14,774 research outputs found
Fast Reliable Ray-tracing of Procedurally Defined Implicit Surfaces Using Revised Affine Arithmetic
No full textFast and reliable rendering of implicit surfaces is an important area in the field of implicit modelling. Direct rendering, namely ray-tracing, is shown to be a suitable technique for obtaining good-quality visualisations of implicit surfaces. We present a technique for reliable ray-tracing of arbitrary procedurally defined implicit surfaces by using a modification of Affine Arithmetic called Revised Affine Arithmetic. A wide range of procedurally defined implicit objects can be rendered using this technique including polynomial surfaces, constructive solids, pseudo-random objects, procedurally defined microstructures, and others. We compare our technique with other reliable techniques based on Interval and Affine Arithmetic to show that our technique provides the fastest, while still reliable, ray-surface intersections and ray-tracing. We also suggest possible modifications for the GPU implementation of this technique for real-time rendering of relatively simple implicit models and for near real-time for complex implicit models
An Exact Representation of Polygonal Objects by C1-continuous Scalar Fields Based on Binary Space Partitioning
No full textThe problem considered in this work is to find a dimension independent algorithm for the generation of signed scalar fields exactly representing polygonal objects and satisfying the following requirements: the defining real function takes zero value exactly at the polygonal object boundary; no extra zero-value isosurfaces should be generated; C1 continuity of the function in the entire domain. The proposed algorithms are based on the binary space partitioning (BSP) of the object by the planes passing through the polygonal faces and are independent of the object genus, the number of disjoint components, and holes in the initial polygonal mesh. Several extensions to the basic algorithm are proposed to satisfy the selected optimization criteria. The generated BSP-fields allow for applying techniques of function-based modelling to already existing legacy objects from CAD and computer animation areas, which is illustrated by several examples
Interactive ray shading of FRep objects
No full textIn this paper we present a method for interactive rendering general procedurally defined functionally represented (FRep) objects using the acceleration with graphics hardware, namely Graphics Processing Units (GPU). We obtain interactive rates by using GPU acceleration for all computations in rendering algorithm, such as ray-surface intersection, function evaluation and normal computations. We compute primary rays as well as secondary rays for shadows, reflection and refraction for obtaining high quality of the output visualization and further extension to ray-tracing of FRep objects. The algorithm is well-suited for modern GPUs and provides acceptable interactive rates with good quality of the results. A wide range of objects can be rendered including traditional skeletal implicit surfaces, constructive solids, and purely procedural objects such as 3D fractals
Douglas Alexander Stewart, poet, author and playwright
No full textDouglas Alexander Stewart, poet, author and playwrigh
Feature based volumes for implicit intersections.
No full textThe automatic generation of volumes bounding the intersection of two implicit surfaces (isosurfaces of real functions of 3D point coordinates) or feature based volumes (FBV) is presented. Such FBVs are defined by constructive operations, function normalization and offsetting. By applying various offset operations to the intersection of two surfaces, we can obtain variations in the shape of an FBV. The resulting volume can be used as a boundary for blending operations applied to two corresponding volumes, and also for visualization of feature curves and modeling of surface based structures including microstructures
Author inscription in William Hazlitt, essayist and critic; selections from his writings, with a memoir, biographical and critical by Alexander Ireland
No full textAuthor's gift inscription, "To W. C. Hazlitt Esq with kind regards, from Alexr Ireland," with tipped-in review of the book.ASU Library edition has inscription from Ireland to Hazlitt [a child of William Hazlitt?].
Hazlitt , William, 1778-1830.
Ireland, Alexander, 1810-1894
BSP-fields: An Exact Representation of Polygonal Objects by Differentiable Scalar Fields Based on Binary Space Partitioning
No full textThe problem considered in this work is to find a dimension independent algorithm for the generation of signed scalar fields exactly representing polygonal objects and satisfying the following requirements: the defining real function takes zero value exactly at the polygonal object boundary; no extra zero-value isosurfaces should be generated; C1 continuity of the function in the entire domain. The proposed algorithms are based on the binary space partitioning (BSP) of the object by the planes passing through the polygonal faces and are independent of the object genus, the number of disjoint components, and holes in the initial polygonal mesh. Several extensions to the basic algorithm are proposed to satisfy the selected optimization criteria. The generated BSP-fields allow for applying techniques of the function-based modeling to already existing legacy objects from CAD and computer animation areas, which is illustrated by several examples
The Author of the Alexander Romance
No full textThis paper, which is based on a portion of the introduction of the author’s edition of Il Romanzo di Alessandro (Mondadori: Fondazione Valla 2007), surveys the generic components of the Alexander Romance in an attempt to arrive at a definition of the work. The argument builds on Merkelbach’s categorisation of elements and uses Fusillo’s insight into the novel as an ‘encyclopaedic genre’ to propose that ‘historical novel’ is not, as Hägg contended, a misnomer for the work. The main components I discuss are: ‘life’; praxeis; chreiai; Cynic elements, including choliambic poetry and utopian perspectives; and the Egyptian aspects of the narrative. A concluding jeu d’esprit offers a characterisation of the putative author, his antecedents and his process of composition.Richard Stoneman was for 25 years editor for classics at Croom Helm and then Routledge. In 1997 he was appointed an Honorary Fellow in the department of classics, University of Exeter. After retiring from publishing in 2006 he has been pursuing his researches on the Alexander legends and teaching a course on the subject at Exeter. His Penguin translation of the Alexander Romance was published in 1991, and a volume of translated Legends of Alexander the Great appeared from Everyman in 1994. Also in 1994 he co-edited Greek Fiction with John Morgan. His edition of the Greek recensions of the Alexander Romance was published (volume I) by the Fondazione Valla in 2007 – volumes II and III will follow over the next few years – and his Alexander the Great: A Life in Legend appeared from Yale University Press in spring 2008. He is the author of a number of other books on Greek history and travel, and is writing a book on oracles
Multi-scale space-variant FRep cellular structures
No full textExisting mesh and voxel based modeling methods encounter difficulties when dealing with objects containing cellular structures
on several scale levels and varying their parameters in space. We describe an alternative approach based on using real functions evaluated procedurally at any given point. This allows for modeling fully parameterized, nested and multi-scale cellular
structures with dynamic variations in geometric and cellular properties. The geometry of a base unit cell is defined using Function Representation (FRep) based primitives and operations. The unit cell is then replicated in space using periodic
space mappings such as sawtooth and triangle waves. While being replicated, the unit cell can vary its geometry and topology due
to the use of dynamic parameterization. We illustrate this approach by several examples of microstructure generation within a given volume or
along a given surface. We also outline some methods for direct rendering and fabrication not involving auxiliary mesh and voxel
representations
Author Correction: The dengue-specific immune response and antibody identification with machine learning
No full textCorrection to: npj Vaccineshttps://doi.org/10.1038/s41541-023-00788-7, published online 20 January 2024 In this article, the affiliation details for author Alexander Horst were incorrectly given as Alexander Horst1,2 but should have been Alexander Horst1 and other affiliations are renumbered. The original article has been corrected
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