Fast Ray Tracing Research Articles

Spectral reconstruction for radiation hydrodynamic simulations of galaxy evolution

Radiation from stars and active galactic nuclei (AGN) plays an important role in galaxy formation and evolution, and profoundly transforms the intergalactic, circumgalactic, and interstellar medium (IGM, CGM, and ISM). On-the-fly radiative transfer (RT) has started being incorporated in cosmological simulations, but the complex evolving radiation spectra are often crudely approximated with a small number of broad bands with piece-wise constant intensity and a fixed photo-ionisation cross-section. Such a treatment is unable to capture the changes to the spectrum as light is absorbed while it propagates through a medium with non-zero opacity. This can lead to large errors in photo-ionisation and heating rates. In this work we present a novel approach of discretising the radiation field at discrete photon energies, at the edges of the typically used photo-ionising bands, in order to capture the power-law slope of the radiation field. In combination with power-law approximations for the photo-ionisation cross-sections, this model allows us to self-consistently combine radiation from sources with different spectra and accurately follow the ionisation states of primordial and metal species through time. The method is implemented in GASOLINE2 in connection with TREVR2, a fast reverse ray tracing algorithm with 𝒪(Nactive log2 N) scaling. We compare our new piece-wise power-law reconstruction to the piece-wise constant method in calculating the primordial chemistry photo-ionisation and heating rates under an evolving UV background (UVB) and stellar spectrum, and find that our method reduces errors significantly, by up to two orders of magnitude in the case of HeII ionisation. We apply our new spectral reconstruction method in RT post-processing of a cosmological zoom-in simulation, MUGS2 g1536, including radiation from stars and a live UVB, and find a significant increase in total neutral hydrogen (HI) mass in the ISM and the CGM due to shielding of the UVB and a low escape fraction of the stellar radiation. This demonstrates the importance of RT and an accurate spectral approximation in simulating the CGM-galaxy ecosystem.

Faster Ray Tracing through Hierarchy Cut Code

AbstractWe propose a novel ray reordering technique designed to accelerate the ray tracing process by encoding and sorting rays prior to traversal. Our method, called “hierarchy cut code”, involves encoding rays based on the cuts of the hierarchical acceleration structure, rather than relying solely on spatial coordinates. This approach allows for a more effective adaptation to the acceleration structure, resulting in a more reliable and efficient encoding outcome. Furthermore, our research identifies “bounding drift” as a major obstacle in achieving better acceleration effects using longer sorting keys in existing reordering methods. Fortunately, our hierarchy cut code successfully overcomes this issue, providing improved performance in ray tracing. Experimental results demonstrate the effectiveness of our approach, showing up to a 1.81 times faster secondary ray tracing compared to existing methods. These promising results highlight the potential for further enhancement in the acceleration effect of reordering techniques, warranting further exploration and research in this exciting field.

FVDB : A Deep-Learning Framework for Sparse, Large Scale, and High Performance Spatial Intelligence

We present f VDB, a novel GPU-optimized framework for deep learning on large-scale 3D data. f VDB provides a complete set of differentiable primitives to build deep learning architectures for common tasks in 3D learning such as convolution, pooling, attention, ray-tracing, meshing, etc. f VDB simultaneously provides a much larger feature set (primitives and operators) than established frameworks with no loss in efficiency: our operators match or exceed the performance of other frameworks with narrower scope. Furthermore, f VDB can process datasets with much larger footprint and spatial resolution than prior works, while providing a competitive memory footprint on small inputs. To achieve this combination of versatility and performance, f VDB relies on a single novel VDB index grid acceleration structure paired with several key innovations including GPU accelerated sparse grid construction, convolution using tensorcores, fast ray tracing kernels using a Hierarchical Digital Differential Analyzer algorithm (HDDA), and jagged tensors. Our framework is fully integrated with PyTorch enabling interoperability with existing pipelines, and we demonstrate its effectiveness on a number of representative tasks such as large-scale point-cloud segmentation, high resolution 3D generative modeling, unbounded scale Neural Radiance Fields, and large-scale point cloud reconstruction.

Study and validation of a fast ray tracing method to determine density flux for symmetric solar optical systems

In this research paper, a computational program called MCMRDF-3D, is developed and validated by comparison with a reference software. MCMRDF-3D is formulated on Multi-Ray Monte Carlo Method for the determination of the distribution of solar irradiation along the receiver of any solar- concentrating system that withstand translational or rotational symmetries. This code incorporate an advantageous approach that consist in estimating the overall distribution of irradiation of a large scale solar concentrating systems on the basis of a consistent sample, then saving computation time, processor capacity and storage memory. The paper presents the new approach and applied it to determine the distribution of irradiation provided by three concentrators. We compare the processing time, the irradiation map rendering, and the size of numeric data, to those provided by a Reference software. The obtained irradiation distribution and power harvesting quantities over the receiver matches very well. We conclude that MCMRDF-3D proves to easy, fast, accurate and reliable approach for the simulation of solar concentrator system. Among other implications, this work opens a path for saving time when studying numerous symmetrical imaged and non-imaged optical systems. For future work, this time saving and flexible program will be of a significant help to envision optical errors from real behavior of optical surface in concentrating systems.

Intelligent wireless resource management in industrial camera systems: Reinforcement Learning-based AI-extension for efficient network utilization

In this paper, we present an innovative method for replacing wired communication within an operational agile production cell with wireless communication, using a minimal number of access points. Our approach utilizes Reinforcement Learning (RL) to optimize the layout and minimize the required number of access points. We introduce an Artificial Intelligence (AI) agent that facilitates cooperative interaction between cameras and access points, optimizing camera stream utilization and radio coverage. This solution benefits from the recent standardization of The fifth generation of mobile communications (5G) Network Resource Management (NRM) features of the User Equipment (UE) attached to the cameras. To accommodate the dynamic nature of the production cell, our optimization algorithms run during cell operation, necessitating extended training times.Our contributions extend beyond the state-of-the-art by offering a Digital Twin (DT) environment equipped with physics and radio propagation capabilities, fast raytracing for radio propagation modeling, curriculum-learning-based reinforcement learning, and a Physical Twin (PT) of the radio-connected camera with self-adjusting scene setup capabilities. This comprehensive proposal combines the efficiency of 5G radio utilization with precise modeling and high-resolution simulations, while also significantly improving training speed.In the Agile Robotics for Industrial Automation Competition (ARIAC) 2020 environment, our methods showed compelling results, with curriculum learning achieving a remarkable 3x speed-up compared to non-curriculum approaches. We also demonstrated that high Quality of Service (QoS) demands can be reduced to just 2% of total time while maintaining consistent productivity Key Performance Indicators (KPIs). Furthermore, we explored the integration of these methods into Internet of Things (IoT) devices with limited performance capabilities. In conclusion, our approach offers significant benefits and savings for IoT devices, networks, edge clouds, and industry players.

Large‐scale spatiotemporal calculation of photovoltaic capacity factors using ray tracing: A case study in urban environments

AbstractPhotovoltaics (PVs) on building facades, either building‐integrated or building‐attached, offer a large energy yield potential especially in densely populated urban areas. Targeting this potential requires the availability of planning tools such as insolation forecasts. However, calculating the PV potential of facade surfaces in an urban environment is challenging. Complex time‐dependent shadowing and light reflections must be considered. In this contribution, we present fast ray tracing calculations for insolation forecasts in large urban environments using clustering of Sun positions into typical days. We use our approach to determine time resolved PV capacity factors for rooftops and facades in a wide variety of environments, which is particularly useful for energy system analyses. The advantage of our approach is that the determined capacity factors for one geographic location can be easily extended to larger geographic regions. In this contribution, we perform calculations in three exemplary environments and extend the results globally. Especially for facade surfaces, we find that there is a pronounced intra‐day and also seasonal distribution of PV potentials that strongly depends on the degree of latitude. The consideration of light reflections in our ray tracing approach causes an increase in calculated full load hours for facade surfaces between 10% and 25% for most geographical locations.

An SAR Imaging and Detection Model of Multiple Maritime Targets Based on the Electromagnetic Approach and the Modified CBAM-YOLOv7 Neural Network

This paper proposes an Synthetic Aperture Radar (SAR) imaging and detection model of multiple targets at the maritime scene. The sea surface sample is generated according to the composite rough surface theory. The SAR imaging model is constructed based on a hybrid EM calculation approach with the fast ray tracing strategy and the modified facet Small Slope Approximation (SSA) solution. Numerical simulations calculate the EM scattering and the SAR imaging of the multiple cone targets above the sea surface, with the scattering mechanisms analyzed and discussed. The SAR imaging datasets are then set up by the SAR image simulations. A modified YOLOv7 neural network with the Spatial Pyramid Pooling Fast Connected Spatial Pyramid Convolution (SPPFCSPC) module, Convolutional Block Attention Module (CBAM), modified Feature Pyramid Network (FPN) structure and extra detection head is developed. In the training process on our constructed SAR datasets, the precision rate, recall rate, mAP@0.5 and mAP@0.5:0.95 are 97.46%, 90.08%, 92.91% and 91.98%, respectively, after 300 rounds of training. The detection results show that the modified YOLOv7 has a good performance in selecting the targets out of the complex sea surface and multipath interference background.

헤드 마운티드 디스플레이를 위한 시간 제약 렌더링을 이용한 적응적 포비티드 광선 추적법

Ray tracing-based rendering creates by far more realistic images than the traditional rasterization-based rendering. However, it is still burdensome when implemented for a Head-Mounted Display (HMD) system that demands a wide field of view and a high display refresh rate. Furthermore, for presenting high-quality images on the HMD screen, a sufficient number of ray sampling should be carried out per pixel to alleviate visually annoying spatial and temporal aliases. In this paper, we extend the recent selective foveated ray tracing technique by Kim et al. [<xref ref-type="bibr" rid="B1">1</xref>], and propose an improved real-time rendering technique that realizes the rendering effect of the classic Whitted-style ray tracing on the HMD system. In particular, by combining the ray tracing hardware-based acceleration technique and time-constrained rendering scheme, we show that fast HMD ray tracing is possible that is well suited to human visual systems.

A fast piecewise 3D ray tracing algorithm for determining slant total delays

A fast piecewise 3D ray tracing algorithm for determining slant total delays

End-to-end learned single lens design using fast differentiable ray tracing.

In traditional imaging system design, the optical lens is often optimized toward the artificial optimization target like modulation transfer function and field-of-view (FoV). This usually leads to complex stacks of lenses. In order to reduce the complexity, we propose an end-to-end single lens imaging system design method. First, the imaging and processing model is established, whose input end is the ground truth image, and the output end is the restored image by Res-Unet. Then, with the optimization target of minimizing the difference between the restored image and the ground truth image, the parameters of the lens surface and the parameters of the restoration algorithm are optimized simultaneously by deep learning. In order to realize the end-to-end design, the imaging model is required to be differentiable to the lens parameters, so a fast differentiable ray tracing model is proposed. A single lens imaging system with high-quality large FoV (47°) has been designed by the end-to-end method. This method will have a wide application prospects in the design of light and small optoelectronic imaging systems.

Dominant path determining method for millimeter wave propagation in indoor scenarios based on ant colony algorithm

A fast ray tracing method based on ant colony algorithm is proposed to analyze the indoor propagation characteristics of millimeter-wave more efficiently. This method uses ant colony distribution calculation and heuristic search principle to find the dominant ray path of radio wave propagation, which replaces the total ray path analysis to reduce the algorithm complexity and improve execution efficiency. Compared with the measured data results, the result of the simulation analysis of three frequency channel characteristics of 28 GHz, 32 GHz and 38 GHz in typical indoor scene shows better consistency, and the prediction error is less than 0.8 dB. The computational efficiency is improved by 378.9% compared with the traditional ray tracing method. The above-mentioned results show that the proposed method can effectively reduce the computational complexity under the premise of ensuring the prediction accuracy, and has the value of engineering application.

A Fast Ray-tracing Method for Locating Mining-Induced Seismicity by Considering Underground Voids

The accurate localization of mining-induced seismicity is crucial to underground mines. However, the constant velocity model is used by traditional location methods without considering the great difference in wave velocity between rock mass and underground voids. In this paper, to improve the microseismicity location accuracy in mines, we present a fast ray-tracing method to calculate the ray path and travel time from source to receiver considering underground voids. First, we divide the microseismic monitoring area into two categories of mediums—voids and non-voids—using a flexible triangular patch to model the surface model of voids, which can accurately describe any complicated three-dimensional (3D) shape. Second, the nodes are divided into two categories. The first category of the nodes is the vertex of the model, and the second category of the nodes is arranged at a certain step length on each edge of the 3D surface model to improve the accuracy of ray tracing. Finally, the set of adjacent nodes of each node is calculated, and then we obtain the shortest travel time from the source to the receiver based on the Dijkstra algorithm. The performance of the proposed method is tested by numerical simulation. Results show that the proposed method is faster and more accurate than the traditional ray-tracing methods. Besides, the proposed ray-tracing method is applied to the microseismic source localization in the Huangtupo Copper and Zinc Mine. The location accuracy is significantly improved compared with the traditional method using the constant velocity model and the FMM-based location method.

58 Monte Carlo modelling of photon propagation in a human head model containing an enhanced-absorbing target

Introduction. Modelling the light propagation inside brain tissue structures is still a challenging task which requires the use of complex computational schemes often based on Monte Carlo method [ 1 Vaudelle F. and L’Huillier J.P. Time-resolved optical fluorescence spectroscopy of heterogeneous turbid media with special emphasis on brain tissue structures including diseased regions: a sensitivity analysis. Opt Comm. 304 161–168 (2013). Google Scholar , 2 Mansouri C, L’Huillier JP, Kashou NH, Humeau A. Depth sensitivity analysis of functional near-infrared spectroscopy measurement using three-dimensional Monte Carlo modelling based magnetic resonance imaging. Lasers Med Sci. 25, 431-438 (2010). Google Scholar , 3 Fang Q. Mesh-based Monte Carlo method using fast ray tracing in Plücker coordinates. Biomed Opt Exp. 1 165–175 (2010). Google Scholar ]. Because of strong tissue-scattering process (NIR infrared range: 600–900 nm), deep probed structures receive much less light amount than the superficial tissues. This has the effect to impede optical measurements and efficient planning treatments. In this paper, we take an interest in noninvasive tissue arrangements for which a NIR light source strikes a human head model, and thus investigate how photons penetrate and interact with an enhanced-absorbing target located close to the CSF layer. The study especially aims at displaying the effects of tissue structure, optical properties, location and size of the inclusion, dye concentration and light source parameters on optical diagnostic and therapeutic treatment.

Numerical study of traveling ionosphere disturbances with vertical incidence data

High frequency ionosphere vertical sounding, as an important and representative application for detecting the ionosphere and studying the characteristics of radio propagation, can be utilized to monitor the ionosphere continuously variation and to acquire the ionosphere asymmetrical features of diverse scale above the ionosphere vertical sounding stations. This is a first article on real time application of numerical methods to obtain the parameters of traveling ionosphere disturbances (TIDs) using vertical incident ionograms. In this paper, the distribution of ionosphere electron density with TIDs is constructed using a background ionosphere model superimposed a perturbation theory model. The background ionosphere electron density is modelled by the inversion of vertical incident ionograms which are observed before the appearance of the disturbance. Based on the fourth order Adams-Bashforth-Moulton (the so-called ABM) predictor corrector method, instead of Runge-Kutta method, the fast digital ray tracing method is established. According to process of the disturbed trace simulation and parameters inversion, the characteristic parameters of ionosphere disturbance at different detection time can be obtained in real time. The numerical analysis of TIDs is then captured completely.

Bistatic Landmine and IED Detection Combining Vehicle and Drone Mounted GPR Sensors

This work proposes a novel Ground Penetrating Radar (GPR) system to detect landmines and Improvised Explosive Devices (IEDs). The system, which was numerically evaluated, is composed of a transmitter placed on a vehicle and looking forward and a receiver mounted on a drone and looking downwards. This combination offers both a good penetration and a high resolution, enabling the detection of non-metallic targets and mitigating the clutter at the air–soil interface. First, a fast ray tracing simulator was developed to find proper configurations of the system. Then, these configurations were validated using a full wave simulator, considering a flat and a rough surface. All simulations were post-processed using a fast and accurate Synthetic Aperture Radar (SAR) algorithm that takes into account the constitutive parameters of the soil. The SAR images for all configurations were compared, concluding that the proposed contribution greatly improves the target detection and the surface clutter reduction over conventional forward-looking GPR systems.

Simultaneous respiratory motion correction and image reconstruction in 4D-multi pinhole small animal SPECT.

Respiratory motion in the chest region during single photon emission computed tomography (SPECT) is a major degrading factor that reduces the accuracy of image quantification. This effect is more notable when the tumor is very small, or the spatial resolution of the imaging system is less than the respiratory motion amplitude. Small animals imaging systems with sub-millimeter spatial resolution need more attention to the respiratory motion for quantitative studies. We developed a motion-embedded four-dimensional (4D)-multi pinhole SPECT (MPS) reconstruction algorithm for respiratory motion correction. This algorithm makes full use of projection statistics for reconstruction of every individual frame. The ROBY phantom with small tumors in liver was generated in eight different phases during one respiratory cycle. The MPS projections were modeled using a fast ray tracing method simulating an MPS acquisition. Individual frames were reconstructed and used for motion estimation. The Demons non-rigid registration algorithm was used to calculate deformation vector fields (DVFs) for simultaneous motion correction and image reconstruction. A motion-embedded 4D-MPS method was used to reconstruct images using all the projections and corresponding DVFs, simultaneously. The 4D-MPS reconstructed images were compared to the low-count single frame (LCSF) reconstructed image, the three-dimensional (3D)-MPS images reconstructed using individual frames, and post reconstruction registration (PRR) that aligns all individual phases to a reference frame using Demons-derived DVFs. The tumor volume relative error (TVE), tumor contrast relative error (TCE), and dice index (DI) for 2, 3, and 4mm liver were calculated and compared for different reconstruction methods. For the 4D-MPS reconstruction method, TVE was reduced and DI was higher compared to PRR, 3D-MPS, and LCSF. The extent of the improvement was higher for the small tumor size (i.e. 2mm). For the biggest tumor in contrast 3 (i.e. 4mm) TVE for 4D-MPS, PRR, 3D-MPS and, LCSF were 1.33%, 8%, 8%, and 14.67%, respectively. The results suggest that motion-embedded 4D-MPS method is an effective and practical way for respiratory motion correction. It reconstructs high quality gated frames while using all projection data to reconstruct each frame.

Neutrino Vertex Reconstruction in South Pole Ice

Reconstruction of potential ultra-high-energy (UHE) neutrino events at the Askaryan Radio Array (ARA) is complicated by the variable index of refraction of South Pole ice, leading to curved radio signal paths from the interaction vertex. Using a spline table framework for fast raytracing approximation, we perform a GPU-accelerated interferometric reconstruction of the event vertex. We also demonstrate how use of both direct and reflected/refracted radio signals can allow reconstruction of the distance to the interaction vertex, an important step towards neutrino energy reconstruction.

Ray Tracing Dynamic Scenes Using Multiple Kd-trees

With faster hardware and algorithmic improvements, real-time ray tracing is finally within reach. A variety of different data structures have been developed for ray tracing over the past decades. These spatial data structures crucial for fast ray tracing must be rebuilt or updated as the scene changes, and this can become a bottle-neck for the speed of ray tracing. In this paper, a novel algorithm is proposed to improve the rendering speed for static and moving objects by build kd-trees respectively, i.e., we construct multiple kd-trees. This building method allows for ray tracing animations without rebuilding the spatial index structures for the whole scene, just for dynamic objects. We implement the proposed algorithm for ray tracing dynamic scene on CPU+GPU platform, resulting in frame rates of 3~5 fps for 1024*1024 images, which improves rendering speed of dynamic scenes significantly.

Quantitative evaluation of functional Near Infrared Spectroscopy measurements with different source-detector separations using Monte Carlo simulation

Quantitative evaluation of functional Near Infrared Spectroscopy measurements with different source-detector separations using Monte Carlo simulation

The Fast Ray Tracing in Calculating the Geometrical Optics Reflected Field

We consider the problem of the computer-aided construction of geometrical optics electromagnetic wave propagation paths (ray tracing). We indicate the disadvantages of widely applied Shooting and Bouncing Rays method. We also provide the examples of its software implementation. As opposed to the employed approaches, the method and the algorithm synthesized on its basis are introduced for the reflected ray tracing where the search process is implemented faster and there are no disadvantages inherent in their common counterparts.