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Architectural Walkthroughs. CG Lab 박사 3 차 류승택. 발표 내용. 가상공간에서의 실시간 렌더링 관련 논문 (UNC) “Architectural Walkthroughs Using Portal Textures”, 1997 년 (IEEE Visualization 97) “3D Image Warping in Architectural Walkthroughs”, 1998. 3 (VRAIS ‘98)
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Architectural Walkthroughs CG Lab 박사 3차 류승택
발표 내용 • 가상공간에서의 실시간 렌더링 • 관련 논문 (UNC) • “Architectural Walkthroughs Using Portal Textures”, 1997년 (IEEE Visualization 97) • “3D Image Warping in Architectural Walkthroughs”, 1998. 3 (VRAIS ‘98) • “Efficient Warping for Architectural Walkthroughs using LDIs”, 1998. 10 (IEEE Visualization 98) • “Image for Accelerating Architectural Walkthroughs”, 1998. 12 (CG&A)
기본 개념 • High quality architectural walkthroughs require large and complex models • reducing rendering time • Subdividing it into cells and portals • Using Portal Culling • do not reduce the amount enough • Portal Texture • the use of images at portals as replacements for the geometry seen through the portal
Portal Culling vs Portal Texture <Portal Culling> <Portal Texture>
Portal Texture • Portal Texture의 표현 • using conventional texture • using image based rendering • using image warping • using Layered Depth Image
Conventional texture: Constrained Model • Define values • Viewing Height • Sampling Distance • Transition Distance • Viewing Angles
Conventional texture: visibility-determination algo. Visibility(cell, frustum) { Mark cell visible Cull cell to frustum Foreach portal { Cull portal to frustum if (portal is visible) { if (portal in transition) Initialize transition else if (portal is texture) Choose best texture sample else if (portal is geometry) Visibility(portal’s adjacent cell, culled frustum) } if (portal in transition) { Next transition step if (portal->texture finished) Choose best texture sample if (texture->portal finished) Visibility(portal’s adjacent cell, culled frustum) } } }
Conventional Texture : Problem • Texture • single texture • 커다란 그림이 벽에 걸려 있는 듯한 느낌 • Multiple textures • switch between them as we move • disadv: • popping effect, motion parallax • solution • image warping
Portal Warping: Image Warping • Image Warping
Solution increase the number of reference image per portal warp multiple reference images three visibility cases both reference image contains information about the same geometry one image contains information absent from the other image resolve visibility----> use z-buffering information about some geometry is missing from both images Portal Warping: Exposure
Portal Warping: Problem • Problem • Incorrect visibility • Do not guarantee correct visibility when multiple images are warped to the desired view • using expensive z-buffering • redundant works • warping two images incurs redundant work since many of the samples are identical.
Layered Depth Images • Construction LDIs • central image is stored in the LDI • remaining images are warped to the plane of the central image • sample lands at an empty location • Store • sample lands at an occupied location • store only if it represents a different surface • Threshold or Color • Warping LDIs • it behaves like like a single image when warped
