scholarly journals Computing layered surface representations: an algorithm for detecting and separating transparent overlays

2003 ◽  
Author(s):  
M. Singh ◽  
Xiaolei Huang
Keyword(s):  
Surface Representations

Three-Dimensional Reconstruction of Native Androctonus Australis Hemocyanin

1990 ◽  
Vol 48 (1) ◽  
pp. 452-453
Author(s):  
Nicolas Boisset ◽  
Jean-Christophe Taveau ◽  
Jean Lamy ◽  
Terence Wagenknecht ◽  
Michael Radermacher ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Body ◽  
Body Surface ◽  
Three Dimensional ◽  
Staining Technique ◽  
Three Dimensional Reconstruction ◽  
Dimensional Reconstruction ◽  
View Reconstruction ◽  
Surface Representations ◽  
Top View

Hemocyanin, the respiratory pigment of the scorpion Androctonus australis is composed of 24 kidney shaped subunits. A model of architecture supported by many indirect arguments has been deduced from electron microscopy (EM) and immuno-EM. To ascertain, the disposition of the subunits within the oligomer, the 24mer was submitted to three-dimensional reconstruction by the method of single-exposure random-conical tilt series.A sample of native hemocyanin, prepared with the double layer negative staining technique, was observed by transmisson electron microscopy under low-dose conditions. Six 3D-reconstructions were carried out indenpendently from top, side and 45°views. The results are composed of solid-body surface representations, and slices extracted from the reconstruction volume.The main two characters of the molecule previously reported by Van Heel and Frank, were constantly found in the solid-body surface representations. These features are the presence of two different faces called flip and flop and a rocking of the molecule around an axis passing through diagonnally opposed hexamers. Furthermore, in the solid-body surface of the top view reconstruction, the positions and orientations of the bridges connecting the half molecules were found in excellent agreement with those predicted by the model.

Designing and Mapping Trimming Curves on Surfaces Using Orthogonal Projection

1990 ◽  
Author(s):  
Joseph Pegna ◽  
Franz-Erich Wolter
Keyword(s):  
Differential Equation ◽  
Orthogonal Projection ◽  
Broad Class ◽  
Design Tool ◽  
Space Curve ◽  
Computationally Efficient ◽  
Curves On Surfaces ◽  
Surface Representations ◽  
Differential Properties ◽  
Surface Curve

Abstract In the design and manufacturing of shell structures it is frequently necessary to construct trimming curves on surfaces. The novel method introduced in this paper was formulated to be coordinate independent and computationally efficient for a very general class of surfaces. Generality of the formulation is attained by solving a tensorial differential equation that is formulated in terms of local differential properties of the surface. In the method proposed here, a space curve is mapped onto the surface by tracing a surface curve whose points are connected to the space curve via surface normals. This surface curve is called to be an orthogonal projection of the space curve onto the surface. Tracing of the orthogonal projection is achieved by solving the aforementionned tensorial differential equation. For an implicitely represented surface, the differential equation is solved in three-space. For a parametric surface the tensorial differential equation is solved in the parametric space associated with the surface representation. This method has been tested on a broad class of examples including polynomials, splines, transcendental parametric and implicit surface representations. Orthogonal projection of a curve onto a surface was also developed in the context of surface blending. The orthogonal projection of a curve onto two surfaces to be blended provides not only a trimming curve design tool, but it was also used to construct smooth natural maps between trimming curves on different surfaces. This provides a coordinate and representation independent tool for constructing blend surfaces.

scholarly journals Multiple regression reveals 3D internal surface representations

2010 ◽  
Vol 2 (7) ◽  
pp. 310-310
Author(s):  
B. A. Bacon ◽  
F. Gosselin ◽  
P. Mamassian
Keyword(s):  
Multiple Regression ◽  
Internal Surface ◽  
Surface Representations

scholarly journals Extracting Surface Representations from Rim Curves

2006 ◽  
pp. 732-741 ◽  
Author(s):  
Hai Chen ◽  
Kwan-Yee K. Wong ◽  
Chen Liang ◽  
Yue Chen
Keyword(s):  
Surface Representations

scholarly journals Introduction: phonetics in phonology

Phonology ◽  
2001 ◽  
Vol 18 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Carlos Gussenhoven ◽  
René Kager
Keyword(s):  
Criminal Law ◽  
Criminal Code ◽  
The Internet ◽  
Social Perceptions ◽  
Lexical Representations ◽  
The People ◽  
Use Of The Internet ◽  
Surface Representations ◽  
Definition Of ◽  
The Way

If there is such a person as the average phonologist, he might have a conception of the relation between phonetics and phonology that comes close to the relation between social perceptions of crimes and a Code of Criminal Law. The Code's definition of various types of crimes and the penalty each type carries ultimately reflect, to put it crudely, the feelings of the people. Also, the Code's development will reflect social change. Criminal codes will typically incorporate the changing perceptions of the general public, and will now begin to include articles devoted to the use of the Internet, for instance. But at the end of the day, what counts in a law suit is what is in the Criminal Code, not the feelings of the people. So it is with phonology. It is easy to show that lexical forms are frequently related to functional (ergonomic) considerations, and that the way the grammar processes them into surface representations will amount to a reasonable articulatory task for the speaker, while equally the acoustic result will enable the listener to recognise these forms with reasonable ease. However, ultimately we say things the way we do because our lexical representations are the way they are, and our phonological grammar is the way it is.

scholarly journals Ray-Tracing Objects and Novel Surface Representations in CGA

2019 ◽  
pp. 578-584
Author(s):  
Sushant Achawal ◽  
Joan Lasenby ◽  
Hugo Hadfield ◽  
Anthony Lasenby
Keyword(s):  
Ray Tracing ◽  
Surface Representations

scholarly journals Evaluating the potential of post-processing kinematic (PPK) georeferencing for UAV-based structure- from-motion (SfM) photogrammetry and surface change detection

2019 ◽  
Vol 7 (3) ◽  
pp. 807-827 ◽  
Author(s):  
He Zhang ◽  
Emilien Aldana-Jague ◽  
François Clapuyt ◽  
Florian Wilken ◽  
Veerle Vanacker ◽  
...  
Keyword(s):  
Change Detection ◽  
Structure From Motion ◽  
Low Cost ◽  
Post Processing ◽  
Positional Accuracy ◽  
Surface Change ◽  
Ground Control Points ◽  
Single Lens ◽  
Surface Representations ◽  
Uav Images

Abstract. Images captured by unmanned aerial vehicles (UAVs) and processed by structure-from-motion (SfM) photogrammetry are increasingly used in geomorphology to obtain high-resolution topography data. Conventional georeferencing using ground control points (GCPs) provides reliable positioning, but the geometrical accuracy critically depends on the number and spatial layout of the GCPs. This limits the time and cost effectiveness. Direct georeferencing of the UAV images with differential GNSS, such as PPK (post-processing kinematic), may overcome these limitations by providing accurate and directly georeferenced surveys. To investigate the positional accuracy, repeatability and reproducibility of digital surface models (DSMs) generated by a UAV–PPK–SfM workflow, we carried out multiple flight missions with two different camera–UAV systems: a small-form low-cost micro-UAV equipped with a high field of view (FOV) action camera and a professional UAV equipped with a digital single lens reflex (DSLR) camera. Our analysis showed that the PPK solution provides the same accuracy (MAE: ca. 0.02 m, RMSE: ca. 0.03 m) as the GCP method for both UAV systems. Our study demonstrated that a UAV–PPK–SfM workflow can provide consistent, repeatable 4-D data with an accuracy of a few centimeters. However, a few flights showed vertical bias and this could be corrected using one single GCP. We further evaluated different methods to estimate DSM uncertainty and show that this has a large impact on centimeter-level topographical change detection. The DSM reconstruction and surface change detection based on a DSLR and action camera were reproducible: the main difference lies in the level of detail of the surface representations. The PPK–SfM workflow in the context of 4-D Earth surface monitoring should be considered an efficient tool to monitor geomorphic processes accurately and quickly at a very high spatial and temporal resolution.

Freeform surface descriptions. Part II: Application benchmark

2017 ◽  
Vol 6 (5) ◽  
Author(s):  
Anika Broemel ◽  
Chang Liu ◽  
Yi Zhong ◽  
Yueqian Zhang ◽  
Herbert Gross
Keyword(s):  
Design Optimization ◽  
Influencing Factors ◽  
Design Process ◽  
Boundary Function ◽  
Optical Systems ◽  
Freeform Surface ◽  
Surface Description ◽  
Surface Representations ◽  
The Right

AbstractOptical systems can benefit strongly from freeform surfaces; however, the choice of the right representation is not trivial, and many aspects must be considered. Many possibilities to formulate the surface equations in detail are available, but the experience with these newer representations is rather limited. Therefore, in this work, the focus is to investigate the performance of several classical descriptions as well as one extended freeform surface description in their performance in concrete design optimization tasks. There are different influencing factors characterizing the surface representations, the basic shape, the boundary function, the symmetry, a projection factor, as well as the deformation term describing higher order contributions. We discuss some possibilities and the consequences of describing and using these options with success. These surface representations were chosen to evaluate their impact on all these aspects in the design process. As criteria to distinguish the various options, the convergence over the polynomial orders, as well as the quality of the final solutions, is considered. As a result, recommendations for the right choice of freeform surface representations for practical issues in the optimization of optical systems can be given under restrictions of the benchmark assumptions.

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