• Journal of Korea Game Society
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• v.14 no.2
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• pp.77-84
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• 2014

Presence of soft shadow effects from an area light makes virtual scenes look more realistic. However, since computation of soft shadow effects takes a long time, acceleration methods are required to apply it to real-time 3D applications. Many researches assumed that area lights are white rectangles. We suggest a new method which renders soft shadows under the area light source having arbitrary shape and color. In order to approximate visibility test, we use a shadow mapping result near a pixel. Complexity of shadow near a pixel is used to determine degree of precision of our visibility estimation. Finally, our method can present more realistic soft shadows for the area light that have more general shape and color in real-time.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.628-630
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• 2000

3D 컴퓨터 그래픽스에서 그림자는 매우 중요한 요소이다. 그림자가 없으며 물체와 물체간의 정확한 위치를 파악하기가 어렵기 때문이다. 즉 물체가 다른 물체에 바로 붙어 있는지 조금 떨어져 있는지를 알아내기가 곤란한 것이다. 이러한 그림자의 중요성에도 불구하고 현존하는 3D 가속 하드웨어들은 그림자의 생성을 전혀 지원하지 못하고 있다. 또한, 이것을 보완하기 위해 많은 그림자 생성 알고리즘들이 제시되었지만 모두 그 한계가 명확하였다. 많은 그림자 생성 기법 중 텍스춰 하드웨어를 이용한 그림자 지도 기법은 광원과 물체가 고정되어 있을 경우 매우 빠른 속도로 그림자를 생성시킬 수 있지만 과원이나 물체가 움직일 경우에는 속도가 느려지게 된다. 본 논문에서는 그림자 지도 기법에 영상기반 렌더링 기법을 적용하여 실시간으로 그림자를 생성하고자 하였다. 본 논문의 기법은 매우 많은 메모리를 필요로 하기 때문에 데이터를 적당히 샘플링하여 웨이블릿 기반 압축 기법으로 압축하였고, 그림자를 생성할 때는 가장 가까운 저장된 그림자들을 2차원 보강하였다.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.806-810
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• 2006

The research of computer graphics is divided into two parts of photorealistic rendering and non-photorealistic rendering. The purpose of non-photo realistic rendering is to make image like cartoon, water-color, hatching etc. In this paper, we study for real-time hatching rendering and shadow techniques and we combine two techniques to make real-time hatching shadow. In shadow techniques we apply projected texture shadow to hatching rendering. Eventually, we introduce natural real-time hatching shadow through comparison and analysis.

• Journal of the Korea Computer Graphics Society
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• v.14 no.1
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• pp.11-16
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• 2008

This paper introduces a novel real-time soft shadowing method applicable for height maps. As well as supporting self-shadowing of the height map, our method allows shadows to be caught on other objects. The method is very suitable for dynamically changing height maps because it requires no precomputation. A shadow height map (SHM) is a new structure which represents the height of the shadow at each discretized coordinate of a height map. Constructing the SHM is O(n), where n is the number of texels in the SHM. Shadow can be computed from this map quickly and simply, using a pixel shader. Examples demonstrate good real-time performance and plausible visual quality.

• Journal of the Korea Computer Graphics Society
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• v.7 no.1
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• pp.27-35
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• 2001

Shadows are important elements in producing a realistic image. In rendering. generation of the exact shape and position of shadow is crucial in providing the user with visual cues on the scene. While the shadow map technique quickly generates a shadow for the scene wherein objects and light sources are fixed. it gets slow down as they start to move. In this paper. we apply an image-based rendering technique to generate shadows in real-time using graphics hardware. Due to the heavy requirement of storage for a shadow map repository. we use a wavelet-based compression scheme for effective compression. Our method will be efficiently used in generating realistic scenes in many real-time applications such as 3D games and virtual reality systems.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.5
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• pp.245-256
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• 2002

Shadows are important elements in producing a realistic image. Generation of exact shapes and positions of shadows is essential in rendering since it provides users with visual cues on the scene. It is also very important to be able to create soft shadows resulted from area light sources since they increase the visual realism drastically. In spite of their importance. the existing shadow generation algorithms still have some problems in producing realistic shadows in real-time. While image-based rendering techniques can often be effective1y applied to real-time shadow generation, such techniques usually demand so large memory space for storing preprocessed shadow maps. An effective compression method can help in reducing memory requirement, only at the additional decoding costs. In this paper, we propose a new image-barred shadow generation method based on image warping. With this method, it is possible to generate realistic shadows using only small sizes of pre-generated shadow maps, and is easy to extend to soft shadow generation. Our method will be efficiently used for generating realistic scenes in many real-time applications such as 3D games and virtual reality systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.574-578
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• 2009

Real-time object detection for distinguishing a moving object of interests from the background image in still image or video image sequence is an essential step to a correct object tracking and recognition. Moving cast shadow can be misclassified as part of objects or moving objects because the shadow region is included in the moving object region after object segmentation. For this reason, an algorithm for shadow removal plays an important role in the results of accurate moving object detection and tracking systems. To handle with the problems, an accurate algorithm based on the features of moving object and shadow in color space is presented in this paper. Experimental results show that the proposed algorithm is effective to detect a moving object and to remove shadow in test video sequences.

• Journal of the Korea Computer Graphics Society
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• v.6 no.4
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• pp.9-14
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• 2000

Non-Photorealistic rendering techniques, such as toon rendering, can enhance the quality of hand-drawn cell-animation images greatly with less effort. For this reason, to on rendering is one of the popular techniques used in the cell-animation image production field. The existing toon rendering techniques, however, have not been effective enough for the real-time image processing that the techniques have not been adequate for some processes that needs immediate responses such as virtual-realities, or video games. This paper will suggest the real-time toon rendering to overcome the limits through real-time outline detection and phong shading. In addition, a effective result-image is created as adding a shadow and a execution time remains by real-time through fast shadow generation algorithm.

• Journal of the Korea Computer Graphics Society
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• v.23 no.3
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• pp.55-64
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• 2017

In this paper, a novel soft shadow method is suggested to support realistic shadows in mobile ray tracing. In ray tracing, soft shadow is generally generated by sampling a shadow ray. As this sampling method increases the number of rays to be processed, it has undermined the performance. We designed the proposed soft shadow processing method and hardware architecture to overcome this problem through selective shadow generation and triangle address caching for minimizing the performance degradation caused by sampling. The proposed hardware architecture can be integrated into a mobile ray-tracing hardware and was evaluated in terms of its performance on the FPGA. Based on the results, the rendering performance about 4, 8, and 16 samples were improved, respectively, by 40%, 50%, and 56% on average compared to the previous method, and it was found that the real-time soft shadow processing is feasible with the proposed hardware architecture.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.506-515
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• 2007

In this paper, we propose a Real-time Interactive Shadow Avatar(RISA) which can express facial emotions changing as response of user's gestures. The avatar's shape is a virtual Shadow constructed from the real-time sampled picture of user's shape. Several predefined facial animations overlap on the face area of the virtual Shadow, according to the types of hand gestures. We use the background subtraction method to separate the virtual Shadow, and a simplified region-based tracking method is adopted for tracking hand positions and detecting hand gestures. In order to express smooth change of emotions, we use a refined morphing method which uses many more frames in contrast with traditional dynamic emoticons. RISA can be directly applied to the area of interface media arts and we expect the detecting scheme of RISA would be utilized as an alternative media interface for DMB and camera phones which need simple input devices, in the near future.