Papers by Hoshang Kolivand
Abstract—Traditional interaction devices such as computer mice and keyboards do not adapt very we... more Abstract—Traditional interaction devices such as computer mice and keyboards do not adapt very well to immersive environments, since they were not necessarily designed for users who may be standing or in movement. Moreover, in the current interaction model for immersive environments, based on wands and 3D mice, a change of context is necessary in order to execute non-immersive tasks. These constant context changes from immersive to 2D desktops introduce a rupture in user interaction with the application.
This paper proposes a real-time software for outdoor rendering to control the shadow's position w... more This paper proposes a real-time software for outdoor rendering to control the shadow's position with effect of sun's position. The position of sun plays an important rule for outdoor games. Calculation of sun's position, as a result, position and length of shadows require a lot of attention and preciseness. Julian dating is used to calculate the sun's position in the virtual dome. In addition, of computer graphics, building design is another field that this paper contributes on it. To create shadow, projection shadow is proposed. By calculating the sun's position in the specific date, time and location on the earth, shadow is generated. Length and angle of shadow are two parameters measured for building design and both of them are calculated in this real-time application. Therefore, it can be used for teachers to teach some part of physics about earth orbit and it can be used in building design and commercial games in virtual reality systems.
This study will provide an overview of popular and famous algorithms and techniques in shadow gen... more 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.
Soft shadow with respect to the sun's position in virtual environments is a fascinating topic in ... more Soft shadow with respect to the sun's position in virtual environments is a fascinating topic in outdoor rendering. A coherent mathematic formula to create shadow with respect to the sun's position in specific location, date and time can make outdoor rendering as easy as indoor rendering. A target of this study is to propose a new coherent formula to do this. Outdoor rendering using a coherent formula will eliminate worrying about the sun's position and shadow status during the daytime. Low frames per second (FPS) in real-time rendering is a crucial problem in computer graphics, especially in soft shadow generation. A novel technique to create soft shadow in virtual environments is proposed. Geometric progression to select the color and a combination formula using sequence progression are proposed to determine the sample size. The new soft shadow generation, in addition to increasing FPS, enhances the quality of soft shadows. Finally, we strongly contend that the proposed technique can be used in commercial gaming and virtual reality systems.
2011 Workshop on Digital Media and Digital …, Jan 1, 2011
This paper introduced new real-time application for outdoor computer graphic programming to contr... more This paper introduced new real-time application for outdoor computer graphic programming to control the amount of shadow with effect of sun's position. The position of sun plays an important rule for outdoor games. Calculation of sun's position, as a result, position and length of shadows require a lot of attention and preciseness. Julian dating is used to calculate the sun's position in the virtual dome. In addition, of computer graphics, building design is another field that this paper contributes on it. To create shadow, projection shadow is proposed. By calculating the sun's position in the specific date, time and location on the earth, shadow is generated. Length and angle of shadow are two parameters measured for building designers and both of them are calculated in this proposed real-time application. Therefore, it can be used for teachers to teach some part of physics about earth orbit and effect of sun on shadow and it can be used in building design and commercial games in virtual reality systems.
Visual Informatics: Sustaining Research and …, Jan 1, 2011
In this paper a new algorithm to recognize occluder silhouette for generating shadow volume with ... more In this paper a new algorithm to recognize occluder silhouette for generating shadow volume with some improvement of the traditional shadow volume algorithm is proposed. Silhouette detection is one of the expensive processes of volume shadows (VS). The triangular algorithm and visiblenon-visible algorithm that are famous algorithms to detect the outline of occluder are renewed. An accurate comparison between these algorithms and a new algorithm has been done. The algorithm involves to detect silhouette and decreases the cost of implementation of VS. The obtained results confirm superiority of the proposed algorithm in terms of processing time to the previously used traditional algorithms. The last volume shadow algorithm using stencil buffer is rewritten and an algorithm for VS with silhouette detection together is proposed. It makes higher the number of frame per second.
Journal of Computer …
Problem statement: Shadows are most important effect to make realistic games and visually appeali... more Problem statement: Shadows are most important effect to make realistic games and visually appealing images, but they are poor in frame per second. Silhouette detection is most important phases to create real-time shadow. Approach: Present study describes a real-time shadow generated with volume shadow algorithm using Visible-Non Visible algorithm (VNV) in virtual environment illuminated by a movable light source to improve the frame per second. Silhouette detection that is most expensive part of shadow creation was described. Triangular method and VNV method were compared. An improved algorithm for volume shadow was proposed and volume shadow using both methods in C++ Opengl implemented. Results: The VNV algorithm increases the number of Frame Per Second (FPS) and as a result decreases the cost of implementation. Conclusion: A verified algorithm for volume shadow makes it easy to understand by everyone how to produce real-time shadow in outdoor and indoor virtual environment. It is possible to use it in current commercial games or other virtual reality systems.
In this paper we describe a real-time shadow generation with volume shadow algorithm in virtual e... more In this paper we describe a real-time shadow generation with volume shadow algorithm in virtual environment that is illuminated by light sources with possibility to move separately. This algorithm uses the combination of stencil and Z-buffers to generate shadow volume. It is simple to understand and implement. We have significantly improved and implemented recent techniques that are used in shadow volume algorithms using stencil buffers especially in order to recognize silhouette, reduce the number of shadow polygons and also redundant length of each triangles that makes the volume shadow. This work may be applied in commercial games or other virtual reality systems.
sersc.org
This paper describes one of the best methods to generate real-time shadow that called volume shad... more This paper describes one of the best methods to generate real-time shadow that called volume shadow. Volume shadow algorithm is possible to implement for virtual environment with moveable illuminated light source. We improve to find silhouette and implementation of the last techniques used in shadow volume algorithms, and limitation of length of volume of each semi-polygon that makes between silhouette's edge and shadow receiver. We rewrite the last volume shadow algorithm using stencil buffer and propose a pseudo code in OpenGl. The best tools that we have used in this algorithm are stencil buffer and Z-buffer.It makes realistic commercial games or it can be use in virtual reality systems.
ijvr.org
In shadow volume, the most expensive computation is silhouette detection. In this paper, the tria... more In shadow volume, the most expensive computation is silhouette detection. In this paper, the triangular algorithm (TA) and visible-non-visible (VnV) algorithm that are famous algorithms to detect the outline of occluder are renewed. In this paper, we proposed a hybrid algorithm based on TA and VnV, namely Hybrid Silhouette Detection (HSD) algorithm. HSD is an improved algorithm that can recognize silhouette for generating real-time shadow volume. Our algorithm involves detecting silhouette and decreases the cost of implementation for shadow volume rendering. The last shadow volume algorithm using stencil buffer is rewritten and an algorithm for shadow volume using HSD with respect of culling invisible parts of scene is proposed. An accurate mathematical comparison between TA, VnV and HSD algorithms is undertaken. The obtained results confirm superiority of our proposed algorithm in terms of processing and rendering time. Our algorithm can be used in virtual environment to increase the frame per second and to enhance the realistic of games programming.
ijcsi.org
This paper proposes a real-time software for outdoor rendering to control the shadow's position w... more This paper proposes a real-time software for outdoor rendering to control the shadow's position with effect of sun's position. The position of sun plays an important rule for outdoor games. Calculation of sun's position, as a result, position and length of shadows require a lot of attention and preciseness. Julian dating is used to calculate the sun's position in the virtual dome. In addition, of computer graphics, building design is another field that this paper contributes on it. To create shadow, projection shadow is proposed. By calculating the sun's position in the specific date, time and location on the earth, shadow is generated. Length and angle of shadow are two parameters measured for building design and both of them are calculated in this real-time application. Therefore, it can be used for teachers to teach some part of physics about earth orbit and it can be used in building design and commercial games in virtual reality systems.
Software Engineering and …, Jan 1, 2011
In this paper we describe a real-time shadow generation with volume shadow algorithm in virtual e... more In this paper we describe a real-time shadow generation with volume shadow algorithm in virtual environment that is illuminated by light sources with possibility to move separately. This algorithm uses the combination of stencil and Z-buffers to generate shadow volume. It is simple to understand and implement. We have significantly improved and implemented recent techniques that are used in shadow volume algorithms using stencil buffers especially in order to recognize silhouette, reduce the number of shadow polygons and also redundant length of each triangles that makes the volume shadow. This work may be applied in commercial games or other virtual reality systems.
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Papers by Hoshang Kolivand