Shadow Generation Algorithm Research Articles

Shadow mapping algorithms: Applications and limitations

This study provides an overview of popular and famous algorithms and techniques in shadow maps generation. Well- known techniques in shadow maps generation is described detail, along with a discussion of the advantages and drawbacks of each. Basic ideas, improvements and future works of the techniques are also comprehensively summarized and analyzed in depth. Often, programmers have difficulty selecting an appropriate shadow generation algorithm that is specific to their purpose. We have classifie d and systemized these techniques. The main goal of this paper is to provide researchers with background on a variety of shadow mapping techniques so as make it easier for them to choose the method best suited to their aims. It is al-so hoped that our analysis will help resea rchers find solutions to the shortcomings of each technique.

Shadow Rendering Technology in the Application of Virtual Simulation System

This thesis mainly discusses the basic theory of the real-time lighting and shadow and the application of virtual simulation system in the virtual simulation field, introduces the light model and shadow generation algorithm more detailedly which are applied in virtual simulation field virtual simulation system according to the actual situation finally.

Realistic real-time outdoor rendering in augmented reality.

Realistic rendering techniques of outdoor Augmented Reality (AR) has been an attractive topic since the last two decades considering the sizeable amount of publications in computer graphics. Realistic virtual objects in outdoor rendering AR systems require sophisticated effects such as: shadows, daylight and interactions between sky colours and virtual as well as real objects. A few realistic rendering techniques have been designed to overcome this obstacle, most of which are related to non real-time rendering. However, the problem still remains, especially in outdoor rendering. This paper proposed a much newer, unique technique to achieve realistic real-time outdoor rendering, while taking into account the interaction between sky colours and objects in AR systems with respect to shadows in any specific location, date and time. This approach involves three main phases, which cover different outdoor AR rendering requirements. Firstly, sky colour was generated with respect to the position of the sun. Second step involves the shadow generation algorithm, Z-Partitioning: Gaussian and Fog Shadow Maps (Z-GaF Shadow Maps). Lastly, a technique to integrate sky colours and shadows through its effects on virtual objects in the AR system, is introduced. The experimental results reveal that the proposed technique has significantly improved the realism of real-time outdoor AR rendering, thus solving the problem of realistic AR systems.

Shadow generation algorithm of augmented reality using adaptive sampling and fusion

Since the soft shadow achieved by the existing shadow generation algorithms of Augmented Reality(AR) is unrealistic,the authors proposed a shadow generation algorithm using adaptive sampling and background fusion.First,the authors computed shadow spatial location distribution of virtual objects by using planar shadow algorithm which took occlusion into account.Then,to improve the procedure of soft shadow generation in swell and erode algorithm,an adaptive sampling method which got illuminant union according to shape types was presented.Finally,since shadow color gotten by gray image method was limited to single channel,the authors presented a method based on multi-channel and background fusion.The experimental results show that in the proposed algorithm the color of soft shadow is more reasonable and the method of soft shadow rendering is more effective.Consequently,the presented algorithm improves the realism of soft shadow.

Survey of Shadow Volume Algorithms in Computer Graphics

This study will provide an overview of popular and famous algorithms and techniques in shadow generation based on shadow volumes. It characterizes well-known techniques, describing each of them in detail, and discusses the advantages and drawbacks of each. Basic ideas, improvements, and future works of the techniques are also comprehensively summarized and analyzed in depth. Often, programmers have difficulty selecting an appropriate shadow generation algorithm based on shadow volumes that is specific to their purpose. We have classified and systemized these techniques. The main goal of this paper is to provide researchers with background on a progress of shadow volume techniques so as to make it easier for researchers to choose the method best suited to their aims. It is also hoped that our analysis will help researchers find solutions to the shortcomings of each technique.

Dynamic Shadow Generation System Based on Shape Recognition

This paper proposes a dynamic shadow generation system that combines the shadow of an object with the artificial shadows of virtual characters. In our proposed system, infrared light is used to capture an object’s shadow in order to discriminate between a shadow generated by an object and a virtual shadow generated by the system. Our proposed system determines areas in which shadows do not appear and then the shadows of virtual characters are added to these areas. This paper presents the basic idea of the system, the shadow generation algorithm that it uses, and an empirical study on the sharpness of a generated shadow, along with the distance between an object and a screen used in this system.

AN OBJECT-ORIENTED APPROACH TO SHADOW GENERATION IN COMPUTER GRAPHICS

This paper presents an object-oriented shadow generation algorithm for a large number of convex polyhedra (objects) in a 3-D scene. In the past, the shadow volume binary space partitioning (SVBSP) tree algorithm is known to be efficient in a static environment in which the point light source can be changed. However, if a scene consists of many objects and each object consists of many polygons, the time complexity for generating and traversing an SVBSP tree increases rapidly because the SVBSP tree algorithm only deals with polygons which are components of objects. Furthermore, the SVBSP tree algorithm suffers from polygon-splitting problems resulting in a high cost as the number of polygons increases. Our approach is object-oriented in the sense that an object is used as the basic logical unit instead of polygons. In the preprocessing stage the object ordering for shadow generation is determined for all possible light source positions. At the run time, the shadow detection algorithm is executed, and if necessary, shadow fragments are generated. We also present an approach to retrieving, updating, and displaying a 3-D static or dynamic world which consists of a large number of objects.

Near real-time shadow generation using BSP trees

This paper describes an object-space shadow generation algorithm for static polygonal environments illuminated by movable point light sources. The algorithm can be easily implemented on any graphics system that provides fast polygon scan-conversion and achieves near real-time performance for environments of modest size. It combines elements of two kinds of current shadow generation algorithms: two-pass object-space approaches and shadow volume approaches. For each light source a Binary Space Partitioning (BSP) tree is constructed that represents the shadow volume of the polygons facing it. As each polygon's contribution to a light source's shadow volume is determined, the polygon's shadowed and lit fragments are computed by filtering it down the shadow volume BSP tree. The polygonal scene with its computed shadows can be rendered with any polygon-based visible-surface algorithm. Since the shadow volumes and shadows are computed in object space, they can be used for further analysis of the scene. Pseudocode is provided, along with pictures and timings from an interactive implementation.

Surface-Shadow Generation For The Preparation Of Synthetic Imagery

Shadows can add significant edge and surface detail to imagery and thus substantially increase the performance of automated correlation guidance systems. A shadow-generation algorithm was implemented to increase the accuracy of synthetic imagery used to simulate visible, near-infrared, and far-infrared sensors. Initially, a data base was established in which all surfaces were represented by a list of vertices and material codes and arranged according to a scheme of a priori masking priority. Each surface was then clipped against updated clipping polygons representing the silhouette of all previous surfaces that had higher masking priorities as viewed from the position of the light source. The resulting hidden surface was inserted into the data base and flagged as a shadow for gray-scale prediction by the appropriate sensor model. Because each surface is compared to a union of polygons rather than to individual surfaces, this algorithm is computationally efficient for use with large data bases.