Shading Model Research Articles

Terrain representation using orientation

ABSTRACT A terrain data model using orientation rather than elevation permits more efficient analysis and stores its data in a multi-band raster. Representation techniques from the computer graphics industry are readily adopted with this data model. A common data model for terrain surfaces–the raster digital elevation model (DEM)–carries with it limitations by emphasizing height. Derived products such as relief shading require additional processing to determine orientation, even though they are used more frequently than those relying on elevation (e.g. hypsometric tinting). We show some of the benefits of encoding and analyzing terrain based on surface orientation, an approach that uses normal vectors stored as multi-band raster, the data storage convention in the computer graphics industry. A change in the data model and the conceptualization of the surface’s defining characteristics allows relief shading methods to run faster than conventional tools. Processing efficiencies are especially useful for more advanced shading models that may employ hundreds of relief shading calculations. In addition, an orientation-focused approach to terrain permits cartographic techniques to parallel common computer graphics methods. This project explores one such method, normal-mapping, an effect that adds texture to conventional relief shading by perturbing surface normal vectors.

High-precision numerical calculation method of solar radiation pressure force for wrinkled solar sails

Due to small magnitude of solar radiation pressure (SRP), the area-mass ratio of the solar sail should be large enough to obtain adequate thrust acceleration. Therefore, the membrane structure is usually adopted for solar sails. However, the membrane barely has out-of-plane stiffness; thus, it is necessary to apply in-plane tension on the membrane for maintaining the plane, which may result in wrinkles. The wrinkle will influence SRP force of solar sails. On the one hand, wrinkled regions of the sail are no longer flat, so the angle between the normal vector of the surface in wrinkled regions and the direction of sunlight differ from a flat sail. On the other hand, wrinkles may cause shadow when the solar sail is almost parallel to sunlight and the shadow region cannot generate SRP force. In this paper, the nonlinear buckling theory is used to propose a numerical calculation method to solve the problem of wrinkling analysis of solar sails with complex boundary. Then, a high-precision method for calculating SRP force of wrinkled solar sails is proposed, consisting of two parts: the infinitesimal element SRP force model and the wrinkle shading model. Numerical simulation result verifies the effectiveness of the wrinkling analysis method and the SRP force calculation method. Furthermore, according to calculation result, wrinkles have a certain influence on the SRP force of the solar sail, which will become significant when the solar sail gets parallel to sunlight.

Fully Analytic Shading Model with Specular Reflections for Polygon-Based Hologram

Fully Analytic Shading Model with Specular Reflections for Polygon-Based Hologram

Perceptual model for adaptive local shading and refresh rate

When the rendering budget is limited by power or time, it is necessary to find the combination of rendering parameters, such as resolution and refresh rate, that could deliver the best quality. Variable-rate shading (VRS), introduced in the last generations of GPUs, enables fine control of the rendering quality, in which each 16×16 image tile can be rendered with a different ratio of shader executions. We take advantage of this capability and propose a new method for adaptive control of local shading and refresh rate. The method analyzes texture content, on-screen velocities, luminance, and effective resolution and suggests the refresh rate and a VRS state map that maximizes the quality of animated content under a limited budget. The method is based on the new content-adaptive metric of judder, aliasing, and blur, which is derived from the psychophysical models of contrast sensitivity. To calibrate and validate the metric, we gather data from literature and also collect new measurements of motion quality under variable shading rates, different velocities of motion, texture content, and display capabilities, such as refresh rate, persistence, and angular resolution. The proposed metric and adaptive shading method is implemented as a game engine plugin. Our experimental validation shows a substantial increase in preference of our method over rendering with a fixed resolution and refresh rate, and an existing motion-adaptive technique.

Parametric study of venetian blinds for energy performance evaluation and classification in residential buildings

Venetian blinds are widely used to improve the performance of window systems, while their energy-saving potentials vary with different materials. This paper aims to undertake a standardized evaluation of the annual energy-saving potential of venetian blinds in residential buildings, and identify the most influential parameters for design optimization. To achieve this goal, nine parameters were chosen to establish venetian blinds models in WINDOW. Then, 9072 shading models were coupled with building models for annual energy consumption simulation in EnergyPlus, where the shading schedule was derived from questionnaires. Further, an experiment was conducted to verify the reliability of the joint simulation between WINDOW and EnergyPlus. Finally, annual energy performance (AEP) was adopted for a standardized energy efficiency evaluation of various venetian blinds products, and the sensitivity analysis of AEP to various parameters was conducted to identify the key parameters. The results indicated that by adjusting the key parameters of the venetian blinds, cooling energy saving can reach 44% and the heating energy saving can be up to 65%. The significant energy saving potential of venetian blinds indicates the prospect and importance of their use in residential buildings.

A novel optimization of the particle swarm based maximum power point tracking for photovoltaic systems under partially shaded conditions

<p><span lang="EN-US">When the irradiance distribution over the photovoltaic panels is uniform, the pursuit of the maximum power point is not reached, which has allowed several researchers to use traditional MPPT techniques to solve this problem Among these techniques a PSO algorithm is used to have the maximum global power point (GMPPT) under partial shading. On the other hand, this one is not reliable vis-à-vis the pursuit of the MPPT. Therefore, in this paper we have treated another technique based on a new modified PSO algorithm so that the power can reach its maximum point. The PSO algorithm is based on the heuristic method which guarantees not only the obtaining of MPPT but also the simplicity of control and less expensive of the system. The results are obtained using MATLAB show that the proposed modified PSO algorithm performs better than conventional PSO and is robust to different partial shading models.</span></p>

Approximate Image-Space Multidirectional Occlusion Shading Model for Direct Volume Rendering

Understanding and perceiving three-dimensional scientific visualizations, such as volume rendering, benefit from visual cues produced by the shading models. The conventional approaches are local shading models since they are computationally inexpensive and straightforward to implement. However, the local shading models do not always provide proper visual cues since non-local information is not sufficiently taken into account for the shading. Global illumination models achieve better visual cues, but they are often computationally expensive. It has been shown that alternative illumination models, such as ambient occlusion, multidirectional shading, and shadows, provide decent perceptual cues. Although these models improve upon local shading models, they still require expensive preprocessing, extra GPU memory, and a high computational cost, which cause a lack of interactivity during the transfer function manipulations and light position changes. In this paper, we proposed an approximate image-space multidirectional occlusion shading model for the volume rendering. Our model was computationally less expensive compared to the global illumination models and did not require preprocessing. Moreover, interactive transfer function manipulations and light position changes were achievable. Our model simulated a wide range of shading behaviors, such as ambient occlusion and soft and hard shadows, and can be effortlessly applied to existing rendering systems such as direct volume rendering. We showed that the suggested model enhanced the visual cues with modest computational costs.

Solar shading and multi-zone thermal simulation: Parsimonious modelling at urban scale

With the growing interest in urban scale simulation, urban building energy modelling tools (UBEM) are being developed. The purpose of these UBEM tools is to tackle multiple issues that can range from buildings retrofit potential to the sizing of thermal and/or electrical network or to the assessment of renewable energy sources potential. Unlike the modelling of a single building, collecting accurate building information data at district scale is nearly impossible and therefore the uncertainties increase. In this context, the selection of the most relevant and adequate models with regard to the available data and simulation objectives is challenging, and often a trade-off between accuracy and parametrization feasibility has to be found. A novel approach is proposed to choose the right level of model complexity for thermal heating demand simulation in buildings at district or city scale, by assessing in particular the impact of different thermal zoning methods with the UBEM tool DIMOSIM. This method for assessing the parsimony in modelling is applied to a selection of models from the literature in order to find a compromise between the available data, the different modelling levels of detail, the expected output and the computation time, according to district and buildings characteristics. By applying this approach, it has been found that a division per floor for building modelling is in most cases the most parsimonious choice for thermal heating demand simulation at district scale. Eventually, the coupling between thermal zoning models and solar shading models is analysed through the same methodology for assessing the modelling parsimony. The results show that the combination of simpler models (in particular a thermal zone per floor or mono-zone buildings for thermal zoning models, and a solar shading coefficient calculated per floor or facade for solar models) can be parsimonious enough to be used to determine the annual heating demand, speeding up strongly the simulation at the same time.

ShadingNet: Image Intrinsics by Fine-Grained Shading Decomposition

In general, intrinsic image decomposition algorithms interpret shading as one unified component including all photometric effects. As shading transitions are generally smoother than reflectance (albedo) changes, these methods may fail in distinguishing strong photometric effects from reflectance variations. Therefore, in this paper, we propose to decompose the shading component into direct (illumination) and indirect shading (ambient light and shadows) subcomponents. The aim is to distinguish strong photometric effects from reflectance variations. An end-to-end deep convolutional neural network (ShadingNet) is proposed that operates in a fine-to-coarse manner with a specialized fusion and refinement unit exploiting the fine-grained shading model. It is designed to learn specific reflectance cues separated from specific photometric effects to analyze the disentanglement capability. A large-scale dataset of scene-level synthetic images of outdoor natural environments is provided with fine-grained intrinsic image ground-truths. Large scale experiments show that our approach using fine-grained shading decompositions outperforms state-of-the-art algorithms utilizing unified shading on NED, MPI Sintel, GTA V, IIW, MIT Intrinsic Images, 3DRMS and SRD datasets.

Variational formulation of a hybrid perspective shape from shading model

Over a long period of time, it is challenging to solve the completed shape from shading (SFS) problem which has no limitations on light position and surface roughness. Many existing researches developed Hamilton–Jacobi equation (HJE)-based method of such SFS problem. However, HJE-based methods have one major weakness of boundary condition requirement. Finding a proper algorithm for calculating direct depth in a completed SFS model is desirable. In this paper, a completed hybrid perspective shape from shading model based on Cook–Torrance BRDF reflectance model is established. The depth is expressed and calculated directly on the Cartesian coordinates rather than spherical coordinates, which prevents exponential explosion risks caused by substitution of natural exponential. A direct variational formulation method is employed to solve the complex partial differential equation (PDE) of the image irradiance model. The major contribution of the method is that depth is considered as the only variable to deduce iterative equation. After discretizing the partial derivative terms of the iterative equation, the variational method could be programed conveniently and intuitively. Simulations and experiments demonstrate the accuracy and robustness of the method.

Model-based analysis of shading losses in ground-mounted photovoltaic power plants

Ground-mounted PV plants with multiple parallel mounting structure rows became the most common type of PV systems, where the shading of the adjacent rows results in significant energy losses. This paper presents a detailed modelling method of the inter-row shading to calculate irradiance distribution along the width of the PV rows. A modification of the Hay transposition model is proposed to account for the shading of the sky diffuse, circumsolar, and ground-reflected irradiance components. The effect of the uneven irradiance on the power output is considered by the cellwise calculation and aggregation of the I-V characteristics. The method is demonstrated by a case study, where the annual energy production and the reflection, shading, and cable losses are calculated for different string arrangements and row spacings. The proposed detailed shading model is compared to a simple shading calculation, where only the shading of the beam irradiance is considered. This simple method underestimates the shading losses by 50–80%, which underlines the importance of the proper calculation of the diffuse irradiance masking losses. The electrical mismatch losses due to the shading are compared for different string arrangements, where the best arrangement is also influenced by the number of the maximum power point trackers. As a general conclusion, the modules at the same height should be connected to the same string to minimise the shading losses. The presented method can improve the accuracy of PV simulations and the optimisation of the shading-related design parameters, like the module orientation and row spacing.

A GAN-based temporally stable shading model for fast animation of photorealistic hair

We introduce an unsupervised GAN-based model for shading photorealistic hair animations. Our model is much faster than previous rendering algorithms and produces fewer artifacts than other neural image translation methods. The main idea is to extend the Cycle-GAN structure to avoid semitransparent hair appearance and to exactly reproduce the interaction of the lights with the scene. We use two constraints to ensure temporal coherence and highlight stability. Our approach outperforms and is computationally more efficient than previous methods.

Cloud shadow detection removal for satellite supportive health care systems: research solution towards Australian Bushfire

Shadows limit numerous remote detecting applications, for example, characterization, target identification, and change discovery. Shadow recognition in high spatial goals remote detecting image is basic for finding land targets. Most current shadow location techniques use the histogram edge of unearthly qualities to recognize the shadows and nonshadows legitimately called hard parallel shadow. In this paper, we proposed another shadow identification calculation utilizing the HSI shading model and Daubechies complex wavelet change (DCWT). Since the pixel grid is a largescale framework, in the event that we apply calculation legitimately on the crude pixel space, it will be calculation escalated to compute the likeness network. Clearly, the exhibition of edge put together techniques vigorously depend with respect to the chose limit. All the while, these limit based strategies do not consider any spatial data. To beat these weaknesses, a delicate shadow portrayal strategy is created by bringing the idea of darkness into shadow identification, and technique is proposed so as to utilize neighborhood data. To take care of this issue, we isolate the lattice into a few squares and afterward applying calculation to distinguish shadows in H, S and I segments individually. At that point, three identified images are melded to get a last shadow recognition result. Near tests are performed for Kmeans and edge division techniques. The trial results show that higher discovery precision of the proposed approach is acquired, and it can take care of the issues of bogus excusals of K-means and limit division technique. Tests on remote detecting images have demonstrated that the proposed technique can acquire progressively precise identification results.

SREVAS: Shading Based Surface Refinement under Varying Albedo and Specularity

Shape-from-shading and stereo vision are two complementary methods to reconstruct 3D surface from images. Stereo vision can reconstruct the overall shape well but is vulnerable in texture-less and non-Lambertian areas where shape-from-shading can recover fine details. This paper presents a novel, generic shading based method to refine the surface generated by multi-view stereo. Different from most of the shading based surface refinement methods, the new development does not assume the ideal Lambertian reflectance, known illumination, or uniform surface albedo. Instead, specular reflectance is taken into account while the illumination can be arbitrary and the albedo can be non-uniform. Surface refinement is achieved by solving an objective function where the imaging process is modeled with spherical harmonics illumination and specular reflectance. Our experiments are carried out using images of indoor scenes with obvious specular reflection and of outdoor scenes with a mixture of Lambertian and specular reflections. Comparing to surfaces created by current multi-view stereo and shape-from-shading methods, the developed method can recover more fine details with lower omission rates (6.11% vs. 24.25%) in the scenes evaluated. The benefit is more apparent when the images are taken with low-cost, off-the-shelf cameras. It is therefore recommended that a general shading model consisting of varying albedo and specularity shall be used in routine surface reconstruction practice.

Effects of shading model and opacity on depth perception in optical see‐through augmented reality

AbstractAugmented reality (AR) technologies create an immersive environment by augmenting the real world with rendered virtual objects. One of the key requirements of an AR system is to understand how users perceive the depth of an AR object. Perceived distances to AR objects can be based on various depth cues such as rendering method used for the virtual object. The existing researches on the shading model and opacity mainly focus on the shape perception or the position relationship of several virtual objects in the virtual environment. We predicted that shading models and opacity would impact a user's estimation of a virtual object's depth in AR. We conducted two experiments to investigate the impact of color, size (Experiment 1), shading model, and opacity (Experiment 2) on the depth perception in an optical see‐through head‐mounted display (HMD). We found that the virtual object's color and size impact estimation efficacy. An interaction effect between color and size was also found. The results showed that shading models with specular highlights could help to improve depth perception in AR. Additionally, users had the lowest matching error when the opacity of a virtual object was 0.8.

Study on the impact of window shades’ physical characteristics and opening modes on air conditioning energy consumption in China

• A shading schedule of residential buildings is obtained through 949 questionnaires. • Two opening modes of window shades were considered. • Analyzed the six physical characteristics of window shades on energy consumption. • The results could allow design guidelines for developing the performance of window shades. This paper focused on the impact of window shades’ physical characteristics and opening modes on annual air conditioning energy consumption of residential buildings in China. Three building models with different window layouts were proposed initially, and then validated by the dimensionless indicator annual energy performance (AEP) to determine the final building model adopted in this study. Harbin, Beijing, Guangzhou, Changsha and Kunming were selected to represent five different climate zones in China. The shading model has taken six physical characteristics of window shades, viz. outer emissivity, inner emissivity, solar transmittance, solar reflectance, thermal infrared transmittance, conductivity and two opening modes, viz. up & down mode as well as left & right mode, into consideration. Besides, the window shades operation schedule was summarized through 949 valid questionnaires. The annual air conditioning energy consumption was calculated via EnergyPlus software, and then the impact of the above different opening modes and parameters on energy use were investigated. The analysis results indicated that the top & bottom opening mode is better than the left & right mode when used in Harbin, and the effect of two different modes in air conditioning energy consumption in Kunming is similar. But in the other three cities, the left and right mode is preferred. Besides, the analysis results of the impact of different physical characteristics on air conditioning energy use in different climate zones could help improve the energy performance of window shades.

Shading simulation for two photovoltaics solar generation residential systems (SPV) using SAM (System Advisor Model)

In this document, shading models are developed for photovoltaic solar generationsystems located in two environments, a rural one, in the Cundiboyacense savanna,and the other one within the con-urban area of the Colombian capital. Both systemsconsider a typical electrical load for an average home. The photovoltaic generationsystems and their components are dimensioned based on this estimation, for which,in this case, there are not considered any battery energy storage system. Shading onthe panels is done using SAM, inserting objects of considerable height in both environments.The results of this modeling confirm that indeed, power losses are greaterwhen considering the area of panels affected by shade. Therefore, a comparative simulationcase is presented for the two considered environments, including and excludinglosses due to the effect of shading, and the respective conclusions for this researchare finally written. Keywords: Renewable Energies, Photovoltaic Solar Energy, Losses, System AdvisorModel, Simulation, Shading.

Origins of Global Illumination.

Global illumination refers to a complete shading model that simulates real lighting and reflection as accurately as possible. Whether used for product prototyping or special effects for entertainment, the goal is to match the appearance of the real world. The origins of global illumination come at the intersection of a steady progression of shading models with the ancient simulation technique of ray tracing.

Uncertainty of Energy and Economic Performance of Manual Solar Shades in Hot Summer and Cold Winter Regions of China

Occupant behavior is recognized as a major source of discrepancy between simulated and actual energy consumption. This study investigates the uncertainty of energy and economic performance of manual solar shades for the south facade. A developed stochastic model for manual solar shades based on a discrete-time Markov chain method was constructed in Building Controls Virtual Test Bed (BCVTB) for co-simulation with EnergyPlus. The stochastic shade model was compared with deterministic models concerning energy savings potential and life cycle economic performance at different building scales (i.e., from a single room to a whole building). The results show that annual energy uncertainty, due to occupant behavior, on manual shades can be neglected at the building level, whereas for sizing heating equipment, energy uncertainty should be considered. The payback period for manual shades is about 10 years and, in general, a larger building has a higher economic performance. Comparative analysis shows that there is a relatively big performance overestimation or underestimation by commonly used deterministic models in building simulation tools, and thus may lead to a biased economic analysis or even an inappropriate design decision when comparing different energy-saving measures.

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.