Showing papers on "Distance transform published in 2001"

IDMaps: a global internet host distance estimation service

Abstract: There is an increasing need to quickly and efficiently learn network distances, in terms of metrics such as latency or bandwidth, between Internet hosts. For example, Internet content providers often place data and server mirrors throughout the Internet to improve access latency for clients, and it is necessary to direct clients to the nearest mirrors based on some distance metric in order to realize the benefit of the mirrors. We suggest a scalable Internet-wide architecture, called IDMaps, which measures and disseminates distance information on the global Internet. Higher level services can collect such distance information to build a virtual distance map of the Internet and estimate the distance between any pair of IP addresses. We present our solutions to the measurement server placement and distance map construction problems in IDMaps. We show that IDMaps can indeed provide useful distance estimations to applications such as nearest mirror selection.

Fast and simple 2D geometric proximity queries using graphics hardware

Abstract: We present a new approach for computing generalized proximity information of arbitrary 2D objects using graphics hardware. Using multi-pass rendering techniques and accelerated distance computation, our algorithm performs proximity queries not only for detecting collisions, but also for computing intersections, separation distance, penetration depth, and contact points and normals. Our hybrid geometry and image-based approach balances computation between the CPU and graphics subsystems. Geometric object-space techniques coarsely localize potential intersection regions or closest features between two objects, and image-space techniques compute the low-level proximity information in these regions. Most of the proximity information is derived from a distance field computed using graphics hardware. We demonstrate the performance in collision response computation for rigid and deformable body dynamics simulations. Our approach provides proximity information at interactive rates for a variety of simulation strategies for both backtracking and penalty-based collision responses.

Text identification in complex background using SVM

Abstract: The paper presents a fast and robust algorithm to identify text in image or video frames with complex backgrounds and compression effects. The algorithm first extracts the candidate text line on the basis of edge analysis, baseline location and heuristic constraints. Support Vector Machine (SVM) is then used to identify text line from the candidates in edge-based distance map feature space. Experiments based on a large amount of images and video frames from different sources showed the advantages of this algorithm compared to conventional methods in both identification quality and computation time.

Distance-field based skeletons for virtual navigation

Abstract: We present a generic method for rapid flight planning, virtual navigation and effective camera control in a volumetric environment. Directly derived from an accurate distance from boundary (DFB) field, our automatic path planning algorithm rapidly generates centered flight paths, a skeleton, in the navigable region of the virtual environment. Based on precomputed flight paths and the DFB field, our dual-mode physically based camera control model supports a smooth, safe, and sticking-free virtual navigation with six degrees of freedom. By using these techniques, combined with accelerated volume rendering, we have successfully developed a real-time virtual colonoscopy system on low-cost PCs and confirmed the high speed, high accuracy and robustness of our techniques on more than 40 patient datasets.

Deformed distance fields for simulation of non-penetrating flexible bodies

Abstract: We present a novel penetration depth estimation algorithm based on the use of deformed distance fields for simulation of non-penetrating flexible bodies. We assume that the continuum of non-rigid models are discretized using standard techniques, such as finite element methods. As the objects deform, the distance fields are deformed accordingly to estimate penetration depth, allowing enforcement of non-penetration constraints between two colliding elastic bodies. Our approach can automatically handle self-penetration and inter-penetration in a uniform manner. We demonstrate its effectiveness on moderately complex animated scenes.

A complete distance field representation

Abstract: Distance fields are an important volume representation. A high quality distance field facilitates accurate surface characterization and gradient estimation. However, due to Nyquist's Law, no existing volumetric methods based on the linear sampling theory can fully capture surface details, such as corners and edges, in 3D space. We propose a novel complete distance field representation (CDFR) that does not rely on Nyquist's sampling theory. To accomplish this, we construct a volume where each voxel has a complete description of all portions of surface that affect the local distance field. For any desired distance, we are able to extract a surface contour in true Euclidean distance, at any level of accuracy, from the same CDFR representation. Such point-based iso-distance contours have faithful per-point gradients and can be interactively visualized using splatting, providing per-point shaded image quality. We also demonstrate applying CDFR to a cutting edge design for manufacturing application involving high-complexity parts at un-precedented accuracy using only commonly available computational resources.

Image creating device and image creating method

Abstract: An image-capturing unit generates an image signal corresponding to an image of a subject formed by a photographing optical system. A point spread function generating unit generates varying point spread functions corresponding to various distances based upon two-dimensional distance distribution information indicating the two-dimensional distance distribution of the subject detected by a distance detection unit and an image blur signal indicating an image blur occurring during the exposure period which is detected by a blur detection unit. An image repair unit divides the image signal into partial images based upon the distance distribution information, executes image processing to repair the blur in the individual partial images by using the point spread functions corresponding to the various distances and creates a whole image by synthesizing the partial images in which the blur has been repaired.

Facial Reconstruction Using Volumetric Data

Abstract: In this paper we demonstrate computer aided techniques in the area of the reconstruction of facial features from skeletal remains. We outline the desired features of a system for skull identification, and demonstrate our progress in the area which builds upon our previous work on distance fields for volumetric data. In addition to the application we demonstrate an accurate 3D closing operator in practise on large data sets, cross correlation for automatic feature detection, and the current output from the technique which uses a 2D warp of the 3D distance field.

A pseudo-distance map for the segmentation-free skeletonization of gray-scale images

Abstract: In this paper we introduce a new tool, called a pseudo-distance map (PDM), for extracting skeletons from grayscale images without region segmentation or edge detection. Given an edge-strength function (ESF) of a gray-scale image, the PDM is computed from the ESF using the partial differential equations we propose. The PDM can be thought of as a relaxed version of a Euclidean distance map. Therefore, its ridges correspond to the skeleton of the original gray-scale image and it provides information on the approximate width of skeletonized structures. Since the PDM is directly computed from the ESF without thresholding it, the skeletonization result is generally robust and less noisy. We tested our method using a variety of synthetic and real images. The experimental results show that our method works well on such images.

Vessel segmentation with nodule detection

Abstract: A region-growing method for identifying nodules in an anatomical volume segments a 3-D image volume by controlled voxel growth from seed points. The process is based on creation and use of a distance map for tracking the distance of vessel voxels from a predetermined location. A volume map is created that identifies the largest sphere that can pass between a voxel and a predetermined location without touching a non-vessel voxel. The ratio between the distance map and the volume map is analyzed to find regions more likely to contain nodules, the features of which can be extracted or otherwise highlighted.

Distance based constraints for adaptively sampled distance fields

Abstract: A method edits a graphics object with a computer implemented tool by first representing the graphics object by an adaptively sampled distance field, and defining a mask by a distance field. Then, the tool is iteratively moved with respect to the object while constraining the movement according to the mask to edit the object.

Shape representation using space filled sub-voxel distance fields

Abstract: Voxelisation is the process of converting a source object of any data type into a three-dimensional grid of voxel values. This voxel grid should represent the original object as closely as possible, although some inaccuracies will occur due to the discrete nature of the voxel grid representation. In this paper we report our ongoing research into methods for representing objects as voxelised distance fields, in particular we report fast methods for accurate distance field production. A review of current alternative voxelisation methods is also given.

Low-cost implementation of distance maps for path planning using matrix quadtrees and octrees

Abstract: Hierarchical tree representations are used for computing and representing distance maps in homogeneous or weighted 2D and 3D environments. It is shown that the matrix forms of quadtree and octree descriptions are proper for storing not only image or spatial data but also distance data. Distance maps are used in collision-free path planning in environments with static obstacles. The resulting sequences of free-region quadrants and octants enable to compute distance-optimized paths to the chosen resolution level. More illustrative examples are included and analyzed for 2D and 3D workspaces.

Fast multidimensional parallel Euclidean distance transform based on mathematical morphology

Abstract: The paper presents a novel Euclidean distance transform algorithm formulated under the mathematical morphology approach. The distance transform is an erosion by a structuring function dependent on the distance metric used. To achieve high speed performance, the squared Euclidean distance structuring function is decomposed into a family of four one-dimensional two-point structuring functions. The erosion algorithm is based on a propagation scheme which resulted in an overall Euclidean distance transform algorithm very simple to code and understand, yet with speed performance compared to the Chamfer 3-5-7 sequential raster and anti-raster algorithm.

Two-dimensional object alignment based on the robust oriented Hausdorff similarity measure

Abstract: This paper proposes an oriented Hausdorff similarity (OHS) measure for robust object alignment. The OHS measure is introduced by replacing the distance concept of conventional Hausdoff distance (HD) algorithms by the similarity concept of the Hough transform (HT). The proposed algorithm can be considered as the modified directed HT using the distance transform (DT). The orientation information at each pixel is also used to remove incorrect correspondences.

Fast skeletonization algorithm for 3D elongated objects

Abstract: A novel one-pass 3D thinning algorithm is proposed in this paper. 3D thinning can be regarded as an essential step in many image-processing tasks such as image quantification, image compression, motion tracking, path generation, and object navigation. The proposed algorithm generates both connected and non-connected skeletons. It is faster and more accurate than currently available techniques in the literature. In addition, it adaptively removes spurious branches of the skeleton, and hence, generates a smooth and refined skeleton, representing the essential structure of 3D elongated objects such as vessels, airways, and other similar organic shapes.

Two and three dimensional skeletonization

Abstract: A method is disclosed for determining skeletons of any two dimensional images and three-dimensional skeletons of vessel trees. In the three dimensional case, the method takes a binary volume of any vessel tree as input and produces centred, connected and one-voxel wide skeleton of the input vessel tree. In the two dimensional case, centred, connected and one-pixel wide skeletons of input binary images are produced. The method includes the steps of: (1) calculating a 3D/2D distance transform, (2) locating local maximum voxels/pixels, one-voxel/pixel wide valley voxels/pixels, and two-voxel/pixel wide valley voxels/pixels, (3) propagating skeletal elements to get a full set of skeletal elements, and (4) removing redundant local maximum voxels/pixels to obtain a one-voxel/pixel wide skeleton.

Estimation of local defocus distance and geometric distortion based on scanned image features

Abstract: A method of estimating local defocus distance from a conventionally scanned image is provided. More particularly, the method of estimating defocus distance in a scanned image of a non-planar original object, such as an open book, includes scanning at least a portion of the book in order to produce scanned image data. An image feature obtainable from the scanned image data and a quantitative metric corresponding to the image feature are selected. Image feature data is extracted from the scanned image data and compared to a predetermined calibration relationship between the selected image feature and defocus distance in order to calculate a plurality of defocus distances, which are organized into a defocus distance map. The defocus distance map may be used in the subsequent correction of geometric distortions, blurring defects, and illumination variations adjacent the binding of an open book.

Image processor for area around vehicle and recording medium

Abstract: PROBLEM TO BE SOLVED: To provide an image processor used for the area around a vehicle and capable of displaying a conspicuous image by converting a birds-eye view image to an image similar to that photographed with a camera or the like and a recording medium. SOLUTION: Step 140 moves a first birds-eye view image stored in an image memory B based on the degree of the movement of a vehicle to obtain the birds-eye view image obtained after moving the vehicle. Step 160 composites the birds-eye view image obtained after moving the vehicle and a second birds- eye view image to prepare a composite birds-eye view image. Step 180 applies reverse birds-eye view conversion to the composite birds-eye view image to prepare a projected image. Step 190 stores the projected image in an image memory C. Step 200 adds an image displaying the vehicle to display the projected image stored in the image memory C on a monitor 3. COPYRIGHT: (C)2003,JPO

System and method for sculpting digital models

Abstract: A system interactively edits a graphics object. The system includes a user interface for setting editing parameters, and providing a model of the graphics object. An adaptively sample distance field is generated from the model, and an interactive editor manipulates the adaptively sampled distance field. The manipulated adaptively sampled distance field is then converted to rendering primitives to be rendered by a rendering engine.

Adaptive image filtering based on a distance transform

Abstract: A method for reducing visual artifacts in reconstructed images. One embodiment of the method determines edge energy for each pixel in the image and then compares the edge energy for each pixel to a threshold, producing an edge map. A distance transform is then used to produce a filter map and a filter is applied to pixel in the image, such that the filter applied is dependent upon a filter map value for each pixel. An output value for each pixel is then produced.

System and method for modeling graphics objects

Abstract: A system models a graphics object by first providing a model of the object, generation parameters specifying a fixed level-of-detail, and conversion parameters specifying variable levels-of-detail. An adaptively sampled distance field having the fixed level-of-detail is generated from the model, and the adaptively sampled distance field is converted from the fixed level-of-detail to the variable levels-of-detail while concurrently generating rendering primitives.

System and method for generating adaptively sampled distance fields with bounded distance trees

Abstract: A method generates an adaptively sampled distance field of an object by first defining a candidate cell of the adaptively sampled distance field. Then, distance values for the candidate cell are determined and stored in a bounded distance tree. The candidate cell is recursively subdividing into subdivided cells of the adaptively sampled distance field while determining and storing corresponding distance values of the subdivided cells in the bounded distance tree until a termination condition is reached. Lastly, the distance values are appended to the corresponding cells to generate the adaptively sampled distance field of the object.

System and method for converting range data to 3D models

Abstract: A method converts range data of an object to a model of the object by first generating an adaptively sampled distance field from the range data. The adaptively sampled distance field is then edited to produce the model. The range data can include a plurality of range images that are converted to range meshes in a single coordinate system, and an adaptively sampled distance field is generated for each of the range meshes.

A rapid method for planning paths in three dimensions for a small aerial robot

Abstract: This paper describes a path planning method for a small autonomous aerial vehicle to be used for inspecting overhead electricity power lines. A computational algorithm is described which converts a standard three dimensional array representation of one or more obstacles in the vehicle's environment into an octree and a connectivity graph. This achieves a significant reduction in computer memory usage and an increase in execution speed when the graph is searched. Path planning is based on a three-dimensional extension of the distance transform. Test results demonstrate rapid and effective operation of the planner within different workspaces.

Two algorithms for computing the euclidean distance transform

Abstract: Given an n × n binary image of white and black pixels, we present two optimal algorithms for computing the distance transform and the nearest feature transform using the Euclidean metric. The first algorithm is a fast sequential algorithm that runs in linear time in the input size. The second is a parallel algorithm that runs in O(n2/p) time on a linear array of p processors, p, 1 ≤ p ≤ n.

Conversion of adaptively sampled distance fields to triangles

Abstract: A method for converts an adaptively sampled distance field of a graphics model to a triangle model, The adaptively sampled distance field includes surface cells storing distance values that have corresponding gradients. A vertex is assigned to a center location of each surface cell. The vertices of neighboring surface cells are connected to form triangles while satisfying a predetermined constraint. Then, each vertex is moved, in a single step, to a new location according to the distance value and corresponding gradient of the vertex to substantially conform the triangles to a surface of the model.

Erosion and Dilation on 2-D and 3-D Digital Images: A New Size-Independent Approach

Abstract: This paper presents a new approach to achieve ele-mentary neighborhood operations on both 2D and3D binary images by using the Extreme VerticesModel (EVM),a recent orthogonal polyhedra repre-sentation applied to digital images. The operationsdeveloped here are erosion and dilation. In contrastwith previous techniques, this method do not use avoxel-based approach but deal with the inner sec-tions of the object. It allows to build an image size-independent algorithm. The proposed method alsoadmits the use of structuring elements of arbitrarysize and allows to treat 2D and 3D images in iden-tical way using the same algorithm. 1 Introduction A 3D digital image (or volume dataset) can be rep-resented as a map , in such away that every point is assigned a value represent-ing its color. In a binary image the image set is  . In [10] a 3D digital image is defined as anunion of voxels i.e. upright unit cubes whose ver-tices have integer coordinates. Analogously, a 2Ddigital image is defined as a union of pixels. In or-der to generalize this term, we will call the elementsin a n-dimensional digital image n-voxels.The most extensive class of binary images pro-cessing operations is sometimes collectively de-scribed as morphological operations [5]. This in-cludes erosion and dilation which are the base ofmost morphological operations such as opening,closing or hit-or-miss transform. The operations areused in several tasks such as elimination of smallspurious objects, smoothing of object boundaries,