Shading Model Research Articles

Integrated Model for Shading and Airflow Window in BSk

Shading devices were investigated as a means to improve the energy performance of airflow windows in semi-arid climates (BSk), where ventilation is important for indoor comfort. According to previous research, louvers can improve energy efficiency. We have simulated an airflow window with integrated shading in the city of Yazd, Iran. Results obtained with EnergyPlus show that in comparison with common and double-glazed windows, airflow windows are more energy efficient. A network model was developed to take into account heat transfer in the integrated airflow window system.

Real-Time Cloth Rendering with Fiber-Level Detail.

Modeling cloth with fiber-level geometry can produce highly realistic details. However, rendering fiber-level cloth models not only has a high memory cost but it also has a high computation cost even for offline rendering applications. In this paper we present a real-time fiber-level cloth rendering method for current GPUs. Our method procedurally generates fiber-level geometric details on-the-fly using yarn-level control points for minimizing the data transfer to the GPU. We also reduce the rasterization operations by collectively representing the fibers near the center of each ply that form the yarn structure. Moreover, we employ a level-of-detail strategy to minimize or completely eliminate the generation of fiber-level geometry that would have little or no impact on the final rendered image. Furthermore, we introduce a simple self-shadow computation method that allows lighting with self-shadows using relatively low-resolution shadow maps. We also provide a simple distance-based ambient occlusion approximation as well as an ambient illumination precomputation approach, both of which account for fiber-level self-occlusion of yarn. Finally, we discuss how to use a physical-based shading model with our fiber-level cloth rendering method and how to handle cloth animations with temporal coherency. We demonstrate the effectiveness of our approach by comparing our simplified fiber geometry to procedurally generated references and display knitwear containing more than a hundred million individual fiber curves at real-time frame rates with shadows and ambient occlusion.

Effects of shading in summer and autumn on physiological and biochemical characteristics of 'Huangjinya' in Shandong Province, China

In order to ensure the suitable shade model for 'Huangjinya' tea plant in Shandong Province, black or blue shading net at 55%, 70% or 85% shading rates was selected to recover tea garden in summer and autumn, then micro-climate of tea garden, leaf color, chlorophyll fluorescence parameters, growth status and biochemical composition of tea shoots were investigated.The results showed that compared with the control, light intensity and air temperature in tea garden, leaf temperature of tea plants in different shading treatments significantly decreased, while air humidity in tea garden increased. The contents of chlorophyll in the tea leaves were obviously increased with increasing the shading rate, which resulted in the leaf color becoming green. The yellowing characteristics and biochemical quality of 'Huangjinya' tea plants could be well kept in 55% shading treatments. In 70% shading treatments, 'Huangjinya' tea plants had better growth situation and higher yield with no photo-inhibition. Compared with the blue shading treatments, black shading treatments could obviously promote the growth of 'Huangjinya' tea plants, keep yellowing characteristics, and improve the quality. Therefore, the 70% black shading treatment (daily PAR values of 1.2-3.5 ten thousand lx) was appropriate for promoting the growth of 'Huangjinya' tea plants at the seedling stage. For mature tea plants, the 55% black shading treatment (daily PAR values of 1.8-5.5 ten thousand lx) could be used to keep the yellowing characteristics and to improve biochemical quality effectively, so as to give full play to its variety characteristics, to achieve goal of high quality and high yield.

Geometry-based shading for shape depiction enhancement

Recent works on Non-Photorealistic Rendering (NPR) show that object shape enhancement requires sophisticated effects such as: surface details detection and stylized shading. To date, some rendering techniques have been proposed to overcome this issue, but most of which are limited to correlate shape enhancement functionalities to surface feature variations. Therefore, this problem still persists especially in NPR. This paper is an attempt to address this problem by presenting a new approach for enhancing shape depiction of 3D objects in NPR. We first introduce a tweakable shape descriptor that offers versatile functionalities for describing the salient features of 3D objects. Then to enhance the classical shading models, we propose a new technique called Geometry-based Shading. This technique controls reflected lighting intensities based on local geometry. Our approach works without any constraint on the choice of material or illumination. We demonstrate results obtained with Blinn-Phong shading, Gooch shading, and cartoon shading. These results prove that our approach produces more satisfying results compared with the results of previous shape depiction techniques. Finally, our approach runs on modern graphics hardware in real time, which works efficiently with interactive 3D visualization.

Refining Geometry from Depth Sensors using IR Shading Images

We propose a method to refine geometry of 3D meshes from a consumer level depth camera, e.g. Kinect, by exploiting shading cues captured from an infrared (IR) camera. A major benefit to using an IR camera instead of an RGB camera is that the IR images captured are narrow band images that filter out most undesired ambient light, which makes our system robust against natural indoor illumination. Moreover, for many natural objects with colorful textures in the visible spectrum, the subjects appear to have a uniform albedo in the IR spectrum. Based on our analyses on the IR projector light of the Kinect, we define a near light source IR shading model that describes the captured intensity as a function of surface normals, albedo, lighting direction, and distance between light source and surface points. To resolve the ambiguity in our model between the normals and distances, we utilize an initial 3D mesh from the Kinect fusion and multi-view information to reliably estimate surface details that were not captured and reconstructed by the Kinect fusion. Our approach directly operates on the mesh model for geometry refinement. We ran experiments on our algorithm for geometries captured by both the Kinect I and Kinect II, as the depth acquisition in Kinect I is based on a structured-light technique and that of the Kinect II is based on a time-of-flight technology. The effectiveness of our approach is demonstrated through several challenging real-world examples. We have also performed a user study to evaluate the quality of the mesh models before and after our refinements.

Enigmatic glacigenic ridges from the Odra Glaciation in the vicinity of Krzepice (Woźniki-Wieluń Upland, Poland)

Abstract The central part of the Woźniki-Wieluń Upland is characterised by mature old glacial landforms associated with the Middle- Polish Glaciations. In some areas, however, more pronounced post-glacial landforms can be observed that were remodelled by later morphogenetic processes to a lesser extent. To the south-east of Krzepice, in the vicinity of Dolisko, there is an extensive depression in which twelve parallel ridges can be found. In terms of their morphology and location as well as due to their relationship to the surrounding landforms, the ridges examined resemble forms that would be referred to as drumlins, glaciotectonic forms or glacial curvilineations in late glacial areas. The material presented is the result of the initial research stage. The studies conducted in this stage involved primarily geomorphological mapping supplemented by an analysis of landforms on a shaded relief model and on an orthophotomap. At the current stage of studies on the glacigenic landforms in the vicinity of Dolisko, three scenarios concerning their origins have been put forward that need to be verified. The first scenario involves glaciotectonic origins, the second assumes that they were formed in the same manner as classic drumlins, fluted moraines or longitudinal squeeze ridges, and the third scenario assumes that they have the same origins as glacial curvilineations. The group of glacigenic ridges discussed is a glacial landform unique in southern Poland.

Using Urban Development Boundaries to Constrain Uncontrolled Urban Sprawl in China

Based on constraining the spatial extent of urban expansion, the urban development boundary concept provides guidance on resource constraints and policy development for urban areas and aims to meet the new demands of urban development under the background of a new type of urbanization in China. We applied remote sensing and geographical information system (GIS) techniques, along with the slope, land use, exclusion, urban extent, transportation, and hill shade (SLEUTH) model, to identify urban growth boundaries in Changzhou City, China. We then comprehensively considered various land use regulation policies and the carrying capacity of land resources to construct an urban development boundary model. This model was tested using empirical data on the delineation of flexible and rigid urban development boundaries. We argue that China's position as the largest developing country in the world has resulted in significant uncertainties in its socioeconomic development; therefore, the construction of Chinese cities requires both flexible controls and a rigid management structure. The model developed in this study successfully meets the construction needs of China's urban development, particularly as it contains an optimal degree of generalizability.

A Practical and Controllable Hair and Fur Model for Production Path Tracing

AbstractWe present an energy‐conserving fiber shading model for hair and fur that is efficient enough for path tracing. Our model adopts a near‐field formulation to avoid the expensive integral across the fiber, accounts for all high order internal reflection events with a single lobe, and proposes a novel, closed‐form distribution for azimuthal roughness based on the logistic distribution. Additionally, we derive, through simulation, a parameterization that relates intuitive user controls such as multiple‐scattering albedo and isotropic cylinder roughness to the underlying physical parameters.

Guest Editorial: Shape Analysis Beyond the Eikonal Equation

“Shape Analysis” is an interesting research area which contains many thought-provoking problems and mathematical challenges, especially at the representation level. Shape of an object is considered as the enclosing surface (the boundary) or the enclosed interior. One of the major challenges is to define representations of “shapes” that can be manipulated by image processing methods. This is an important need in practice because more often than not shapes need to be extracted or recovered from raw images; moreover, the process of recovering shapes from raw images highly benefits from prior knowledge of candidate shapes. One of the key means of shape representation is the Euclidean Distance Transform (EDT), which is governed by the Eikonal Equation. The values of the EDT at each interior point give the distance to the nearest boundary point. This distance notion is used in almost any problem that requires integrating shape and image information; e.g., a rich variety of shape guided image-processing or shape extraction tasks. Especially in the 1990s, the idea of embedding shapes as zeros of the signed EDT is highly popularized by the level-set framework and its fast implementation, leading to a booming research area in implicit shape representations. However, as challenging problems are developed, formulations that move beyond the classical Eikonal Equation emerged. This special issue consists of six papers each exploring an interesting direction moving beyond the Eikonal formulation in the field of Shape Analysis. The first two papers, “Analysis and Approximation of some Shape–from–Shading Models for non-Lambertian Surfaces” and “A Unified Variational Volume Registration Method based on Automatically Learned Brain Structures”, deal with two key applications that jointly involve shapes and images. In the first paper, Silvia Tozza and Maurizio Falcone present a unified mathematical formulation of some non-Lambertian models, which lead to more complex stationary nonlinear partial differential equations of Hamilton-Jacobi type which can be regarded as a generalization of the classical Eikonal Equation corresponding to the Lambertian case. In the second paper, Carl Lederman et al. present an active volume technique employing level sets of the distance function. Unlike the common practice, the level sets in their formulation are only utilized on their respective regions and not on the whole domain, making the computations feasible as the number of regions increases. The next four papers propose alternative distance notions or computations. They are briefly discussed as follows. In “Affine Invariant Distance Using Multiscale Analysis”, Luis Alvarez et al. present a distance transform for planar shapes that is invariant under any planar projection of the

An Improved Method to Predict the Position of Maximum Power Point During Partial Shading for PV Arrays

For a photovoltaic (PV) system, it is widely assumed that the peaks of a partially shaded P–V curve are located at the multiples of $0.8{V_{{\text{oc}}}}$ , where ${V_{{\text{oc}}}}$ is the open-circuit voltage of the PV module. However, this assumption—known as the of $0.8{V_{{\text{oc}}}}$ model for partial shading—is not necessarily true. If the same model is used to design the maximum power point tracker (MPPT), it is very likely that the algorithm will scan the wrong region of the P–V curve and, hence, an incorrect global peak detection. This paper attempts to prove the inadequacy of the $0.8{V_{{\text{oc}}}}$ model when the number of modules in the string increases. Further, the work suggests a simple relationship to predict the correct position of the peaks. It is found that for a string of 20 modules ( ${V_{{\text{oc}}}}$ of 400 V), the maximum deviation between the actual and computed peak is less than 3 V, while for the $0.8{V_{{\text{oc}}}}$ model, the deviation reaches up to 50 V. In addition, using the proposed method, the MPPT efficiency can be improved by approximately 2%.

Order-Independent Transparency for Programmable Deferred Shading Pipelines

In this paper, we present a flexible and efficient approach for the integration of order-independent transparency into a deferred shading pipeline. The intermediate buffers for storing fragments to be shaded are extended with a dynamic and memory-efficient storage for transparent fragments. The transparency of an object is not fixed and remains programmable until fragment processing, which allows for the implementation of advanced materials effects, interaction techniques or adaptive fade-outs. Traversing costs for shading the transparent fragments are greatly reduced by introducing a tile-based light-culling pass. During deferred shading, opaque and transparent fragments are shaded and composited in front-to-back order using the retrieved lighting information and a physically-based shading model. In addition, we discuss various configurations of the system and further enhancements. Our results show that the system performs at interactive frame rates even for complex scenarios.

Reduction of Solar UV Radiation Due to Urban High-Rise Buildings--A Coupled Modelling Study.

Solar UV radiation has both adverse and beneficial effects to human health. Using models (a radiative transfer model coupled to a building shading model), together with satellite and surface measurements, we studied the un-obstructed and obstructed UV environments in a sub-tropical urban environment featured with relatively high pollution (aerosol) loadings and high-rise buildings. Seasonal patterns of the erythemal UV exposure rates were governed by solar zenith angles, seasonal variations of aerosol loadings and cloud effects. The radiative transfer modelling results agreed with measurements of erythemal UV exposure rates and spectral irradiances in UVA and UVB ranges. High-rise buildings and narrow road width (height to width, H/W, ratios up to 15) reduced the modelled total UV (UVA+UVB) radiation and leave 10% of the un-obstructed exposure rate at ground-level at noon. No more than 80% of the un-obstructed exposure rate was received in the open area surrounded by 20-storey buildings. Our modelled reduction of UVB radiation in the urban environment was consistent with similar measurements obtained for Australia. However, our results in more extreme environments (higher H/W ratios) were for the first time reported, with 18% of the un-obstructed exposure rate remained at the ground-level center of the street canyon.

INTERACTIVE NON-PHOTOREALISTIC RENDERING

Due to increasing demands of artistic style with Interactive Rate, we propose this review paper as a starting point for any person interested in researching of interactive non-photorealistic rendering. As a simple yet effective means of visual communication, interactive non-photorealistic rendering generates images that are closer to human-drawn than are created by traditional computer graphics techniques with more expressing meaningful visual information. This paper presents taxonomy of interactive non-photorealistic rendering techniques which developed over the past two decades, structured according to the design characteristics and behavior of each technique. Also, it covers the most important algorithms in interactive stylized shade and line drawing, and separately discussing their advantages and disadvantages. The review then concludes with a discussion of the main issues and technical challenges for Interactive Non-Photorealistic Rendering techniques. In addition, this paper discusses the effect of modified phong shading model in order to create toon shading appearance.

Realistic photometric stereo using partial differential irradiance equation ratios

Shape from shading with multiple light sources is an active research area and a diverse range of approaches have been proposed in the last decades. However, devising a robust reconstruction technique still remains a challenging goal due to several highly non-linear physical factors being involved in the image acquisition process. Recent attempts at tackling the problem via photometric stereo rely on simplified hypotheses in order to make the problem solvable. Light propagation is still commonly assumed to be uniformly oriented, and the BRDF assumed to be diffuse, with limited interest for materials giving specular reflection. Taking into account realistic point light sources, in this paper we introduce a well-posed formulation based on partial differential equations for both diffuse and specular shading models. We base our derivation on the popular approach of image ratios, which makes the model independent from photometric invariants. The practical effectiveness of our method is confirmed with a wide range of experiments on both synthetic and real data, where we compare favorably to the state of the art.

The use of screening effects in modelling route-based daytime road surface temperature

Winter road maintenance is essential for road safety. Accurate predictions of the road surface temperature (RST) and conditions can enhance the efficiency of winter road maintenance. Screening effects, which encompass shading effects and the influence of the sky-view factor (ψ s ), influence RST distributions because they affect road surface radiation fluxes. In this work, light detection and ranging (Lidar) data are used to derive shadow patterns and ψ s values, and the resulting shadow patterns are used to model route-based RST distributions along two stretches of road in Sweden. The shading patterns and road surface radiation fluxes calculated from the Lidar data generally agreed well with measured RST values. Variation in land use types and the angle between the road direction and solar azimuth may introduce uncertainties, and accounting for these factors may improve the results obtained in certain cases. A simple shading model that only accounts for the direct radiation at the instant of measurement is often sufficient to provide reasonably accurate RST estimates. However, in certain cases, such as those involving measurements close to sunset, it is important to consider the radiation accumulated over several hours. The inclusion of ψ s improves the model performance even more in such cases. Overall, RST models based on the accumulated direct shortwave radiation offered an optimal balance of simplicity and accuracy. General radiation models were built for country road and highway environments, explaining up to 70 and 65 %, respectively, of the observed variation in RST along the corresponding stretches of road.

Optimal displacement of photovoltaic array’s rows using a novel shading model

• Photovoltaic energy has experienced tremendous growth worldwide. • The position of the fixed panels presents the problem of shadowing among them. • A method to avoid shading is proposed. • The method is based on solar height, the latitude and the PV panel tilt. • Results indicating that the proposed method can reduce the area by up to 40%. Photovoltaic energy has experienced tremendous growth in terms of implementation at facilities for power supply in rural areas and for energy dispatch to grid. The relative position of the fixed panels can present the problem of varying amounts of shadowing among them, which can reduce the overall energy produced from the array of photovoltaic panels on specific dates and times, in addition to the problems in each of the panels themselves. The existing methods calculate the distances between the rows of PV panels using a fixed height of the sun, such that the rays always strike perpendicular to the panels, thereby limiting the duration of solar gain to 4 h. This paper proposes a method that optimises the minimisation of the distance between the rows of fixed photovoltaic panels. The proposed method is based on the exact calculation of the shadows of the panels for the different positions of the sun, which depends on the latitude of the facility, throughout the course of the day and for all of the planned hours of solar gain. To illustrate the proposed method, it has been applied to a case study for which the solutions obtained using the traditional methods are compared, indicating that the distance can be reduced by up to 40% when the tilt angle of the panel is 60°. In conclusion, the proposed general method for optimally minimising the distance between the PV panels in solar arrays, which is of particular interest for standalone photovoltaic (PV) systems in remote areas that act as isolated small power producing units for the supply of electricity.

Face Detection via Bayesian Model with Homogeneity Property

In this paper, a calculation for dividing skin districts in shading pictures utilizing shading and edge data is exhibited. Skin hued areas are initially recognized utilizing a Bayesian model of the human skin shading. These areas are further divided into skin district competitors that fulfill the homogeneity property of the human skin. We demonstrate that Bayesian skin shading model beats numerous different models, for example, the piece-wise straight models, Gaussian models and model in light of multilayer discernments. Test results show that the proposed division calculation decreases false location brought about by foundation pixels having skin hues, and all the more altogether it is fit for isolating genuine skin districts from dishonestly recognized areas.

Novel 3D Modelling System Capturing Objects with Sub-Millimetre Resolution

This paper presents novel 3D modelling system providing three-dimensional shaded models of objects, with representing brightness and smoothness of it's surface. Proposed device is based on laser scanner and robotic manipulator, which empowers high flexibility since it is programmable in 6 degrees of freedom. Exchangeable laser scanners empower capability of building models of both tiny detailed structures and large object. Device is primarily intended to use at health care domain, where it brings lot of expenses savings compared to presently used scanning systems, but it could be used in many other applications. Scanning system constitution, operation and parameters are discussed.

Optimal topology of urban buildings for maximization of annual solar irradiation availability using a genetic algorithm

An approach based on the optimal placement of buildings that favors the use of solar energy is proposed. By maximizing the area of exposure to incident solar irradiation on roofs and facades of buildings, improvements on the energy performance of the urban matrix are reached, contributing decisively to reduce dependence on other less environmentally friendly energy options. A mathematical model is proposed to optimize the annual solar irradiation availability where the placement of the buildings in urban environment favors the use of solar energy resource. Improvements on the solar energy potential of the urban grid are reached by maximizing the exposure of incident solar irradiation on roofs and facades of buildings. The proposed model considers predominant, the amount of direct solar radiation, omitting the components of the solar irradiation diffused and reflected. The dynamic interaction of buildings on exposure to sunlight is simulated aiming to evaluate the shadowing zones. The incident solar irradiation simulation and the dynamic shading model were integrated in an optimization approach implemented numerically. The search for optimal topological solutions for urban grid is based on a Genetic Algorithm. The objective is to generate optimal scenarios for the placement of buildings into the urban grid in the pre-design phase, which enhances the use of solar irradiation.

Novel real-time facial wound recovery synthesis using subsurface scattering.

We propose a wound recovery synthesis model that illustrates the appearance of a wound healing on a 3-dimensional (3D) face. The H3 model is used to determine the size of the recovering wound. Furthermore, we present our subsurface scattering model that is designed to take the multilayered skin structure of the wound into consideration to represent its color transformation. We also propose a novel real-time rendering method based on the results of an analysis of the characteristics of translucent materials. Finally, we validate the proposed methods with 3D wound-simulation experiments using shading models.