Multiresolution modelling is a good method to achieve both quality and performance in the rendering of complex scenes. Within this framework, the detection and preservation of outstanding features, such us silhouettes...
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ISBN:
(纸本)9789898111203
Multiresolution modelling is a good method to achieve both quality and performance in the rendering of complex scenes. Within this framework, the detection and preservation of outstanding features, such us silhouettes, become very important. The goal of this paper is to present a technique based on Distance Transforms that allows to classify the elements of the mesh according to their proximity to both the internal and the external contours and makes use of this information for weighting the approximation error which will be tolerated during the mesh simplification process. The approach used in this work precomputes silhouettes for a given set of cameras and performs an estimation for any other point of view. The results obtained are evaluated in two ways: visually and using an objective metric that measures the geometrical difference between two polygonal meshes.
We present a method for creating 2 1/2D models from line drawings of opaque solid objects. As input, we use a single drawing composed of strokes indicative of surface geometry, but not of texture, color or shading. We...
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We present a method for creating 2 1/2D models from line drawings of opaque solid objects. As input, we use a single drawing composed of strokes indicative of surface geometry, but not of texture, color or shading. We attempt to allow the artist to draw naturally, differing from many previous approaches. Our system allows both perspective and orthographic projection to be used and we make no a priori assumptions about the type of model to be produced (i.e. planar, curved, normalon). The frontal geometry of the input drawing is reconstructed by placing constraints at the contours and solving a 2D variational system for the smoothest piecewise smooth surface. An analysis of line labelling allows us to determine what constraints are possible and/or required for each input line. However, because line labelling produces a combinatorial explosion of valid output geometries, we allow the user to guide the constraint selection and optimization with a simple user interface that abstracts the technical details away from the user. The system produces candidate reconstructions using different constraint values, from which the user selects the one that most closely approximates the model represented by the drawing. These choices allow the system to determine the constraints and reconstruct the model. The system runs at interactive speeds. (c) 2007 Published by Elsevier Ltd.
Distance Transforms have proven to be useful for many image processing applications. Nevertheless, they have only recently started to be used in computer graphics environments. The goal of this paper is to propose a n...
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ISBN:
(纸本)9728865392
Distance Transforms have proven to be useful for many image processing applications. Nevertheless, they have only recently started to be used in computer graphics environments. The goal of this paper is to propose a new technique based on Distance Transforms for detecting mesh elements which are close to the objects' external contour (from a given point of view), and using this information for weighting the approximation error which will be tolerated during the mesh simplification process.
This paper addresses the designers' activity and in particular the way designers express an object shape in 2D sketches through character lines and how these lines form a basis for sketching shapes in 3D. The tool...
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This paper addresses the designers' activity and in particular the way designers express an object shape in 2D sketches through character lines and how these lines form a basis for sketching shapes in 3D. The tools currently available in commercial CAS/CAD systems to manipulate the digital models are still not sufficiently suited to support design. In this paper, the so-called fully free-form deformation features (delta-F-4) are introduced as a modelling method to take into account the curve-oriented stylists' way of working. Both the advantages of a free-form surface deformation method and a feature-based approach are merged to define these high-level modelling entities allowing for a direct manipulation of surfaces through a limited number of intuitive parameters. Such features incorporate several characteristics designed to handle the uncertainties and/or inconsistencies of the designer's input during a sketching activity. In addition, a delta-F-4 classification is proposed to enable a fast access to the desired shape according to its semantics and characteristics. (c) 2005 Published by Elsevier Ltd.
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