Graphical Ray Tracing Research Articles

Analysis of tracking characteristics of a heliostat field using a graphical ray tracing procedure

The tracking requirements of all heliostats in a field are not the same, and they vary according to day, time, and latitude. In this work, a graphical ray tracing (GRT) based model is developed and demonstrated with two-axis Azimuth-Elevation (AE) and Spinning-Elevation (SE) tracking techniques. The procedure is simple and obviates the complex rotation-matrices formulation reported in the previous literature. Using the GRT, a new Center-Oriented Spinning-Elevation (COSE) tracking technique is proposed and demonstrated in which, instead of at the target, heliostats are pointed towards the on-field center-point of the tower. Tracking based on this co-ordinate system results in a substantial reduction in rotations of tracking motors and parasitic-energy of heliostats. Motion analysis of eight heliostats placed at different on-field locations and distances from the tower are conducted, and their tracking characteristics are explained in detail with respect to time, latitude, and tracking modes. The effect of on-field position and distance is presented with fast-tracking requirements and reflected mirror images on the receiver plane. The COSE method obtains a better shape of the reflected-image with less aberration on the receiver plane than SE and AE methods. The analysis performed in this work addresses the trade-off between tracking speed and cost while designing a tracking system for heliostat field.

Simulation of Radio Signal Propagation for UHF RFID Technology in an Indoor Environment Using Ray Tracing (Graphics) Method

RFID systems are often used in industry to reduce costs, increase process efficiency and minimize human intervention. The challenge is to design an RFID system before it is implemented in a specific environment in the shortest possible time and at minimum cost while maintaining the accuracy of the results. In this paper, a new approach to predicting indoor UHF RFID signal coverage is presented. It is based on a graphical ray tracing method. Simulations are performed based on spatial analysis of the illumination of a 3D indoor environment created from a 2D floor plan. The results show a heat map representing the predicted RSSI radio signal levels using a color range. The approach is validated by comparison with the results of the empirical Multi-Wall model. The time complexity of the approach is presented. The proposed approach is able to generate a heat map with the accuracy of the empirical Multi-Wall model. The interior room equipment required to refine the results ought to be investigated in the future.

Graphical Ray Tracing Formulation of New Center Oriented Spinning Elevation Tracking Technique for Heliostat

Graphical Ray Tracing Formulation of New Center Oriented Spinning Elevation Tracking Technique for Heliostat

Center-Oriented Aiming Strategy for Heliostat With Spinning-Elevation Tracking Method

Abstract Spinning-elevation (SE) tracking system produces a decent image on the receiver surface; however, it is subjected to large variations in tracking speed. In this research, a graphical ray tracing (GRT) model for center-oriented spinning-elevation (COSE) tracking method is developed to evaluate tracking angles. Instead of a target, a heliostat is pointed toward the on-field center point of the tower. Therefore, a spinning-axis of rotation is a line joining a heliostat, and a center of the tower and elevation-axis is perpendicular to it. This aiming strategy has shown a substantial reduction in rotations of spinning-motor. In contrast, the elevation-motor runs at slightly higher rotations than the target-oriented SE method for the same application. Also, COSE tracking method obtains better shape of the reflected image with less aberration on the receiver surface as compared with SE and the traditional Azimuth-elevation (AE) method.

Performance Enhancement of CPC Using Graphical Ray Tracing

This paper presents the approach of finding an optimized location of a tubular receiver for a compound parabolic collector (CPC) with 23.06° acceptance angle. At this angle reflected rays concentrate at and directly above the main focus of a parabola. Ray tracing plays vital role in analysing rays falling on collector surface and reflected to the receiver. Using this analysis, solar collectors are often designed or improved to enhance the thermal performance. As compound parabolic collectors (CPC) are non-imaging kind and positioned in E-W direction, they are capable of assembling and reflecting an enormous quantity of radiation to the receiver with least tracking. Ray tracing technique was used to evaluate the performance of CPC. A graphical ray tracing (GRT) with SolidWorks was employed to observe the pattern of solar ray concentration. The main aim was to design CPC for low to medium temperature thermal process heat applications, specifically for Textile industries. It is observed that over one tubular absorbers will work better for CPC to absorb most solar rays and two tubular receivers lined up horizontally enhanced the CPC daily average optical efficiency by up to 15-20% compared to the single tubular receiver with the same diameter. Ray-Tracing analysis would possibly provide necessary contributions to beat design problems, complementing the experimental results obtained through thermal testing and allowing the accomplishment of extra thorough testing outputs with lower experimental requirements.

Occlusion calculation algorithm for computer generated hologram based on ray tracing

Computer-generated holograms(CGHs) with occlusion information have a better sense of reality. There is also a reduction in the amount of calculation since the occluded part does not need to be calculated. We made adaptive changes to the traditional graphical ray tracing method and introduced it into CGH to get the correct occlusion effect of point cloud models and achieve fast intersection calculation. To realize the motion parallax effect, the hologram is divided into sub-holograms. A KD-Tree traversal algorithm for a GPU based on the virtual stack is proposed to implement efficient parallel computation in ray tracing. The effectiveness of the proposed algorithm was verified by several experiments in terms of the occlusion effect and motion parallax effect, and its temporal and spatial efficiency was proven.

Design configurations and possibilities of reflector shape for solar compound parabolic collector by ray tracing simulation

The objective of this paper is to study various possible configurations of reflectors of the compound parabolic collector (CPC) and select the suitable design as per the requirement. CPC is composed of two parabolic segments which show a wide range of design possibilities with its basic construction. This construction is based on design parameters like acceptance angle, rim angle, parabolic segments, truncation of parabolas, and location of the focus point and concluded for the suitable end application. A graphical ray tracing (GRT) simulation is used to examine the pattern of solar ray concentration for each design possibility. The various reflector configurations are generated from the design-morphological chart and compared on the basis of region and density of ray’s concentration. The research emphasizes a novel approach of constructing a CPC with possible design configurations which can find a great scope for further research. The various configurations would help engineers to select and design a CPC as per the requirement.

Evaluation and optimisation of receiver height in a compound parabolic collector with low acceptance angle

ABSTRACTThis research presents the method of finding an optimised location of a tubular receiver for a compound parabolic collector (CPC) with 6° acceptance angle. Due to low acceptance angle, reflected rays concentrate below the focus of a parabola. Graphical ray tracing (GRT) approach is implemented to execute the optical analysis with and without manufacturing error in the collector. It is performed on collector–receiver combinations by varying receiver height below the focus and they are compared on the basis of utilised area and projection ratios. The ideal cases of collector–receiver combinations which contribute high utilisation and projection ratio are selected and verified with the camera target method (CTM) performed on the actual set-up. It is built for water heater application to validate the results obtained from GRT and CTM. The thermal performance of CPC at various receiver heights is compared by thermal efficiency and therefore the optimum receiver height is concluded.

Optimization of receiver height in compound parabolic collector by optical analysis and experimental method

The paper presents the method of finding an optimized location of a tubular receiver for the compound parabolic collector (CPC) with a low acceptance angle of 6°. Due to low acceptance angle, the reflected rays concentrate below the common focus of parabola in a definite pattern. Graphical ray tracing approach (GRT) is implemented to execute the optical analysis with and without manufacturing error in a parabolic shape. This analysis is performed on the collector – receiver combinations by varying receiver height below the focus and they are compared on the basis of the utilized area for collector and receiver and projection ratios. The ideal cases in which the collector – receiver combinations contribute a high utilization and projection ratio are selected and verified with the observations of camera target method (CTM) performed on the actual CPC set-up. This set-up is built for a water heater application to validate the results obtained from the GRT and CTM observations. Surface areal irradiance (SAI) method is used to determine the net heat added to the receiver at different heights. The optimum height at which the CPC performed with higher thermal efficiency is concluded as the best location for the tubular receiver for the presented CPC.

Optical evaluation of compound parabolic collector with low acceptance angle

An optical evaluation improves overall performance of solar collectors by minimizing the optical losses. It includes study and analysis of solar rays and its behavior when falling and reflecting over collectors. As per collector design criteria, the maximum collection of solar rays must concentrate at the receiver. In this research, the optical analyses are performed on compound parabolic collector with low acceptance angle (6°) to optimize the receiver position. In parabolic trough collector (PTC), all the reflected solar rays gather at the focal line, but in CPC the reflected solar rays concentrates in a region on the central plane. This region of concentrated solar rays is determined by 2D graphical ray tracing analysis and it is experimentally verified by camera target method (CTM). The manufacturing error in collector shape is elaborated and error curve is outlined with the help of data points. The ray tracing analysis is performed on the actual and error curve with the incidence angle 0°, +3° and −3°. and it is compared with CTM observations. The results obtained from these methods showed the identical behavior of reflected solar rays and it is concentrated below the limiting diameter at the focus.

Experimentation of surface areal irradiance method for solar flux measurement in compound parabolic collector

Flux measurement is one of the major considerations in the optical analysis of solar collector to improve its performance. An uneven distribution of concentrated solar rays at the receiver creates the need of finding a region of high concentration flux and its measurement. This paper describes the experimentation of the author’s recent study of surface areal irradiance (SAI) method performed on compound parabolic collector (CPC) with low acceptance angle. This method uses a 2D graphical ray tracing techniques to determine the region of high concentration of solar flux and its intensity in that region. Also the present study refines the concept of SAI method with geometric cosine factors for incident and reflected rays. The result of flux curves by SAI method and experimentation show the identical characteristics and it is plotted along with solar direct irradiation and variable collector area. SAI method uses the reflector area instead of aperture area to determine concentrated flux which is helpful in designing solar collectors as per the requirements.

Flux concentration on tubular receiver of compound parabolic collector by surface areal irradiance method of ray tracing

Ray tracing for solar collectors finds wide application for designing the components. In this research, a solar flux concentration on the tubular receiver of compound parabolic collector (CPC) is determined by a novel approach of surface areal irradiance (SAI). The objective of this method is to determine the solar reflected irradiance at the receiver by incorporating effective areas of reflector and receiver. These areas are determined by 2D graphical ray tracing technique. Multiple ray tracing iterations are performed on various geometric possibilities of receiver–collector combinations by varying receiver diameter and height. The collector dimensions are fixed as per authors previously designed CPC to reduce the number of possibilities of receiver – collector combinations. The results of these iterations are presented in terms of utilization ratio (U), projection ratio (P) etc. based on which concentrated solar flux and heat equations are determined. It is observed that there is saturation point for all receiver diameters at which a receiver – collector combination gives highest utilization ratio and the corresponding height gives the best location for that receiver. SAI method gives a strong methodology for designing solar collectors on the basis of utilization ratios and heat equations.

Shell: A Spatial Decomposition Data Structure for Ray Traversal on GPU

Shared memory many-core processors such as GPUs have been extensively used in accelerating computation-intensive algorithms and applications. When porting existing algorithms from sequential or other parallel architecture models to shared memory many-core architectures, non-trivial modifications are often needed to match the execution patterns of the target algorithms with the characteristics of many-core architectures. Ray traversal is a fundamental process in many applications, and is commonly accelerated by spatial decomposition schemes captured in hierarchical data structures (e.g., kd-trees). However, ray traversal using hierarchical data structures needs to conduct repeated hierarchical searches. Such search process is time-consuming on shared memory many-core architectures since it incurs considerable amounts of expensive memory accesses and execution divergence. In this paper, we propose a novel spatial decomposition based data structure, called Shell, which completely avoids hierarchical search for ray traversal. In Shell, a structure is built on the boundary of each region in the decomposed space, which allows any ray traversing in a region to find the next neighboring region to traverse using table lookup schemes, without any hierarchical search. While our ray traversal approach works for other spatial decomposition paradigms and many-core processors in higher dimensional scenes, we illustrate it using kd-tree on GPU for 3D scenario and compare with the fastest known kd-tree searching algorithms for ray traversal. Experimental results in graphics ray tracing and radiation dose calculation show that our approach improves the performance by 3.5-5.5 $\times$ over the fastest known kd-tree based approaches.

Local Exact Particle Tracing on Unstructured Grids

Abstract For analyzing and interpreting results of flow simulations, particle tracing is a well established visualization method. In addition, it is a preliminary step for more advanced techniques such as line integral convolution. For interactive exploration of large data sets, a very efficient and reliable particle tracing method is needed. For wind channel experiments or flight simulations, large unstructured computational grids have become common practice. Traditional approachs, based on numerical integration methods of ordinary differential equations however fail to deliver sufficiently accurate path calculation at the speed required for interactive use. In this paper we extend the local exact approach of Nielson and Jung in such a way that it can be used for interactive particle tracing in large data sets of steady flow simulation experiments. This will be achieved by sophisticated preprocessing using additional memory. For further visual enhancement of the streamline we construct an implicitly defined smooth Bézier curve that is used for ray tracing. This allows us to visualize additional scalar values of the simulation as attributes to the trajectory and enables the display of high‐quality smooth curves without creating any visualization geometry and providing a good impression of the spatial situation at the same time. ACM CSS: I.3.3 Computer Graphics—Line and curve generation; I .3.7 Computer Graphics—Raytracing; G.1.2 Numerical Analysis—Spline and piecewise polynomial approximation

The art of back-of-the-envelope paraxial raytracing

Paraxial raytracing is a valuable tool for making quick back-of-the-envelope calculations in optical system design. Its popularity has been highly diminished as a consequence of the growing sophistication of computer-aided raytracing and the availability of powerful computers. The availability of raytracing computer programs does not harm in itself the usefulness of graphical raytracing, but it makes people forget, or never learn the basics of graphical raytracing. In this paper, some of the basic concepts of graphical raytracing are presented, along with some examples that illustrate how it can be applied to multielement systems. The mastering of the methods presented in this paper constitute some of the fundamentals required in the use of any optical software. Such knowledge is absolutely necessary for the conception of novel optical systems.

Parallel computing comes of age: Supercomputer level parallel computations at Caltech

AbstractParallel supercomputers are now in regular use at Caltech for several major scientific calculations. We use this experience to abstract a set of lessons for applications, decomposition, performance, hardware and software. We consider hypercubes, transputer arrays and the SIMD Connection Machine CM‐2 and AMT DAP. These are contrasted, where possible, with CRAY and other high performance conventional computers. Applications covered are lattice gauge theory, plasma physics, statistical and condensed matter physics, astronomical data analysis, quantum chemistry, graphics ray tracing, string dynamics, grain dynamics, astrophysical particle dynamics, computer chess and Kalman filters.

Internal brightness of disk-shaped samples

Internal spectral brightness for the front and back layer of planoparallel samples can be measured by using a bipartite ring-shaped cuvette. The inner walls are highly specularly reflecting and enclose samples by means of fluid and windows of the same refractive index as the sample surface. A fibre optic probe, approaching constant spherical responsivity, evaluates the photon fluxes in both compartments of the cuvette. Graphical ray tracing in planoparallel samples serves to derive equations predicting the results of the direct measurements. According to the theory, differently scattering disks of Plexiglass, selected as a series of test materials, show internal photon fluxes for the front layer in the range 1 – 4.6 times that of the externally irradiated flux. Bifacial plant leaves, of Ctenanthe compressa, Philodendron scandens and Kalanchoe marmorata, exhibit internal photon fluxes strongly dependent on leaf morphology and wavelength; in the red at 616 and 672 nm, for the front layer they fall between 1.1 and 1.8 times the irradiated flux, increasing to values between 2.9 and 3.5 times in the far red at 756 nm.

Graphical ray tracing for conic surfaces

Graphical ray tracing for conic surfaces

The influence of collector temperature on the maximum efficiency of a thermionic converter in the series battery

An optical evaluation improves overall performance of solar collectors by minimizing the optical losses. It includes study and analysis of solar rays and its behavior when falling and reflecting over collectors. As per collector design criteria, the maximum collection of solar rays must concentrate at the receiver. In this research, the optical analyses are performed on compound parabolic collector with low acceptance angle (6°) to optimize the receiver position. In parabolic trough collector (PTC), all the reflected solar rays gather at the focal line, but in CPC the reflected solar rays concentrates in a region on the central plane. This region of concentrated solar rays is determined by 2D graphical ray tracing analysis and it is experimentally verified by camera target method (CTM). The manufacturing error in collector shape is elaborated and error curve is outlined with the help of data points. The ray tracing analysis is performed on the actual and error curve with the incidence angle 0°, +3° and −3°. and it is compared with CTM observations. The results obtained from these methods showed the identical behavior of reflected solar rays and it is concentrated below the limiting diameter at the focus.

Determination of focusing properties of solar collectors by an integral formula

Abstract An analytical procedure is derived for determining the distribution of energy at the focal plane of a mirror such as is used in a solar collector system. The method is a general one that permits any shape of emitting and reflecting surfaces, and is an analytical equivalent of the conventional ray-tracing procedure of geometrical optics. The advantage provided is that the calculation of intensity of collected radiation at a given point can be performed on a digital computer in less than 15 seconds whereas one man-week is required for graphical ray tracing. The solution takes the form of an exact double integral which gives directly the intensity of reflected radiation at any given point for an arbitrary Lambert surface emitting at least partially to an arbitrary reflecting surface. The double integral has been programmed on a digital computer to evaluate the performance of solar collectors.