영상 기반 표현 (image Based Representation) 중앙대학교 CG Lab. 류승택 2000. 9. 14

Introduction 3D model-based Rendering Image-based Rendering Explicit use of 3 Dimensional models Uses conventional rendering pipeline Speed dependent on scene complexity Relies on hardware accelerator for speed Requires sophisticated software for realism Image-based Rendering Directly uses collection of image Based on interpolation or pixel reprojection Speed independent on scene complexity Relies on processor speed Realism depends on input images

Traditional vs Image-based Representation Traditional Modeling and Rendering Image based Modeling and Rendering

영상 기반 분류 영상기반 표현 방법 (Image Based Representation) 영상기반 모델링 (Image Based Modelling) 2차원 영상으로부터 3차원 모델을 복원 및 표현 영상기반 렌더링 (Image Based Rendering) 2차원 영상들의 조합으로부터 새로운 시점의 영상 생성 영상기반 가속화 (Image Based Acceleration) 가까운 거리에서는 실제 Geometry Model 사용하고 먼 거리에 있는 물체에 대해 Image로 대치 시킴 영상기반 라이팅 (Image Based Lighting) 2차원 영상으로부터 조명 정보를 추출하여 새로운 광원을 부여

Image Based Modeling: The Chevette Project

Image Based Modeling: The Campanile Movie Overview 사진으로부터 모델을 복원 2차원 이미지로부터 모델의 3차원 공간정보획득

Image Based Rendering: The Plenoptic Function The light in a scene can be described by a multi-dimensional function infeasible since it would require measurements from all points of the scene and in all direction at all times

Image Based Rendering: Environment Map Mosaics (stitching) combination of at least two different images yield a higher resolution or larger image Environment Map reduce the dimensionality of the plenoptic function by restricting the observer to one point

Image Based Rendering: Light Field & Lumigraph Light Slab Two-plane Parameterization reducing the plenoptic function into a four-dimensional table Light flows from uv plane to st plane Planes in any position

Image Based Rendering: View Morphing Techniques for combining image Three steps Prewarp  Morph  Postwarp

Image Based Rendering: Layered Depth Image Sprite with Depth Layered Depth Image

Image Based Acceleration: Realtime Walkthru 가상공간의 실시간 탐색을 위한 연구 가상공간을 높은 화질로 표현하기 위해서는 복잡하고 많은 양의 모델이 필요 실시간 탐색이 어려움 보이는 물체만을 렌더링 (Visibility Culling) 가까운 거리에서는 실제 Geometry Model사용 먼거리에 있는 물체에 대해 LOD(Level Of Detail)를 적용하거나 Image로 대치 시킴 (Image Based Representation)

Image Based Acceleration: Image Based Primitives Hybrid Approach Sprite Imposter Nailboards Portal Texture image caches <Image Based Primitive>

Image Based Lighting: Global Illumination

Others: Tour into the picture

Others: Multiple Center of Projection Images Overview Strip카메라로부터 획득한 MCOP Image를 이용하여 영상표현 Acquiring MCOP Image

Others: Making face

Array of pictures taken onto same roll of film Art: Virtual Camera Array of pictures taken onto same roll of film Playback achieves “frozen time” effect

Applied Techniques Art: The Matrix photogrammetric modeling, projective texture-mapping Also applied in shots of the Tom Cruise film Mission Impossible II.

Graphics and Vision Technique Appearance based Physically based image Geometric model Triangle scan conversion Global illumination Lumigraph and light field Image morphing Sprites Sprites with depth Layered depth image Planar sprites View- dependent textures Geometric level of detail Monte Carlo ray tracing Texture mapping Radiosity Graphics Texture recovery Range data merging Silhouettes to volume Illumination estimation Multiview Stereo Optical flow estimation Plane- sweep stereo Layered stereo Depth map recovery Image mosaics Curves to 3D mesh Geometry fitting Reflection estimation Vision

참고문헌 Mcmillan, L. and Bishop, G. "Plenoptic modeling : An image-based rendering rendering system." SIGGRAPH '95 PROCEEDING, 1995, pp 39--46. Anders Gustafsson and Henrik Turbell, Image-Based Rendering, Linkoping University, Sweden, 1997 Sing Bing Kang, A Survey of Image-based Rendering Techniques, Technical Report, CRL 97/4, Digital Equipment Corp., Cambridge Research Lab, Cambridge, Mass., 1997. Leonard McMillian Jr, An Image-based Approach to three-dimensional computer graphics, PH.D. DISSERTATION, UNC-CH DEPT. OF COMPUTER SCIENCE, APRIL 1997. (PUBLISHED AS UNC COMPUTER SCIENCE TECHNICAL REPORT TR97-013) Christoph Bregler, Michael F. Cohen, Paul Debevec, Leonard McMillan, Francois X. Sillion, Richard Szeliski, Image-based Modeling, Rendering and Lighting, SIGGRAPH 99 Course note, 1999 Visual Navigation of Large Environments Using Texture Clusters, Paulo, 93 Dynamic Generated Imposter, Gernot Schaufler, 95 Efficient Imposter Manipulation for Real-Time Visualization of Urban Scenery, Francois Sillion, EG’ 97 Multi-Layered imposters for accelerated rendering, EG 99 “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)