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In this paper we propose a local-shape based method for correcting shape-from- shading information for surface height recovery of faces. The underpinning idea comes from the observation that subtle changes in the elements of a gradient field can cause notable changes in its integrated surface. One of the problems with reliable face surface reconstruction using shape-from-shading is that local errors...
When unpolarised light is reflected from a smooth dielectric surface, it is spontaneously partially polarised. This process applies to both specular and diffuse reflection, although the effect is greatest for specular reflection. This paper is concerned with exploiting this phenomenon by processing images of smooth dielectric objects to recover surface normals and hence height. The paper presents...
We propose a new approach for the reconstruction of 3D CAD models from paper drawings. Our method uses a combination of the well-known fleshing-out-projections method and accumulation techniques from image processing to reconstruct part models. It should provide a comfortable method to handle inaccuracies and missing elements unavoidable in scanned paper drawings while giving the user the chance to...
We present a new method of segmenting planar regions when an uncalibrated camera undergoes (near) pure translation. We show that, for pure translation parallel to a plane, the relation between the two views, when expressed in a reciprocal-polar $(\frac{1}{r}, \theta)$ space, is a pure shift in the $(\frac{1}{r})$ dimension for a given value of θ. Furthermore, we show that the magnitude of...
In this paper an algorithm that performs the tracking of points in a calibrated and noisy image sequence is presented. The candidate points to be tracked must satisfy certain constraints that can be deduced from the multiple view geometry. The idea is to consider as noisy points those candidates which cannot be tracked in the sequence. The robustness of the algorithm has been verified on simulated...
This paper deals with the problem of low level representation of 3D image contents. The presented solution makes use of multiresolution techniques to recover the so-called visual patterns or integral features that form images. It consists of decomposing the image into a set of elementary image features, representing frequency channels, using a filter bank, and grouping them by means of clustering...
We present a 3D representation that is based on the processing in the visual cortex by simple, complex and end-stopped cells. We improved multiscale methods for line/edge and keypoint detection, including a method for obtaining vertex structure (i.e. T, L, K etc). We also describe a new disparity model. The latter allows to attribute depth to detected lines, edges and keypoints, i.e., the integration...
Assuming a model composed of both parallel directional lighting and ambient illumination, this paper presents a method using a spherical calibration object to estimate the orientation of directional lighting together with the strengths of both types of light source. A set of experimental results showing the performance of the method proposed is included and discussed at the end of the paper.
We address the validation of the current sensed environmental state against a model known from earlier perception. Our surface based approach compares 3D range data of a built environment against an a priori scene model with the analysis of identified differences facilitating the hypothesis of causal structural changes within the scene. Experimental results show good success rates in identifying...
We present a simple calibration method for computing the extrinsic parameters (pose) and intrinsic parameters (focal length and principal point) of a camera by imaging a pattern of known geometry. Usually, the patterns used in calibration algorithms are complex to build (three orthogonal planes) or need a lot of features (checkerboard-like pattern). We propose using just two concentric circles that,...
This paper presents a simple but efficient matching methodology for three-dimensional object recognition using a modified exoskeleton (mES) and Hausdorff distance transform. The aim of this paper is to propose a method that can be used in computer vision system for robots or in digital image retrieval. The most significant part of this method is that it is less susceptible to distortion caused by...
We present a new approach to recognize 3D objects in an image taking the available information in it. To reach this aim a method based on a two step algorithm will be developed. In the first step, each 3D model will be converted in a set of 2D images using an aspect graph algorithm in which the concept of visual event is defined as the moment when the projective invariants got from the model have...
Most matching methods assume that all pixels of a correlation window have equal depths and find correspondences by comparing this local window of pixels. However, this assumption is not valid at depth discontinuities and wide baseline images. In this paper, a new method to construct the local planar patches called corner-edge-regions (CERs) is introduced. Based on this adaptive plane identification...
This paper contains a study on image matching techniques based on image gradients. Gradients of the intensity signal play the very important role in the human visual system and also in computer vision. Since the onset of computer image processing, features, in a form of gradients, have been used for matching. However, the second part of a matching process is a choice of the matching criterion, called...
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