Raster Techniques Research Articles

Mathematical Approach for the Determination of the Surface Roughness in the Milling of Poly-Ether-Ether-Cethone (PEEK)

This research aims to determine the behavior of the surface roughness parameters Ra, Rq and Rz in the milling of poly-ether-ether-ketone PEEK, in terms of the machining variables: cutting speed feed rate and the machining strategy. To solve this problem, a response surface study was made with a central design composed of three replicates per point to obtain a surface equation that determines the expected roughness value based on the velocity values of Cutting speed and fate rate. This model was repeated for each machining strategy analyzed: Raster and Spiral. To find the correct values of Rq and Rzin, the manufacturer could find desirable values; it could be for minor friction pieces or better shape forms. This investigation found that the value of Rq and Rz in milling machining with a Raster and Spiral trajectory increases with increasing feed rate and decreasing with cutting speed. Likewise, it was observed that the Raster technique obtains higher roughness values than by Spiral.

Assessment the Quality of Life in Karachi City through the Integration of Space and Spatial Technologies

This study is an attempt to map and measure the quality of life in the urban area of Karachi, Pakistan, by using Landsat-7 sensor, Enhanced Thematic Mapper (ETM+) combined with Census data through the state-of-the-art Geographic Information System (GIS). For this purpose, the physical environment of the city is determined by the variables of Normalized Difference Vegetation Index (NDVI), surface temperature and land cover/use. These are extracted from the satellite image data through various techniques of remote sensing. On the other hand, the socioeconomic variables were obtained from the 2000 Karachi District Census Reports, to represent the living environment of the city. Finally, the integration of the physical variables with the socioeconomic variables was conducted in a GIS framework using an aggregated Z Sum score approach, in order to derive the quality of life scores for the city of Karachi on the basis of Administrative-Spatial Units called Union Councils (UCs). The results effectively demonstrated the efficiency of the Index raster techniques to evaluate and map the quality of life over the study area. In addition, the GIS techniques also isolated the contributing variables that may be responsible for the spatial variability in the quality of life.

Rendering transparent objects with caustics using real-time ray tracing

After the release of the NVIDIA RTX platform, ray tracing methods are available in real-time rendering and improves the render quality. Therefore, realistic results can be produced in real time by combining ray tracing with rasterization techniques. However, rendering transparent objects with roughness and caustics in real time is still a challenge. We focus on these points and propose a model to render transparent objects based on real-time ray tracing. The model consists of two parts: Iterative Ray Tracing Transparency (IRTT) and Light Half Path Caustics (LHPC). IRTT approximates accurate reflections and refractions by tracing rays, computes volumetric absorption using the length that a ray propagates inside a transparent object, and simulates the rough transparency by bending the normal vector. Meanwhile, LHPC approximates caustics with a method named Local Light Tracing (LLT), where the main task is finding the point of incidence by tracing rays in the direction of the light source. After, a denoiser assisted by a distribution method is applied to suppress the noise. In the experiments, we design a combined pipeline and compare it with our model in terms of performance and render quality. In addition, our results are also compared with rasterization techniques. The experimental results reveal that our model improves the quality of the rendered image and offers a playable framerate.

Comparative study of high performance software rasterization techniques

Comparative study of high performance software rasterization techniques

A resistor network simulation model for laser-scanning photo-current microscopy to quantify low conductance regions in organic thin films

Organic field effect transistors (OFETs) show considerable variation from device to device and batch to batch. For the basic understanding of the microscopic origins of these variations, it is crucial to develop both experimental and theoretical methods that allow to localize ineffective regions in a device. Raster techniques, which manipulate conductivity locally, combined with global current readout may provide this information, e.g. it has been suggested that diffraction limited illumination of OFETs by laser scanning photo-current microscopy provides trap density distribution maps. However, the question arises whether local variation of conductivity is indeed suited for localization of such defects given that the detected photo-current passes through the whole network of conductance in the thin film device. In this study, we present a simulation model based on resistor networks to investigate the effect of defective regions in organic thin films. We show that varying conductances locally allows indeed to reconstruct the spatial distributions of ineffective areas. We also demonstrate how such simulations can be applied to interpret photo-current microscopy maps in terms of trap densities.

Polymineralic inclusions in mantle chromitites from the Oman ophiolite indicate a highly magnesian parental melt

Polymineralic inclusions interpreted as melt inclusions in chromite from the dunitic Moho Transition Zone in the Maqsad area of the Oman ophiolite have been analysed and compositions integrated using a rastering technique on the scanning electron microscope. The inclusions now comprise a range of inter-grown hydrous phases including pargasite, aspidolite, phlogopite and chlorite, indicating that the parental melts were hydrous. Average inclusion compositions for seven samples contain between 23.1 and 26.8 wt% MgO and 1.7–3.6 wt% FeO. Compositions were corrected to allow for the low FeO concentrations using coexisting olivine compositions. These suggest that the primary melt has between 20 and 22 wt% MgO and 7–9.7 wt% FeO and has an affinity with boninitic melts, although the melts have a higher Ti content than most boninites. Average rare earth element concentrations suggest that the melts were derived from a REE depleted mantle source although fluid-mobile trace elements indicate a more enriched source. Given the hydrous nature of the inclusions this enrichment could be fluid driven.An estimate of the melt temperature can be made from the results of homogenisation experiments on these inclusions and suggests ~1300 °C, which implies for a harzburgite solidus, relatively shallow melting at depths of <50 km and is consistent with a boninitic origin.The current “basaltic” nature of the chromite host to highly magnesian melt inclusions suggests that the dunitic Moho Transition Zone operated as a reaction filter in which magnesian melts were transformed into basalts by the removal of high magnesian olivines, particularly in areas where the Moho Transition Zone is unusually thick. We propose therefore that podiform mantle chromitites, even those with an apparent MORB-like chemical signature, have crystallised from a highly magnesian parental melt. The data presented here strongly support the view that this took place in a subduction initiation setting.

PROCESSING UAV AND LIDAR POINT CLOUDS IN GRASS GIS

Abstract. Today’s methods of acquiring Earth surface data, namely lidar and unmanned aerial vehicle (UAV) imagery, non-selectively collect or generate large amounts of points. Point clouds from different sources vary in their properties such as number of returns, density, or quality. We present a set of tools with applications for different types of points clouds obtained by a lidar scanner, structure from motion technique (SfM), and a low-cost 3D scanner. To take advantage of the vertical structure of multiple return lidar point clouds, we demonstrate tools to process them using 3D raster techniques which allow, for example, the development of custom vegetation classification methods. Dense point clouds obtained from UAV imagery, often containing redundant points, can be decimated using various techniques before further processing. We implemented and compared several decimation techniques in regard to their performance and the final digital surface model (DSM). Finally, we will describe the processing of a point cloud from a low-cost 3D scanner, namely Microsoft Kinect, and its application for interaction with physical models. All the presented tools are open source and integrated in GRASS GIS, a multi-purpose open source GIS with remote sensing capabilities. The tools integrate with other open source projects, specifically Point Data Abstraction Library (PDAL), Point Cloud Library (PCL), and OpenKinect libfreenect2 library to benefit from the open source point cloud ecosystem. The implementation in GRASS GIS ensures long term maintenance and reproducibility by the scientific community but also by the original authors themselves.

PROCESSING UAV AND LIDAR POINT CLOUDS IN GRASS GIS

Today’s methods of acquiring Earth surface data, namely lidar and unmanned aerial vehicle (UAV) imagery, non-selectively collect or generate large amounts of points. Point clouds from different sources vary in their properties such as number of returns, density, or quality. We present a set of tools with applications for different types of points clouds obtained by a lidar scanner, structure from motion technique (SfM), and a low-cost 3D scanner. To take advantage of the vertical structure of multiple return lidar point clouds, we demonstrate tools to process them using 3D raster techniques which allow, for example, the development of custom vegetation classification methods. Dense point clouds obtained from UAV imagery, often containing redundant points, can be decimated using various techniques before further processing. We implemented and compared several decimation techniques in regard to their performance and the final digital surface model (DSM). Finally, we will describe the processing of a point cloud from a low-cost 3D scanner, namely Microsoft Kinect, and its application for interaction with physical models. All the presented tools are open source and integrated in GRASS GIS, a multi-purpose open source GIS with remote sensing capabilities. The tools integrate with other open source projects, specifically Point Data Abstraction Library (PDAL), Point Cloud Library (PCL), and OpenKinect libfreenect2 library to benefit from the open source point cloud ecosystem. The implementation in GRASS GIS ensures long term maintenance and reproducibility by the scientific community but also by the original authors themselves.

Direct e-beam writing of colors on (AgI)x(AgPO3)1−x glass

Direct writing of color patterns is investigated in (AgI)x(AgPO3)1−x ionically conductive glasses through the use of an electron beam. A range of glasses from x = 0–0.5 are explored to represent varying levels of ionic conductivity and the gamut of colors possible depending on substrate composition. For AgIAgPO3, writing capabilities are found to include a linear, tunable optical density of patterns in transmission, as well as diffraction limited color resolution in reflection. Writing at multiple currents, beam energies, and raster techniques are performed to explore the sensitivity to variations of process parameters. With advanced multiple beam voltage patterning techniques, the authors demonstrate the capability to both generate new colors as well as erase patterns previously created with this process.

Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures.

2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices.

Automatic detection of zebra crossings from mobile LiDAR data

Abstract An algorithm for the automatic detection of zebra crossings from mobile LiDAR data is developed and tested to be applied for road management purposes. The algorithm consists of several subsequent processes starting with road segmentation by performing a curvature analysis for each laser cycle. Then, intensity images are created from the point cloud using rasterization techniques, in order to detect zebra crossing using the Standard Hough Transform and logical constrains. To optimize the results, image processing algorithms are applied to the intensity images from the point cloud. These algorithms include binarization to separate the painting area from the rest of the pavement, median filtering to avoid noisy points, and mathematical morphology to fill the gaps between the pixels in the border of white marks. Once the road marking is detected, its position is calculated. This information is valuable for inventorying purposes of road managers that use Geographic Information Systems. The performance of the algorithm has been evaluated over several mobile LiDAR strips accounting for a total of 30 zebra crossings. That test showed a completeness of 83%. Non-detected marks mainly come from painting deterioration of the zebra crossing or by occlusions in the point cloud produced by other vehicles on the road.

An Efficient Rasterization Unit With Ladder Start Tile Traversal in 3-D Graphics Systems

To render 3-D graphics efficiently, rasterization techniques have been developed. Traditional triangle traversal techniques using scan-line-based or edge-equation-based methods may cause potential instability from the division operations. This paper develops an efficient rasterization algorithm-a barycentric-based ladder start tile traversal that is division free. Throughout the process, no extra traversal position and context is produced to reduce the number of pixel tests and improve the efficiency and stability of the graphic rendering. It also presents the architecture of a 300 MHz 3-D graphics rasterizer in a 65 nm 1P9M process with a core size of 0.537 mm\(^{2}\) and internal buffer 3 K. The proposed ladder start tile traversal architecture can perform each tile intersect test in six cycles and tile interior traversal with barycentric tests in 2 pixels per cycle. In addition, the rasterizer throughput can achieve up to 50M triangles per second and 600M pixels per second.

3-D graphics processor unit with cost-effective rasterization using valid screen space region

In order to render 3-D graphics efficiently, rasterization techniques have been developed. Traditional clipping techniques using six-planes of view volume are complicated and not cost-effective. This paper develops a novel cost-effective strategy for primitives with regard to clipping in rasterization. Throughout the process, no expensive clipping action is required and no extra clipping-derived polygons are produced. It also presents the architecture of a 200-MHz multicore, multi-thread 3-D graphics SoC in 65nm 1P9M process with a core size of 4.97mm2 and 153.3mW for power consumption. The proposed clip-less architecture in rasterization processes the valid screen space region of each primitive in eight cycles, with a gate-count of only 20k. In addition, the throughput can achieve up to 25 M Triangles/Sec.

Accessible volume in quenched-annealed mixtures of hard spheres: a geometric decomposition

Model systems in which fluid particles move in a disordered matrix of immobile obstacles have been found to be a reasonable representation of a colloidal fluid confined in a disordered porous medium. For systems consisting of hard-sphere particles, the obstacle matrix partitions the space available to the fluid particles into voids of finite volume (‘traps’) and a percolating void that extends over the entire volume. This geometric distinction plays a key role for the dynamic properties of the confined fluid: while its particles are not able to escape from traps, in the percolating void they can propagate infinitely far. We present a geometric method, based on a Delaunay decomposition, to identify the two different kinds of voids in an arbitrary matrix configuration of finite size under periodic boundary conditions. We subsequently apply a rastering technique, which enables us to statistically characterize the structure of the voids. We investigate the specific case of a quenched-annealed mixture of identical hard spheres, for which, among others, we accurately determine the matrix packing fraction at which the percolation transition of the voids takes place.

News Briefs

German researchers have developed a chip that can render complex graphics in real time. The chip could allow individuals or small organizations to easily perform complex graphics work. Currently, they must either use a single computer, which takes a long time to produce sophisticated graphics, or they must spend the money to have a cluster of computers yield results quickly. Saarland University scientists have developed an algorithm that lets a chip rapidly perform ray tracing. This approach is an alternative to the rasterization techniques - used in most of today's graphics chips - that convert mathematical and digital information into a matrix of pixels. Ray tracing is a sophisticated approach that renders images in 3D environments by tracing the paths that light rays would take through a scene and calculating the reflection, refraction, or absorption that would occur when they hit an object. Unlike rasterization, ray tracing yields the information needed to compute shadows, reflections, and other effects necessary for high-quality images

Rasterizing complex polygons without tessellations

Rasterization of polygons is a basic operation in computer graphics systems, representing the last and most time-consuming step in the visualization process. Therefore, the development of simple, efficient, and general polygon rasterization techniques is of prime interest. In this paper, we describe a new algorithm for this purpose, inspired on the ideas of the geometric modeling based on simplicial chains [Computer and Graphics 5 (1998) 611]. This algorithm is valid for any kind of polygon, is robust and extremely simple, and can be easily implemented in hardware. A similar approach can be used for the problem of polihedra voxelization in 3D.

A virtual memory architecture for real-time ray tracing hardware

Real-time ray tracing offers a number of interesting benefits over current rasterization techniques. However, a major drawback has been that ray tracing requires access to the entire scene data base. This is particularly problematic for hardware implementations that only have a limited amount of dedicated on-board memory. In this paper we propose a virtual memory architecture for ray tracing that efficiently renders scenes many times larger than the available on-board memory. Instead of wasting large dedicated memory on a graphics card, scene data is stored in main memory, and on-board memory is used only as a cache. We show that typical scenes from computer games only require less than 8 MB of cache memory while 64 MB are sufficient even for scenes with GBs of geometry and textures. The caching approach also minimizes the bandwidth between the graphics subsystem and the host such that even a standard PCI connection is sufficient.

On the Fresnel diffraction pattern of phase holographic gratings

The Fresnel diffraction pattern of phase diffraction gratings is studied on the example of idealized sinusoidal relief-phase plane holographic thermoplastic gratings. It is shown that, in the region of low spatial frequencies, which are more than two times lower than the inverse wavelength of the reading coherent radiation, the intensities of the main diffraction maxima, the diffraction efficiency, and the light-scattering power are independent of the spatial frequency of the phase gratings under investigation, which are characterized by a sinusoidal law of modulation of the reading-radiation phase. It is established that the range of spatial frequencies at which a plateau is observed in these dependences increases with decreasing amplitude of the phase modulation of the reading light. These dependences are also observed to have similar character for the thermoplastic holographic gratings under study. Calculations were performed to analyze the influence of real profiles of thermoplastic strain on the diffraction efficiency and light-scattering power of such gratings. On the basis of analysis of the results obtained, recommendations on using holographic and raster techniques of recording data on phase carriers are given that make it possible to improve the quality of the restored optical image.

Mapping health events - a comparison of approaches

The Waikato Regional Public Health Unit (New Zealand) collects and maintains a database of notified health events that includes communicable diseases. This database can be used by health protection officers to identify problem areas that have unusually high incidences of events. Resources can then be targeted and officers can respond accordingly. However, for this data to be useful it needs to be represented as a rate of health events per 100,000 people. This paper investigates the use of Geographic Information Systems (GIS) to visualize and represent these data. Standard vector representations that use census area units are compared with raster representations that use focal neighbourhood functions. The two techniques produce rates of health events that differ by up to 100 per cent for a given location and scale. The vector technique is the standard approach and is easily understood. The raster technique enables more control over the scale of analysis and can provide a more spatially accurate representation of health events. If two techniques can produce such large differences in analysis results, it is important that health protection officers and epidemiologists give special consideration to the representation technique used.

Visualizing point sets, fractals, and quasicrystals using raster techniques

Algorithms for creating a natural Voronoi tiling associated with point sets are developed. These algorithms provide additional information about the tiling which can be readily visualized. Images created in this way can be quite striking. We illustrate the application of the algorithms on fractals, lattices, and quasicrystals.