic transient solution is presented for a general MOS circuit primitive. In the circuit primitive, I-V characteristics of transistors are modeled by quadratic equations and node voltages by piecewise-linear waveforms. The proposed MOS circuit primitive, of which an inverter is a special case, is shown to be more suitable for switch level and fast timing simulations than the commonly used inverter. For circuit simulation of medium-size digital circuits containing a few hundred transistors, the application of this analytic solution has resulted in two to three orders of speed improvement over the conventional circuit simulator. The speed improvement factor is expected to grow with the circuit size. It is also shown that the exact transient solution of a macromodel which models the charge sharing can be obtained in the same way. >
18755002
Color image decomposition and restoration
Meyer has recently introduced an image decomposition model to split an image into two components: a geometrical component and a texture (oscillatory) component. Inspired by his work, numerical models have been developed to carry out the decomposition of gray scale images. In this paper, we propose a decomposition algorithm for color images. We introduce a generalization of Meyer’s G norm to RGB vectorial color images, and use Chromaticity and Brightness color model with total variation minimization. We illustrate our approach with numerical examples.