• 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.

• Journal of Korea Game Society
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• v.20 no.3
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• pp.75-84
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• 2020

This paper introduces an interactive indirect illumination algorithm which considers indirect visibility. First, a small number of rays are emitted on hemisphere of the current pixel to obtain the first intersection. If this point is directly illuminated by the light source, its illuminated color is collected. Second, in order to approximate the indirect visibility, a 3D ray marching algorithm, which is based on a hierarchy structure, is used to accelerate the ray-voxel intersection. Third, the indirect images are denoised by an edge-avoiding filtering with a local means replacement method.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.33-38
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• 2008

본 논문은 핀홀 카메라 모델에 의해 렌더링한 컬러와 깊이 이미지의 후처리에 의한 실시간 필드심도 렌더링 방법을 제안한다. 필드심도 렌더링은 최근의 향상에도, 큰 스케일의 블러링에 필요한 계산 때문에 실용적으로 사용되지 못해 왔다. 본 방법은 이방성 가우시안 필터로 생성된 밉맵 이미지들을 비선형으로 보간하여 필드심도 효과에 필요한 블러링을 수행한다. 모든 계산 과정은 GPU로 가속되어, 안정적이고 확장 가능한 실시간 수행 성능을 확보한다. 또한, 후처리 방식의 두 가지 결점인 강도 누출과 블러링 불연속성을 이방성 가우시안 필터와 블러링 정도를 부드럽게 하여 제거한다. 본 방법은 뛰어난 실시간 성능과 함께 고품질의 필드심도 효과를 생성한다.

• Journal of Korea Game Society
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• v.11 no.1
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• pp.131-138
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• 2011

Recently in terrain rendeing, most researches introduce mipmap-based out-of-core methods for handling large sized DEM data which does not fit in main memory of general computer. However, mipmap-based LOD(level-of-detail) methods occur geometric errors which appear in data simplifying the higher LOD level. These geometric errors cause geometric popping effects where LOD level changes when viewpoint moves. In this paper, we propose vertex cohesion map for reducing geometric error. In preprocessing step, we generate vertex cohesion map, which is a texture that stores the vectors. By these vectors, each vertex will be cohered into the position in which the difference of gradient value is bigger than others. Therefore in terrain rendering, using vertex cohesion map can dramatically reduce the geometry popping effects rather than using mipmap.

• Journal of the Korea Computer Graphics Society
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• v.17 no.1
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• pp.25-31
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• 2011

Photomosaic is a method of representation an input image in forms of mosaics by a set of small tile images. Generally, equal rectangular tiles are used in photo mosaics. Therefore, there are limitations to expression of mosaic according to characteristic of images. In this paper, photo mosaics using quad-tree structure is proposed to create tiles in varies sizes. Initially, color variance per each level of an input image is computed using the mipmap of graphic hardware. Depending on the value of Valiance, the input image is divided into tiles in varies sizes. Each tile finds the most similar reference image and replaces with it. As a result, the method provides another pictorial effectiveness by dividing the input image into tiles in varies sizes depending on color held by the input image. In addition, whole processing is done on the graphic hardware and thereby we achieve faster performance.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.228-237
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• 2007

displacement mapping enables us to add realistic details to polygonal meshes without changing geometry. We present a real-time artifacts-free inverse displacement mapping method. In each pixel, we construct a ray and trace the ray through the displacement map to find an intersection. To skip empty regions safely, we traverse the image pyramid of displacement map in top-down order. Furthermore, when the displacement map is enlarged, intersection with bilinear interpolated displacement map can be found. When the displacement map is at distance, our method supports mipmap-like prefiltering to enhance image quality and speed. Experimental results show that our method can produce correct images even at grazing view angles. Rendering speed of a test scene is over hundreds of frames per second and the influence of resolution of displacement map to rendering speed is little. Our method is simple enough to be added to existing virtual reality systems easily.

• Journal of Korea Game Society
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• v.8 no.3
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• pp.61-68
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• 2008

Quadtree-based terrain visualization methods have been used in a lot of applications. However, because most procedures are performed on the CPU, the rendering speed is slow in comparison to methods using GPU. In this paper, we present a quadtree-based terrain visualization method working on the GPU with specially designed data structure, error-texture and LOD-texture, and block-based acceleration method. In preprocessing step, we calculate errors in world space and store them to error-texture. In rendering step, we examine projected errors of error-texture and choose the detail level, then store the projected errors to LOD-texture. View frustum culling is performed as block unit using the values of error-texture and LOD-texture. This method reduces CPU load and performs time consuming jobs such as LOD selection and view frustum culling.