Shading Algorithm Research Articles

A novel mathematical control algorithm (HNU Shading) for different window shades based on HNU solar model

Window shading control helps maximize daylight use for creating comfortable indoor luminous environments and reduces over-illuminance and glare discomfort. This study proposes a novel mathematical algorithm (the HNU Shading algorithm) for calculating the distribution of direct sunlight indoors and adjusting window shades to avoid over-illuminance and glare indoors. The algorithm uses the sun position, window-ambient illuminance, window design parameters, and the controlled area (desktop and occupant’s head) as inputs to control different window shades (the vertical blind, horizontal blind, exterior awning, and interior shutter in this study), and the performance was verified via experiments and simulations. The results show that the HNU Shading algorithm has a high precision level of predicting the distribution area of direct sunlight with the error at 0.01–0.07 m. And it prevents the high illuminance from the desktop and keeps it lower than 3,000 lx under most of conditions with different window directions, shade types, seasons, and sunlight intensities. Meanwhile, with the HNU Shading algorithm, the Daylight Glare Probability (DGP) is lower than 0.4 during the period when intolerable glare happens. This study contributes to configuring practical and universal real-time window shading controls for different buildings with different window shade types, such as offices, classrooms, libraries, airports, and railway stations.

Pixel-level Terrain Processing of the Martian Surface from Moderate Resolution Images of Tianwen-1

The moderate-resolution camera (MoRIC) of the Tianwen-1 orbiter, China’s first Mars exploration mission, is a frame-imaging scheme color camera. However, generating a precise digital elevation model (DEM) from these images faces challenges due to the presence of featureless and repetitive regions on the Martian surface. Traditional photogrammetric methods often struggle to achieve pixel-level resolution in these areas. To address this, we employ a shape from shading (SFS) algorithm that leverages shading patterns to reconstruct fine-scale terrain details, optimizing photogrammetric initial DEM. This paper presents a novel global bisection search algorithm, based on the Pearson correlation coefficient to determine the smoothing parameter, a crucial element in the SFS process. Comparisons with higher-resolution data from the Mars Express high-resolution stereo camera and Mars Reconnaissance Orbiter CTX images validate our approach, highlighting the potential of SFS to significantly enhance the scientific value of Tianwen-1 MoRIC data by generating high-resolution, three-dimensional maps of Mars.

Estimation of ultrasonic flight time based on SHADE algorithm and extended kalman filtering

Abstract Traditional methods of using ultrasound to measure oxygen concentration have the issue of inaccuracy and susceptibility to noise interference when measuring the time of flight (TOF) of ultrasonic echo signals. A proposed algorithm for ultrasonic parameter estimation, utilizing an asymmetric Gaussian model, aims to enhance the precision and reliability of TOF estimation, aiming to reduce the influence of noise interference. The algorithm combines an improved Self-Adaptive Differential Evolution (SHADE) algorithm based on successful historical records with an Extended Kalman Filter (EKF). The improved SHADE algorithm controls the degree of mutation strategy greediness during the mutation operation based on the number of iterations, thereby enhancing the algorithm’s iteration speed. Then, the obtained solution is used as the initial value for the EKF to estimate the model parameters, thus addressing the issue of EKF’s dependency on accurate initial values to obtain precise outputs. Through simulation and experimental measurements of ultrasonic oxygen concentration, several commonly used parameter estimation algorithms are compared with the proposed SHADE-EKF algorithm. Results demonstrate that the SHADE-EKF algorithm exhibits superior performance in estimating the TOF of ultrasonic waves.

Single-Image-Based 3D Reconstruction of Endoscopic Images.

A wireless capsule endoscope (WCE) is a medical device designed for the examination of the human gastrointestinal (GI) tract. Three-dimensional models based on WCE images can assist in diagnostics by effectively detecting pathology. These 3D models provide gastroenterologists with improved visualization, particularly in areas of specific interest. However, the constraints of WCE, such as lack of controllability, and requiring expensive equipment for operation, which is often unavailable, pose significant challenges when it comes to conducting comprehensive experiments aimed at evaluating the quality of 3D reconstruction from WCE images. In this paper, we employ a single-image-based 3D reconstruction method on an artificial colon captured with an endoscope that behaves like WCE. The shape from shading (SFS) algorithm can reconstruct the 3D shape using a single image. Therefore, it has been employed to reconstruct the 3D shapes of the colon images. The camera of the endoscope has also been subjected to comprehensive geometric and radiometric calibration. Experiments are conducted on well-defined primitive objects to assess the method's robustness and accuracy. This evaluation involves comparing the reconstructed 3D shapes of primitives with ground truth data, quantified through measurements of root-mean-square error and maximum error. Afterward, the same methodology is applied to recover the geometry of the colon. The results demonstrate that our approach is capable of reconstructing the geometry of the colon captured with a camera with an unknown imaging pipeline and significant noise in the images. The same procedure is applied on WCE images for the purpose of 3D reconstruction. Preliminary results are subsequently generated to illustrate the applicability of our method for reconstructing 3D models from WCE images.

Wear depth estimation from single 2-D image based on shape from Shading and convolutional neural network hybrid model for in-situ wear assessment

Vision-based wear inspection is a prevalent technique in in-situ assessment, such as borescope inspection. Evaluating wear volume of the damage has relied on Shape From Shading (SFS) algorithms to reconstruct the 3-D topography from a single 2-D image. However, this approach faces limitations in accuracy due to data insufficiency and the impact of non-Lambertian reflections on a 2-D surface image. To address this issue, a depth estimation method is proposed, centered on an SFS-Convolutional Neural Network (CNN) hybrid model. First, in terms of the insufficient information of a 2-D image, a coarse-to-fine detection network has been developed to identify the damage region. Regarding the influence of the non-Lambert reflection of the worn surface, an SFS-CNN hybrid model is constructed incorporating an SFS-based guidance branch and a CNN branch based on a dual-attention mechanism. Specifically, the latter emphasizes the connection between the 2-D damage image and the depth information, disregarding non-Lambertian reflection, while the former extracts the initial depth information from the damage region for CNN learning. Consequently, the wear volume can be derived by accumulating the depth of the reconstructed 3-D worn region. To verify, several real worn surfaces have been used and examined using the proposed model and Laser Scanning Confocal Microscopy. Experimental results indicate that the proposed method can determine the depth of a worn surface from a single surface image, and the absolute relative error of the computed wear volume is less than 19 %, which satisfies the requirement of in-situ wear condition assessment.

Large-Scale Exact Epidemiological Modelling with Multi-Dimensional Constrained Optimization Approaches.

Multi-dimensional prediction models of the pandemic diseases should be constructed in a way to reflect their peculiar epidemiological characters. In this paper, a graph theory-based constrained multi-dimensional (CM) mathematical and meta-heuristic algorithms (MA) are formed to learn the unknown parameters of a large-scale epidemiological model. The specified parameter signs and the coupling parameters of the sub-models constitute the constraints of the optimization problem. In addition, magnitude constraints on the unknown parameters are imposed to proportionally weight the input-output data importance. To learn these parameters, a gradient-based CM recursive least square (CM-RLS) algorithm, and three search-based MAs; namely, the CM particle swarm optimization (CM-PSO), the CM success history-based adaptive differential evolution (CM-SHADE), and the CM-SHADEWO enriched with the whale optimization (WO) algorithms are constructed. The traditional SHADE algorithm was the winner of the 2018 IEEE congress on evolutionary computation (CEC) and its versions in this paper are modified to create more certain parameter search spaces. The results obtained under the equal conditions show that the mathematical optimization algorithm CM-RLS outperforms the MA algorithms, which is expected since it uses the available gradient information. However, the search-based CM-SHADEWO algorithm is able to capture the dominant character of the CM optimization solution and produce satisfactory estimates in the presence of the hard constraints, uncertainties and lack of gradient information.

DUET: A Novel Energy Yield Model With 3-D Shading for Bifacial Photovoltaic Systems

Bifacial photovoltaic (PV) performance models strive to accurately quantify rear-incident irradiance. While ray tracing models are optically rigorous, they require significant computational resources; faster view factor (VF) models are widely adopted but require user-defined loss factors to approximate rear shading and irradiance nonuniformity, introducing uncertainty in energy yield predictions. This article describes DUET—a bifacial PV performance model that calculates optical and electrical performance based on a physically representative array geometry. DUET’s novel shading algorithm pairs a 3-D VF model with deterministic ray-object intersections to capture 2-D shade-inclusive irradiance profiles while minimizing computational cost. Series and parallel combination of current–voltage curves capture irradiance nonuniformity throughout the module and array. This article provides validation against open-access system measurements from a test site in Roskilde, Denmark, and comparison to other software tested there [1]. DUET’s modeled bifacial energy yield agrees with measured data within −1.56% for fixed-tilt and −0.65% for horizontal single-axis tracked (HSAT) systems. Mean absolute error (MAE) in hourly bifacial power is 14.2–15.0 mW/Wp for fixed-tilt and 17.3–18.3 mW/Wp for HSAT, depending on the module temperature model applied. Comparing modeled and measured rear irradiance of two rear-facing pyranometers, DUET’s MAE values of 2.8 W/m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> for fixed-tilt and 3.7 W/m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> for HSAT are among the lowest errors reported for other software tested at this site. DUET provides computationally efficient bifacial performance modeling with geographic, temporal, and structural specificity to determine loss factors for use in other performance models or to be used directly in system design optimization.

Multirate Shading with Piecewise Interpolatory Approximation

AbstractEvaluating shading functions on geometry surfaces dominates the rendering computation. A high‐quality but time‐consuming estimate is usually achieved with a dense sampling rate for pixels or sub‐pixels. In this paper, we leverage sparsely sampled points on vertices of dynamically‐generated subdivision surfaces to approximate the ground‐truth shading signal by piecewise linear reconstruction. To control the introduced interpolation error at runtime, we analytically derive an L∞ error bound and compute the optimal subdivision surfaces based on a user‐specified error threshold. We apply our analysis on multiple shading functions including Lambertian, Blinn‐Phong, Microfacet BRDF and also extend it to handle textures, yielding easy‐to‐compute formulas. To validate our derivation, we design a forward multirate shading algorithm powered by hardware tessellator that moves shading computation at pixels to the vertices of subdivision triangles on the fly. We show our approach significantly reduces the sampling rates on various test cases, reaching a speedup ratio of 134% ~ 283% compared to dense per‐pixel shading in current graphics hardware.

ADBSat: Methodology of a novel panel method tool for aerodynamic analysis of satellites

ADBSat is a novel software that determines the aerodynamic properties of any body in free-molecular flow. Its main advantage is the fast approximation of the aerodynamics of spacecraft in the lower end of the low-Earth orbit altitude range. It is a novel implementation of a panel method, where the body is represented as a set of fundamental elements and the sum of their individual aerodynamic properties makes up the properties of the whole. ADBSat's approach treats the shape as a set of flat triangular plates. These are read from a CAD geometry file in the Wavefront format, which can be created with most common CAD programs. A choice of gas-surface interaction models is available to represent the physics of free-molecular flow under different conditions. Its modular design means that other models can be easily and quickly implemented. It also benefits from a new shading algorithm for fast determination of elemental flow exposure. An example case is presented to show the capability and functionality of the program. Program summaryProgram Title: ADBSatCPC Library link to program files:https://doi.org/10.17632/622n2yjg4w.1Licensing provisions: GPLv3Programming language: MATLABDeveloper's repository link:https://github.com/nhcrisp/ADBSatNature of problem: Quickly and accurately determining the aerodynamics of satellites in free-molecular flow.Solution method: A new implementation of the panel method has been devised. The satellite shape is passed to the program as a CAD model, comprised of a set of flat triangular plates. ADBSat then calculates the aerodynamic characteristics of each element using an appropriate mathematical model, and sums the contributions for the overall properties of the body. A novel shading algorithm identifies and removes the panels which do not contribute to the calculations due to being protected from the flow by other body features. ADBSat also has the capability to account for different materials within the shape.Additional comments including restrictions and unusual features: MATLAB's Aero-space Toolbox is required for the determination of environmental parameters, unless otherwise provided by the user. As the program takes as an input a completed model of the spacecraft, the user is responsible for all mesh quality checks. The methods employed therein are only valid for strict free-molecular flow, which the user must ensure. The accuracy of the method decreases for surfaces with high concavity or multiple particle impingement.

ADBSat: Verification and validation of a novel panel method for quick aerodynamic analysis of satellites

We present the validation of ADBSat, a novel implementation of the panel method including a fast pseudo-shading algorithm, that can quickly and accurately determine the forces and torques on satellites in free-molecular flow. Our main method of validation is comparing test cases between ADBSat, the current de facto standard of direct simulation Monte Carlo (DSMC), and published literature. ADBSat exhibits a significantly shorter runtime than DSMC and performs well, except where deep concavities are present in the satellite models. The shading algorithm also experiences problems when a large proportion of the satellite surface area is oriented parallel to the flow, but this can be mitigated by examining the body at small angles to this configuration (± 0.1°). We recommend that an error interval on ADBSat outputs of up to 3% is adopted. Therefore, ADBSat is a suitable tool for quickly determining the aerodynamic characteristics of a wide range of satellite geometries in different environmental conditions in VLEO. It can also be used in a complementary manner to identify cases that warrant further investigation using other numerical-based methods.

Optimization Algorithm Design of Laser Marking Contour Extraction and Graphics Hatching Based on Image Processing Technology

On the premise of solving the problem in a specific situation, this paper aims at the laser marking machine for the design and optimization of the outline extraction of the two-dimensional composite curve figure and the figure hatching scheme. The scanning line algorithm based on computer graphics and the polygon hatching are based on the algorithm theory. Based on the foundation, an improved polygon scan line algorithm model is established, and the contour extraction and graphic shadows of two-dimensional polygons are realized by MATLAB programming. The simulation results show that our algorithm model can meet our requirements well, and at the same time has a certain improvement effect. At the same time, compared with traditional two-dimensional polygon scanning and hatching algorithms, our algorithm model has strong analysis and processing capabilities and strong applicability. Compared with traditional two-dimensional polygon scanning and shading algorithms, model analysis can still run stably in a high refresh rate environment. We hope to further optimize the algorithm in the later stage, so that it can be better used in related engineering fields.

Tracker Terrain Loss Part Two

Trackers on variable terrain can incur electric mismatch losses from row-to-row shading even with backtracking. Tracker terrain loss is the difference between the performance of trackers on horizontal ground and that on variable terrain. SolarFarmer was used to study tracker terrain loss by simulating the Hopewell Friends Solar power plant, which has an average 4% southwest slope. The results yielded a tracker terrain loss of −2% with standard backtracking and slope-aware backtracking completely recovered the 2% loss. By subdividing the site from one to three layouts, the tracker terrain loss decreased 0.5%. The 1-h versus 5-min input data did not significantly affect the tracker terrain loss. This study is a continuation of a previous study that prompted improvements in SolarFarmer's 3-D tracker shading algorithm. The results of this study demonstrate that SolarFarmer can now be used to calculate tracker terrain loss. A comparison of the SolarFarmer results with a separate uneven terrain model developed by DNV using PVsyst produced similar results.

152 Evaluation of the SkinCam, a Connected Portable Camera Device, for the Analysis of Skin Microrelief

Silicone replicas and non-contact methods are effective in analysing the micrometric scale of the plateaus and furrows that forms the skin microrelief. Yet, a major drawback is the obligation to capture data in research facilities. Therefore, the capacities of a connected portable camera device, the SkinCam, was evaluated to analyse the skin microrelief in real-time and while subjects were living their regular daily life routine. The effect of moisturisers on microrelief was also analysed. From RGB data, 3D depth maps were constructed using shape from shading algorithms.

Photometric stereo-based high-speed inline battery electrode inspection

AbstractBattery technology is a key component in current electric vehicle applications and an important building block for upcoming smart grid technologies. The performance of batteries depends largely on quality control during their production process. Defects introduced in the production of electrodes can lead to degraded performance and, more importantly, to short circuits in final cells, which is highly safety-critical. In this paper, we propose an inspection system architecture that can detect defects, such as missing coating, agglomerates, and pinholes on coated electrodes. Our system is able to acquire valuable production quality control metrics, like surface roughness. By employing photometric stereo techniques (PS), a shape from shading algorithm, our system surmounts difficulties that arise while optically inspecting the black to dark gray battery coating materials. We present in detail the acquisition concept of the proposed system architecture, and analyze its acquisition-, as well as, its surface reconstruction performance in experiments. We carry these out utilizing two different implementations that can operate at a production speed of up to 2000 mm/s at a resolution of 50 µm per pixel. In this work we aim to provide a system architecture that can provide a reliable contribution to ensuring optimal performance of produced battery cells.

Investigation of Improved Cooperative Coevolution for Large-Scale Global Optimization Problems

Modern real-valued optimization problems are complex and high-dimensional, and they are known as “large-scale global optimization (LSGO)” problems. Classic evolutionary algorithms (EAs) perform poorly on this class of problems because of the curse of dimensionality. Cooperative Coevolution (CC) is a high-performed framework for performing the decomposition of large-scale problems into smaller and easier subproblems by grouping objective variables. The efficiency of CC strongly depends on the size of groups and the grouping approach. In this study, an improved CC (iCC) approach for solving LSGO problems has been proposed and investigated. iCC changes the number of variables in subcomponents dynamically during the optimization process. The SHADE algorithm is used as a subcomponent optimizer. We have investigated the performance of iCC-SHADE and CC-SHADE on fifteen problems from the LSGO CEC’13 benchmark set provided by the IEEE Congress of Evolutionary Computation. The results of numerical experiments have shown that iCC-SHADE outperforms, on average, CC-SHADE with a fixed number of subcomponents. Also, we have compared iCC-SHADE with some state-of-the-art LSGO metaheuristics. The experimental results have shown that the proposed algorithm is competitive with other efficient metaheuristics.

Cartographic Relief Shading with Neural Networks.

Shaded relief is an effective method for visualising terrain on topographic maps, especially when the direction of illumination is adapted locally to emphasise individual terrain features. However, digital shading algorithms are unable to fully match the expressiveness of hand-crafted masterpieces, which are created through a laborious process by highly specialised cartographers. We replicate hand-drawn relief shading using U-Net neural networks. The deep neural networks are trained with manual shaded relief images of the Swiss topographic map series and terrain models of the same area. The networks generate shaded relief that closely resemble hand-drawn shaded relief art. The networks learn essential design principles from manual relief shading such as removing unnecessary terrain details, locally adjusting the illumination direction to accentuate individual terrain features, and varying brightness to emphasise larger landforms. Neural network shadings are generated from digital elevation models in a few seconds, and a study with 18 relief shading experts found that they are of high quality.

High Resolution Digital Terrain Models of Mercury

We refined our Shape from Shading (SfS) algorithm, which has previously been used to create digital terrain models (DTMs) of the Lunar and Martian surfaces, to generate high-resolution DTMs of Mercury from MESSENGER imagery. To adapt the reconstruction procedure to the specific conditions of Mercury and the available imagery, we introduced two methodic innovations. First, we extended the SfS algorithm to enable the 3D-reconstruction from image mosaics. Because most mosaic tiles were acquired at different times and under various illumination conditions, the brightness of adjacent tiles may vary. Brightness variations that are not fully captured by the reflectance model may yield discontinuities at tile borders. We found that the relaxation of the constraint for a continuous albedo map improves the topographic results of an extensive region removing discontinuities at tile borders. The second innovation enables the generation of accurate DTMs from images with substantial albedo variations, such as hollows. We employed an iterative procedure that initializes the SfS algorithm with the albedo map that was obtained by the previous iteration step. This approach converges and yields a reasonable albedo map and topography. With these approaches, we generated DTMs of several science targets such as the Rachmaninoff basin, Praxiteles crater, fault lines, and several hollows. To evaluate the results, we compared our DTMs with stereo DTMs and laser altimeter data. In contrast to coarse laser altimetry tracks and stereo algorithms, which tend to be affected by interpolation artifacts, SfS can generate DTMs almost at image resolution. The root mean squared errors (RMSE) at our target sites are below the size of the horizontal image resolution. For some targets, we could achieve an effective resolution of less than 10 m/pixel, which is the best resolution of Mercury to date. We critically discuss the limitations of the evaluation methodology.

SEBEpv – New digital surface model based method for estimating the ground reflected irradiance in an urban environment

Knowing the solar radiation fluxes inside an urban canyon is of interest for different purposes: e.g. urban climatology and studies of human thermal comfort and gaining relevance for future renewable energy generation in an urban environment using photovoltaic systems. For the latter, mainly rooftops are of interest, but studies started to extend towards the solar resources on building facades. However, the reflected solar radiation from the ground is either neglected or estimated using simplifications that lead to overestimation.SEBEpv (Solar Energy on Building Envelope – photovoltaic) is a new tool attempting to provide better estimates for the radiation reflected from the ground onto facades. It is primarily intended for the urban environment where the ground-view is very limited. SEBEpv delivers 3D results based on digital surface models of the environment. Furthermore, an optional PV model was added in order to address the simplified of estimation of reflected radiation when modelling photovoltaic (PV) yields.SEBEpv delivers quite good estimates for the solar radiation compared to the measurements. The simulated irradiance shows an RMSE of 28.7 W/m2 compared to the measured irradiance and has a bias close to zero. This is about half the RMSE shown by the predecessor tool SEBE. The measured total irradiation over two years shows a bias of about 7%, which is likely to be a result of the limited angular resolution of the shading algorithm. Overall, SEBEpv seems to be a promising tool, accounting for reflected radiation in urban environments.

Error assessment of grid‐based terrain shading algorithms for solar radiation modeling over complex terrain

AbstractIn mountainous regions, solar radiation exhibits a strong spatial heterogeneity due to terrain shading effects. Terrain shading algorithms based on digital elevation models can be categorized into two types: area‐based and point‐specific. In this article, we evaluated two shading algorithms using designed mathematic surfaces. Theoretical shading effects over four Gauss synthetic surfaces were calculated and used to evaluate the terrain shading algorithms. We evaluated the area‐based terrain shading algorithm, Hillshade tool of ArcGIS, and the point‐specific shading algorithm from Solar Analyst (SA) in ArcGIS. Both algorithms showed shading overestimation, and Hillshade showed more accuracy with a mean absolute error (MAE) of 1.20%, as compared to the MAE of 1.66% of SA. The MAE of Hillshade increases exponentially as the spatial extent of the study area increases because the solar position for all locations on the surface is the same in Hillshade. Consequently, we suggest that the surface should be divided into more tiles in Hillshade when the discrepancy in the latitude of the whole surface is greater than 4°. Skyshed, which represents the horizon angle distribution in SA, is error‐prone over more complex terrain because horizon angle interpolation is problematic for such areas. We also propose a new terrain shading algorithm, with solar positions calculated using local latitude for each cell and the horizon angle calculated for every specific time interval, but without projections. The new model performs better than Hillshade and SA with an MAE of 0.55%.

Simulation of shading and algal growth in experimental raceways

Many algae research groups use elevated experimental raceways to characterize algal biomass productivity. Side walls and a relatively large paddlewheel shade the culture and lower productivity, particularly in winter and with low culture depth. This paper presents a four-step method to calculate shading for a given raceway shape: (1) develop a computational mesh of the inner surface geometry of the raceway; (2) offset the mesh horizontally in the x and y directions on the water surface as a function of wall height, solar zenith angle, and solar azimuth angle; (3) calculate the shaded area for each projected mesh with the shoelace algorithm; (4) use regression to develop a response surface for shaded area as a function of horizontal x and y offset. For each time step, the shaded area is calculated with the regression equation based on the x and y offset at that time step. The shading model was added to the Huesemann Algae Biomass Growth (HABG) model. In the model, productivity was sensitive to the assumed light distribution below the water surface. Shading and light distribution models were evaluated with biomass concentrations from three Regional Algal Feedstock Testbed (RAFT) experiments with three different species of algae. Averaging light in each layer resulted in higher calculated growth rate than calculating growth separately in shaded and unshaded areas. The Local Photon Flux Density Variable Light (LPFD_V) shading algorithm reduced the HABG estimate of productivity and improved the agreement with observed productivities. The LPFD_V RMSD values ranged between 0.01 and 0.07 g L−1 and the bias factors ranged between 0.9 and 1.1. Shaded area was sensitive to raceway orientation, water depth, and time of year. A north-south raceway orientation had less average shading in winter but more average shading in summer than an east-west orientation.