Papers by Keyword: Ray-Tracing

Abstract: Daylighting simulation programs use different methods and algorithms for illuminance calculations in buildings. It is widely known that results of different lighting simulation programs does not have to be the same for two or more identical rooms. Hence CIE issued Technical Report 171: 2006 which presents test cases to assess the accuracy of lighting computer programs. However, these test cases are simple and the accuracy of daylighting computer programs can be different for more complex cases. The purpose of this paper is a comparison of differences in the results computed by various daylighting simulation programs for selected test cases according to CIE 171: 2006 and for more complex cases.

Abstract: With the progress of the SAR technology, the resolution of SAR image has enhanced constantly. The characteristics of the structure is starting to look increasingly apparent. The simulating to the structures’ characteristics of SAR image can helps people access to the target information which is contained in SAR image easily in complex cases. This paper presents a simulation based on model-cutting, combined with the technique of ray-tracing to simulate the typical SAR image characteristics of target structures of the city. For example, layover, shadow, and other major features such as secondary scattering. This method can effectively simulate typical SAR image plane of the structure, and without regard to the specific physical imaging mechanism itself, is a simple and effective manner SAR image simulation methods.

Abstract: Small angle neutron scattering (SANS) analysis using ellipsoidal neutron mirrors are highly demanded for basic researches of high tensile strength steel sheets, proteins and polymer materials. Although the mirror was conventionally assembled from multilayer neutron super mirrors deposited on ground and polished glass segments, it was difficult to align segmented mirrors with high accuracy and it took several months for the grinding and polishing process. An optimized manufacturing process is proposed utilizing optical function evaluation based on measured mirror surface profile. Optical aberration caused by surface form error and misalignment is evaluated by ray-tracing using mirror surface profile measured by non-contact high precision profilometer.

Abstract: In order to enhance the signal intensity of VLC-LED receiver, this paper describes a receiver condenser which is designed based on optimized CPC (compound parabolic concentrator) by using a truncated method, for achieving the aim of boosting receiver’s ability of gathering light and enhancing signal intensity. The Monte Carlo-ray tracing simulation results shows that in the VLC-LED system, the optimized CPC condenser has those advantages, such as higher concentration ratio, larger concentrate light deviation angle.

Abstract: Daylighting design of buildings is a neglected discipline of building physics, although it is an important element of a healthy indoor environment, since daylight influences the well being of every living being inhabiting a space inside and outside of buildings. It influences the biological rhythms of humans and also enables a visual feedback from the surroundings. To evaluate daylighting inside of buildings one may use any of the available numero-graphical or numerical approaches as much as computer tools. Nevertheless one does not know how precise these methodologies really are. The values of sky, externally and internally reflected components of the obtained daylight factor may vary depending on the given tool, used. To prevent such errors CIE did publish a technical report for the validation of computer design tools, howbeit it can be used to verify the quality of older methods too. The aim of the paper is to point out, that numero-graphical approaches can sometimes determine the daylight factor levels with a smaller errata in contrast to newly developed software, particularly if it handles about the sky and externally reflected components of daylight factor.

Abstract: This study explores the optimum design of secondary optical element (SOE) for a non-coplanar two-reflector solar concentrator. The non-coplanar solar concentrator comprises a primary parabolic mirror and a secondary hyperbolic mirror. Ray tracing simulation is adopted to investigate the optical performance, including the acceptance angle and the optical efficiency, of the solar concentrator with various designs of SOE. Finally, preliminary optimum designs of SOE are presented and discussed.

Abstract: Realistic graphics for virtual reality system has been a hot research at home and abroad, the illumination model mapping and its application of the algorithms is one of the key level to achieve realistic scenes. This paper introduced the illumination model mapping and classification of the algorithms, focused on ray tracing algorithms and bounding box technology of the global illumination model which were realized in the oilfield virtual reality system and have been achieved good results.

Abstract: In this paper, a CAD system is presented for the design, evaluation and simulation of Luneburg lenses. Since this system focuses on high-frequency spherical antenna design and simulation, electromagnetic waves are replaced by rays. A ray-tracing subroutine is employed to trace ray paths and compute phase variations along rays. In traditional CAD systems, the performance of a Luneburg lens is measured by using numerical algorithms, which are difficult to implement and require tremendous computational efforts. In the proposed system, the effectiveness of the target lens is evaluated solely by using the theory of Geometrical Optics (GO). Ray paths and wavefronts are rendered and displayed to show the directivity and focus characters of the lens. The ray phases along with ray paths are also illustrated in graphical media so that the gain and reflectivity of the lens can be predicted.

Abstract: In this work, irradiation distribution on the base of ideal two-dimensional CPCs with and without a restricted exit angle, to which solar cells are attached, are analyzed by the ray-tracing technique. Results show that, given an acceptance half-angle (Θ_a), for CPCs without a restricted exit angle (CPC-1), radiation flux distribution on the base depends on the incidence angle of solar rays (Θ ); whereas for CPCs with a restricted exit angle (CPC-2), the flux distribution depends on and the restricted exit angle (Θ_e). For both CPC-1 and 2 with identical geometric concentration factor (Ct=2) and acceptance half-angle ( Θ_a=20), the peak flux concentration ratio on the base of CPC-2 with =65o decreases about 43%, 30% and 49% for the radiation at the incident angle of 0o, 10o and 18o, respectively, as compared to CPC-1. This implies that solar flux distribution on the base of CPC-2 is more uniform, thus, more efficient for photovoltaic conversion as compared with CPC-1.

Abstract: X-ray radiography has more and more application value and X-ray simulation system has practical significance for improving the quality of X-ray imaging and replacing the expensive devices but it’s a time-consuming work. This paper proposes an improved fast ray-tracing method extended from Siddon’s and Zhao’s methods. For a 2D array, we compute level by level which has natural modes, by comparing the incident x-coordinate with the characteristic constant. In the case of 3D models, the volume data are back projected into 1D linked list and compute indices and lengths similarly like the case of 2D. Compared with Zhao’s method, the new method avoids skipping parametric planes and computing several starting voxels and ending voxels in one level. The time consumed in the new algorithm has reduced by 5/6 regarding the conventional Siddon’s algorithm.