1,721,043 research outputs found
Geometric Representation and Grouping of Image Curves
No full textPerceptual organisation, while acknowledged to be important to computer vision, is often based on heuristics rather than geometrical methods. This thesis highlights the role which geometry plays in perceptual organisation including the geometric representation of image curves and the grouping of geometrically-related curves. First, the representation of image curves via B-splines is considered. Current methods are deficient because they do not fully take into account the main issues of spline fitting which include selecting the number and distribution of control points, and the parameterisation and sampling of the data points. By addressing these issues with a combination of active contours, the minimum description length principle and a structural-mechanics-inspired control point insertion strategy, superior results are obtained. Having provided a geometric representation for image curves, the grouping of curves related by affine symmetry transformations is investigated. Means for qua..
Stereo Coupled Active Contours
No full textWe consider how tracking in stereo may be enhanced by coupling pairs of active contours in different views via affine epipolar geometry and various subsets of planar affine transformations, as well as by implementing temporal constraints imposed by curve rigidity. 3D curve tracking is achieved using a submanifold model, where it is shown how the coupling mechanisms can be decomposed to cater for fixed and variable epipolar geometries. In the case of tracking planar curves, the canonical frame model is developed such that the various geometrical constraints needed in different situations may be efficiently selected. The results show that coupled active contours add consistency and robustness to tracking in stereo
Abstract Dynamic Shadow Elimination for Multi-Projector Displays
No full textA major problem with interactive displays based on frontprojection is that users cast undesirable shadows on the display surface. This situation is only partially-addressed by mounting a single projector at an extreme angle and prewarping the projected image to undo keystoning distortions. This paper demonstrates that shadows can be muted by redundantly-illuminating the display surface using multiple projectors, all mounted at different locations. However, this technique does not eliminate shadows: multiple projectors create multiple dark regions on the surface (penumbral occlusions). We solve the problem by using cameras to automatically identify occlusions as they occur and dynamically adjust each projector’s output so that additional light is projected onto each partially-occluded patch. The system is self-calibrating: relevant homographies relating projectors, cameras and the display surface are recovered by observing the distortions induced in projected calibration patterns. The resulting redundantly-projected display retains the high image quality of a single-projector system while dynamically correcting for all penumbral occlusions. Our initial two-projector implementation operates at 3 Hz. 1
A Theory for Photometric Self-Calibration of Multiple Overlapping Projectors and Cameras
No full text
Stereo Coupled Active Contours
No full textWe consider how tracking in stereo may be enhanced by coupling pairs of active contours in different views via affine epipolar geometry and various subsets of planar affine transformations, as well as by implementing temporal constraints imposed by curve rigidity. 3D curve tracking is achieved using a submanifold model, where it is shown how the coupling mechanisms can be decomposed to cater for fixed and variable epipolar geometries. In the case of tracking planar curves, the canonical frame model is developed such that the various geometrical constraints needed in different situations may be efficiently selected. The results show that coupled active contours add consistency and robustness to tracking in stereo. 1. Introduction The geometry underlying multiple camera views has been well studied, especially since it is the primary tool used in stereo vision and structure from motion techniques. Multi-view geometry has also been used in the monocular tracking of objects. The affine ac..
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