• Title/Summary/Keyword: 부드러운 그림자

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A Real-time Soft Shadow Rendering Method under the Area Lights having an Arbitrary Shape (임의의 모양을 가지는 면광원 하의 실시간 부드러운 그림자 생성 방법)

  • Chun, Youngjae;Oh, Kyoungsu
    • 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.

Mipmap-Based Deferred Soft Shadow Mapping (밉맵 기반의 지연된 부드러운 그림자 매핑)

  • Kim, Sunggoo;Lee, Sungkil
    • Journal of KIISE
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    • v.43 no.4
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    • pp.399-403
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    • 2016
  • Deferred Shading is a shading technique that postprocesses pixels in the screen space, following geometry-only rendering passes with depth buffering. Unlike typical shadow mapping techniques, this technique allows us to render shadows from multiple light sources without changing the structure of the rendering pipelines. This paper presents a deferred shadow mapping technique and its extension to soft shadows using mipmapping. Our technique first generates visibility maps from light sources, and blurs the visibility maps for deferred shading. This strategy leads to efficient soft-edged shadows, but does not incorporate depth variation, producing light bleeding to some extent. In order to suppress the light-bleeding artifacts, we also propose a depth-adaptive mipmap sampling technique in the screen space.

Real-Time Shadow Generation using Image Warping (이미지 와핑을 이용한 실시간 그림자 생성 기법)

  • Kang, Byung-Kwon;Ihm, In-Sung
    • 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.

Real-time Soft Shadowing of Dynamic Height Map Using a Shadow Height Map (그림자 높이 맵을 이용한 실시간 그림자)

  • Lee, Sung-Ho;Kim, Chang-Hun
    • 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.

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Real-time Soft-shadow using Shadow Atlas (그림자 아틀라스를 이용한 부드러운 그림자 생성 방법)

  • Park, Sun-Yong;Yang, Jin-Suk;Oh, Kyoung-Su
    • Journal of the Korea Computer Graphics Society
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    • v.17 no.2
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    • pp.11-16
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    • 2011
  • In computer graphics, shadows play a very important role as a hint of inter-object distance as well as themselves in terms of realism. To represent shadows, some traditional methods such as shadow mapping and shadow volume have been frequently used for the purpose. However, the rendering results are not natural since they assume the point light. On the contrary, an area light can render soft-shadows, but its computation is too burdensome due to integral over the whole light source surface. Many alternatives have been introduced, back-projection of occluder onto the light source to get visibility of light or filtering of shadow boundary by calculating size of penumbra. But they also have problems of light bleeding or ringing effects because of low order approximation, or low performance. In this paper, we describe a method to improve those problems using shadow atlas.

Shadow Removal from Scanned Documents taken by Mobile Phones based on Image Local Statistics (이미지 지역 통계를 이용한 모바일 기기로 촬영한 문서에서의 그림자 제거)

  • Na, Yeji;Park, Sang Il
    • Journal of the Korea Computer Graphics Society
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    • v.24 no.3
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    • pp.43-48
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    • 2018
  • In this paper, we present a method for removing shadows from scanned documents. Compared to the existing methods such as one based on image pyramid representation or adaptive thresholding, our method produces more robust and higher quality results. The basic idea of the approach is to use the local image statistics and to separate interesting regions from the image such as the regions around letters and figures. For the separated regions, we adaptively adjust the local brightness and contrast, and apply the sigmoid function to the intensity values as well to enhance the clarity of the image. For separated the other empty regions, we apply the gradient-base image hole filling method to fill the region with smooth color change.

Bounding Box based Shadow Ray Culling Method for Real-Time Ray Tracer (실시간 광선추적기를 위한 바운딩 박스 기반의 그림자 검사 컬링 기법)

  • Kim, Sangduk;Kim, Jin-Woo;Park, Woo-Chan;Han, Tack-Don
    • Journal of Korea Game Society
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    • v.13 no.3
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    • pp.85-94
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    • 2013
  • In this paper, we propose a scheme to reduce the number of shadow tests conducted during rendering of ray tracing. The shadow test is a very important process in ray tracing to generate photo-realistic images. In the rendering phase, the ray tracer determines whether to cull the shadow test based on information calculated from a shadow test conducted on the kd-tree in the preprocessing phase. In conventional rendering process, the proposed method can be used with little modification. The proposed method is suitable for a static scene, in which the geometry and light source does not change in the same manner as it does in the conventional method. The validity of the proposed scheme is verified and its performance is evaluated during cycle-accurate simulation. Through experiment results, we found that we could reduce up to 17% of the shadow test.

A Soft Shadow Technique for a Real-time Mobile Ray Tracing Hardware (실시간 모바일 레이트레이싱 하드웨어를 위한 소프트 쉐도우 생성 기법)

  • Kwon, Hyuck-Joo;Hong, Dukki;Park, Woo-Chan;Lee, Sanghoon
    • 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.

Fast Light Source Estimation Technique for Effective Synthesis of Mixed Reality Scene (효과적인 혼합현실 장면 생성을 위한 고속의 광원 추정 기법)

  • Shin, Seungmi;Seo, Woong;Ihm, Insung
    • Journal of the Korea Computer Graphics Society
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    • v.22 no.3
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    • pp.89-99
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    • 2016
  • One of the fundamental elements in developing mixed reality applications is to effectively analyze and apply the environmental lighting information to image synthesis. In particular, interactive applications require to process dynamically varying lighting sources in real-time, reflecting them properly in rendering results. Previous related works are not often appropriate for this because they are usually designed to synthesize photorealistic images, generating too many, often exponentially increasing, light sources or having too heavy a computational complexity. In this paper, we present a fast light source estimation technique that aims to search for primary light sources on the fly from a sequence of video images taken by a camera equipped with a fisheye lens. In contrast to previous methods, our technique can adust the number of found light sources approximately to the size that a user specifies. Thus, it can be effectively used in Phong-illumination-model-based direct illumination or soft shadow generation through light sampling over area lights.