Raytracing

امروزه صنعت پویانمایی سازی یکی از پرطرفدارترین و پر درامد ترین صنعتها محسوب میشود؛ که بخش
بزرگی از اوقات فراغت همه مردم جهان را پرکرده، چه بر روی کامپیوترهای شخصی، چه بر روی کنسولهای
بازی و حتی موبایلها که همجا به همراه داریم. ازاینرو فعالیتهای زیادی در این زمینه صورت میگیرد تا
بازیهای سرگرمکننده و متنوع را ارائه دهند. یکی از تکنیکهایی که تحول بزرگی در این صنعت ایجاد
کرده، تکنیک ردیابی پرتو در بحث تولید تصاویر گرافیکی میباشد. در سالهای گذشته تحقیقات زیادی
مبنی بر بهبود این تکنیک و کاهش زمان پردازش آن صورت گرفته. دغدغه اصلی این تکنیک زمان پردازش
آن نیز میباشد. در تلاشهای صورت گرفته تا جایی توانستهاند این زمان را کاهش دهند، اما باز نتوانستهاند
از حداکثر توان سختافزار برای کاهش این زمان استفاده کنند.در این مقاله به برسی روشهای توزیعشده و
تکی این روشها می پردازیم.

The aim of this thesis is to investigate the applicability of a novel image synthesis technique based on Monte Carlo particle transport to daylight simulation. Many materials used in daylight simulation are specifically designed to redirect light, and as such give rise to complex effects such as caustics. The photon map technique was chosen for its efficent handling of these effects. To assess its ability to produce physically correct results which can be applied to lighting simulation, a validation was carried out based on analytical case studies and on simple experimental setups. As prerequisite to validation, the photon map´s inherent bias/noise tradeoff is investigated. This tradeoff depends on the density estimate bandwidth used in the reconstruction of the illumination. The error analysis leads to the development of a bias compensating operator which adapts the bandwidth according to the estimated bias in the reconstructed illumination.

A computational approach is presented, which uses the finite volume (FV) method in the Computational Fluid Dynamics (CFD) sol-ver ANSYS Fluent to conduct the ray tracing required to quantify the optical performance of a line concentration Concentrated Solar Power (CSP) receiver, as well as the conjugate heat transfer modelling required to estimate the thermal efficiency of such a receiver. A Linear Fresnel Collector (LFC) implementation is used to illustrate the approach. It is shown that the Discrete Ordinates method can provide an accurate solution to the Radiative Transfer Equation (RTE) if the shortcomings of its solution are resolved appropriately in the FV CFD solver. The shortcomings are due to false scattering and the so-called ray effect inherent in the FV solution. The approach is first evaluated for a 2-D test case involving oblique collimated radiation and then for a more complex 2-D LFC optical domain based on the FRESDEMO project. For the latter, results are compared with and validated against those obtained with the Monte Carlo ray tracer, SolTrace. The outcome of the FV ray tracing in the LFC optical domain is mapped as a non-uniform heat flux distribution in the 3-D cavity receiver domain and this distribution is included in the FV conjugate heat transfer CFD model as a volumetric source. The result of this latter model is the determination of the heat transferred to the heat transfer fluid running in the collector tubes, thereby providing an estimation of the overall thermal efficiency. To evaluate the effectiveness of the phased approach in terms of accuracy and computational cost, the novel 2-D:3-D phased approach is compared with results of a fully integrated, but expensive 3-D optical and thermal model. It is shown that the less expensive model provides similar results and hence a large cost saving. The novel approach also provides the benefit of working in one simulation environment, i.e. ANSYS Workbench, where optimisation studies can be carried out to max-imise the performance of linear CSP reflector layout and receiver configurations.

Photorealistic rendering is very often used area in computer graphics. It is used to display human body in medicine, buildings in architecture and also in other areas of our life. For photorealistic rendering are very important powerful computer, than it is relative difficult on computing. To render a 3D object in computer graphics a high efficient computer is needed, which enable user to work with graphic information on higher level. In some cases of data visualization rendering can slow-down the whole proccess of computing. One possibility how to solve this problem is to apply photorealistic rendering on distributed systems. Designed system is outgoing from static assigning and sharing of scene based on areas, so that the time needed for rendering doesn’t affect the whole time. Through this architecture rendering should be more effective according to time in distributed systems.

In the present paper we solve the complex problem posed by the complex motion described by the combination of translation and rotation that can be seen when observing the wheels of a vehicle passing by.. Our paper is divided in two main parts, in the first part, we will derive the relativistic equations for rolling motion without slipping and we will make some connections with the physical requirements of a relativistic raytracing algorithm. In the second part, we will review the foundations of classical raytracing algorithms and we will introduce the additional features for operation at relativistic speeds.

The investigation of space debris involves the characterization of orbital objects, which includes the collection of information like orbit, body shape and attitude. Current studies are mainly concerned with methods for precise orbit determination. However, future removal missions will need additional information of the objects state – in particular the attitude. For this purpose, researchers of the Institute of Technical Physics at the German Aerospace Center (DLR) in Stuttgart, Germany started a new research campaign to investigate light curves of debris objects.

In this paper, we present a physical validation of global illumination algorithms based on measurements from a simple experimental setup. The validation methodology emphasizes tractability and error minimization. To this end, we discuss issues such as the acquisition and accurate simulation of material bidirectional reflection distribution functions (BRDFs) and the light source distribution, as well as error analysis. In addition, we present a nearest-neighbor resampling technique for BRDFs and a simple method for extracting the light source distribution from digitized high dynamic range (HDR) images. Finally, we compare the measurements to a forward and backward raytracing solution (photon map and RADIANCE, respectively) in a set of case studies.

Photon mapping is an efficient method for producing high-quality, photorealistic images with full global illumination. In this paper we present a more accurate and efficient approach to final gathering using the photon map based upon hierarchical evaluation of the photons over each surface. We use the footprint of each gather ray to calculate the irradiance estimate area rather than deriving it from the local photon density. We then describe an efficient method for computing the irradiance from the photon map given an arbitrary estimate area. Finally, we demonstrate how the technique may be used to reduce variance and increase efficiency when sampling diffuse and glossy-specular BRDFs.

The presentation of a recent addition to the suite of popular global illumination rendering methods is the focus of this thesis. The photon map comprises a particle transport simulation with a density estimate characterized by independency of the scene geometry and the ability to efficiently model diffuse global illumination and caustics. Its embedding in existing ray tracing environments is straightforward; an implementation of the photon map and its integration in the Minimal Rendering Toolkit (MRT) is described in detail.

Observations (e.g. Phillips, Heckman et al., Martin) have revealed cold gas with large velocity dispersions (≈300 km s −1) within the hot outflows of ultraluminous infrared galaxies (ULIRGs). This gas may trace its origin to the Rayleigh–Taylor (RT) fragmentation of a super-bubble or may arise on smaller scales. We model a ULIRG outflow at two scales to recreate this gas in three-dimensional hydrodynamic simulations using FLASH. Although resolution is limited, these models successfully produce cold gas in outflows with large velocity dispersions. Our small-scale models produce this cold gas through RT fragmentation of the super-bubble wall, but the large-scale models produce the cold gas after hot bubbles fragment the disc's gas into cold clouds which are then accelerated by thermal pressure, and supplemented by cooling within the outflow. We produce simple mock spectra to compare these simulations to observed absorption spectra and find line-widths of ≈250 km s −1 , agreeing with the lower end of observations.

This work presents a parallel algorithm to produce high-quality shaded pictures directly from Constructive Solid Geometry (CSG) in early real time. The algorithm performs a pixel parallelization of the Ray Casting tecnique of CSG models. L'articolo propone un nuovo approccio al problema della parallelizzazione dell'algoritmo di Ray Casting di modelli CSG su architettura SIMD (Connection Machine) . Dopo una breve descrizione del problema affrontato viene presentato l'algoritmo implementato ed irisultati ottenuti. Keywords : Parallel Computing, Computer Graphics, Geometric Modeling, Solid Modeling, CSG Evaluation, RayTracing, Image Synthesis. 1. Introduction The techniques to visualize geometric models depend from the scheme of representation used to describe the model. The main problem is the high computational time. Da alcuni anni nella progettazione assistita dal calcolatore (CAD) e' cresciuto l'interesse per i sistemi in grado di manipolare sofisticati mod...

Density estimation techniques such as the photon map method rely on a particle transport simulation to reconstruct indirect illumination, which is proportional to the particle density. In the photon map framework, particles are usually located using nearest-neighbour methods due to their generality. However, these methods have an inherent tradeoff between local bias and noise in the reconstructed illumination, which depends on the density estimate bandwidth. This paper presents a bias compensating operator for nearest-neighbour density estimation which adapts the bandwidth according to the estimated bias in the reconstructed illumination.

A computational approach is presented, which uses the finite volume (FV) method in the Computational Fluid Dynamics (CFD) sol-ver ANSYS Fluent to conduct the ray tracing required to quantify the optical performance of a line concentration Concentrated Solar Power (CSP) receiver, as well as the conjugate heat transfer modelling required to estimate the thermal efficiency of such a receiver. A Linear Fresnel Collector (LFC) implementation is used to illustrate the approach. It is shown that the Discrete Ordinates method can provide an accurate solution to the Radiative Transfer Equation (RTE) if the shortcomings of its solution are resolved appropriately in the FV CFD solver. The shortcomings are due to false scattering and the so-called ray effect inherent in the FV solution. The approach is first evaluated for a 2-D test case involving oblique collimated radiation and then for a more complex 2-D LFC optical domain based on the FRESDEMO project. For the latter, results are compared w...

This technical report documents the development of the RADIANCE photon mapping extension and its integration into the official RADIANCE 5.0 distribution. A number of new techniques are now supported for a more efficient daylight simulation workflow, notably support for data driven material models via the bsdf modifier, and ray coefficients for climate based daylight modelling using the rcontrib tool. This document focuses primarily on the implementation details of the photon mapping software in support of this new functionality.