When using NURBS or subdivision surfaces as a design tool in engineering applications, designers face certain challenges. One of these is the presence of artifacts. An artifact is a feature of the ...surface that cannot be avoided by movement of control points by the designer. This implies that the surface contains spatial frequencies greater than one cycle per two control points. These are seen as ripples in the surface and are found in NURBS and subdivision surfaces and potentially in all surfaces specified in terms of polyhedrons of control points.
Ideally, this difference between designer intent and what emerges as a surface should be eliminated. The first step to achieving this is by understanding and quantifying the artifact observed in the surface.
We present methods for analysing the magnitude of artifacts in a surface defined by a quadrilateral control mesh. We use the subdivision process as a tool for analysis. Our results provide a measure of surface artifacts with respect to initial control point sampling for all B-Splines, quadrilateral box-spline surfaces and regular regions of subdivision surfaces. We use four subdivision schemes as working examples: the three box-spline subdivision schemes, Catmull–Clark (cubic B-spline), 4-3, 4-8; and Kobbeltʼs interpolating scheme.
Fertilizing intact plants with particular forms of nitrogen (N), at equal concentrations of total N, gives rise to N-form-specific morphological and physiological phenotypes. Urea amine nitrogen is ...only transiently available in soil, thus its effects on plants have not been as well-defined. By stabilizing the N source urea amine, we have begun to characterize a third phenotype in addition to those recognized for nitrate and ammonium. We show that non-limiting rates of stabilized amine nitrogen (SAN) induce specific traits in greenhouse-grown lettuce, that lead to increased yields compared to controls treated with conventional industry standard fertilizers, un-stabilized urea, calcium nitrate or ammonium nitrate. These were supplied at the same total weight of N, via the soil or foliarly, to seedlings of Lactuca sativa L. cv 'Tom Thumb' and/or 'Lollo Rosso'. Initially tap root length, lateral root development and leaf chlorophyll content are increased by SAN. As plants mature, leaf biomass increases at a faster rate under SAN nutrition, and larger harvest weights are finally attained, and/or a given head weight is achieved more rapidly. We conclude that plants respond positively to the maintenance of nitrogen in ureic-amine form, by initially partitioning more biomass to roots whilst increasing photosynthesis. These changes allow provision of more soil-sourced and carbon-based resources to the leaves of maturing plants. Leafy vegetable yields can be increased using stabilized urea amine fertilizer. We identify proxy traits for yield in young seedlings, which could be utilized in breeding and phenotyping programs for a wide range of species.
We deal with subdivision schemes based on arbitrary degree B‐splines. We focus on extraordinary knots which exhibit various levels of complexity in terms of both valency and multiplicity of knot ...lines emanating from such knots. The purpose of truncated multiple knot lines is to model creases which fair out. Our construction supports any degree and any knot line multiplicity and provides a modelling framework familiar to users used to B‐splines and NURBS systems.
We deal with subdivision schemes based on arbitrary degree B‐splines. We focus on extraordinary knots which exhibit various levels of complexity in terms of both valency and multiplicity of knot lines emanating from such knots. The purpose of truncated multiple knot lines is to model creases which fair out. Our construction supports any degree and any knot line multiplicity and provides a modelling framework familiar to users used to B‐splines and NURBS systems.
Surface artifacts are features in a surface which cannot be avoided by movement of control points. They are present in B-splines, box splines and subdivision surfaces. We showed how the subdivision ...process can be used as a tool to analyse artifacts in surfaces defined by quadrilateral polyhedra (
Sabin et al., 2005; Augsdörfer et al., 2011).
In this paper we are utilising the subdivision process to develop a generic expression which can be employed to determine the magnitude of artifacts in surfaces defined by any regular triangular polyhedra. We demonstrate the method by analysing box-splines and regular regions of subdivision surfaces based on triangular meshes: Loop subdivision, Butterfly subdivision and a novel interpolating scheme with two smoothing stages. We compare our results for surfaces defined by triangular polyhedra to those for surfaces defined by quadrilateral polyhedra.
► Surface artifacts are present in B-splines, box splines and subdivision surfaces. ► We present a generic expression to determine the magnitude of artifacts in surfaces. ► We demonstrate the method on surfaces based on triangular meshes. ► The artifact is affected by sampling, number of smoothing stages and their direction. ► We compare the results to surfaces based on quadrilateral meshes.
Free-Form Deformation (FFD) is a versatile and efficient modeling technique which transforms an object by warping the surrounding space. The conventional user-interface is a lattice of movable ...control points but this tends to be cumbersome and counterintuitive. Directly Manipulated Free-Form Deformation (DMFFD) allows the user to drag object points directly and has proven useful in an interactive sculpting context. A serious shortcoming of both FFD and DMFFD is that some deformations cause self-intersection of the object. This is unrealistic and compromises the object's validity and suitability for later use. An in-built self-intersection test is thus required for FFD and its extensions to be truly robust In this paper, we present the following novel results set of theoretical conditions for preventing self-intersection by ensuring the injectivity (one-to-one mapping) of FFD, an exact. (necessary and sufficient) injectivity test which is accurate but computationally costly, an efficient but approximate injectivity test which is a sufficient condition only, and a new form of DMFFD which acts by composing many small injective deformations. The latter expands the range of possible deformations without sacrificing the speed of the approximate test.
A typical goal when enhancing the contrast of images is to increase the perceived contrast without altering the original feel of the image. Such contrast enhancement can be achieved by modelling ...Cornsweet profiles into the image. We demonstrate that previous methods aiming to model Cornsweet profiles for contrast enhancement, often employing the unsharp mask operator, are not robust to image content. To achieve robustness, we propose a fundamentally different vector-centric approach with Cornsweet surfaces. Cornsweet surfaces are parametrised 3D surfaces (2D in space, 1D in luminance enhancement) that are extruded or depressed in the luminance dimension to create countershading that respects image structure. In contrast to previous methods, our method is robust against the topology of the edges to be enhanced and the relative luminance across those edges. In user trials, our solution was significantly preferred over the most related contrast enhancement method.
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•A novel image parametrisation approach based on B-spline surfaces.•Selective countershading guided by image-content and artistic input allowing for strong contrast enhancements that better respect the edge structure.•Psychophysical experimentation evaluating the visual quality of our results.
Despite its clinical importance, little is known of the epidemiology and population structure of
Candida glabrata.
C. glabrata possesses a mating type system similar to that in
Saccharomyces ...cerevisiae, however mating, meiosis and recombination have not been demonstrated. We performed multilocus sequence typing on a collection of 165 isolates to test for evidence of genetic recombination. A total of 3345
bp from six loci (
FKS,
LEU2,
NMT1,
TRP1,
UGP1, and
URA3) were sequenced for each isolate. The polymorphisms at these loci defined 34 sequence types. Significant evidence for a clonal population was revealed by the index of association and the number of phylogenetically compatible pairs of loci. However, 14 examples of phylogenetic incompatibility were also found. Thus we conclude that although
C. glabrata has a predominantly clonal population structure, the multiple phylogenetic incompatibilities found strongly suggest that recombination occurred during the evolution of
C. glabrata, and may infrequently still occur.
Multiresolution methods in geometric modelling are concerned with the generation, representation, and manipulation of geometric objects at several levels of detail. Applications include fast ...visualization and rendering as well as coding, compression, and digital transmission of 3D geometric objects. This book marks the culmination of the four-year EU-funded research project, Multiresolution in Geometric Modelling (MINGLE). The book contains seven survey papers, providing a detailed overview of recent advances in the various fields within multiresolution modelling, and sixteen additional research papers. Each of the seven parts of the book starts with a survey paper, followed by the associated research papers in that area. All papers were originally presented at the MINGLE 2003 workshop held at Emmanuel College, Cambridge, UK, 9-11 September 2003.
We reviewed the emergence of 13 cases of multi-resistant
Acinetobacter infection in burns patients over a 12-month period. The outbreak was started in a non-burn patient in the intensive care unit ...(ICU) that spread to burns patients in ICU and then the Burns Unit. The importance of opportunistic infection, potential risk factors, treatment and clinical outcome of
Acinetobacter infection in burns patients from this cluster of cases is described.
This paper implicates the movement of burns patients and medical equipment between ICU and the Burns Unit in the spread of this infection. Future design of Burn Units should aim to incorporate features to allow the management of all burns cases in one location with all intensive care, burns and theatre facilities built in close proximity.
Linear interpolation is the standard image blending method used in image compositing. By averaging in the dynamic range, it reduces contrast and visibly degrades the quality of composite imagery. We ...demonstrate how to correct linear interpolation to resolve this longstanding problem. To provide visually meaningful, high level control over the compositing process, we introduce three novel image blending operators that are designed to preserve key visual characteristics of their inputs. Our contrast preserving method applies a linear color mapping to recover the contrast lost due to linear interpolation. Our salience preserving method retains the most informative regions of the input images by balancing their relative opacity with their relative saliency. Our color preserving method extends homomorphic image processing by establishing an isomorphism between the image colors and the real numbers, allowing any mathematical operation defined on real numbers to be applied to colors without losing its algebraic properties or mapping colors out of gamut. These approaches to image blending have artistic uses in image editing and video production as well as technical applications such as image morphing and mipmapping.
Categories and Subject Descriptors (according to ACM CCS): I.3.3 Computer Graphics: Picture/Image Generation
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