영상 기반 표현

(image Based Representation)

중앙대학교

CG Lab.

류승택

2000. 9. 14

Introduction

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3D model-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

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Traditional Modeling and Rendering

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Image based Modeling and Rendering

영상 기반 분류

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영상기반 표현 방법

(Image Based Representation)

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

Image Based Modeling:

The Chevette Project

Image Based Modeling:

The Campanile Movie

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Overview

 사진으로부터 모델을 복원  2 차원 이미지로부터 모델의 3 차원 공간정보획득

Image Based Rendering:

The Plenoptic Function

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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

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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

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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

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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

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가상공간의 실시간 탐색을 위한 연구

 가상공간을 높은 화질로 표현하기 위해서는 복잡하고 많은 양 의 모델이 필요  실시간 탐색이 어려움 • • • 보이는 물체만을 렌더링 (Visibility Culling) 가까운 거리에서는 실제 Geometry Model 사용 먼거리에 있는 물체에 대해 – LOD(Level Of Detail) 를 적용하거나 – Image 로 대치 시킴 (Image Based Representation)

Image Based Acceleration:

Image Based Primitives

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Hybrid Approach

 Sprite  Imposter  Nailboards  Portal Texture  image caches

Image Based Lighting:

Global Illumination

Others:

Tour into the picture

Others:

Multiple Center of Projection Images

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Overview

 Strip 카메라로부터 획득한 MCOP Image 를 이용하여 영상표현

Acquiring MCOP Image

Others:

Making face

Art:

Virtual Camera

 

Array of pictures taken onto same roll of film Playback achieves “frozen time” effect

Art:

The Matrix

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Applied Techniques

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photogrammetric modeling, projective texture-mapping Also applied in shots of the Tom Cruise film Mission Impossible II.

Graphics and Vision Technique

Appearance based

Lumigraph and light field Multiview Stereo

image

Image morphing Planar sprites Sprites Sprites with depth Layered depth image Optical flow estimation Plane sweep stereo Triangle scan conversion View dependent textures Texture mapping Geometric level of detail

Physically Geometric model based

Global illumination Radiosity Monte Carlo ray tracing

Graphics

Texture recovery Range data merging Silhouettes to volume Illumination estimation 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 SIGGRAPH '95 PROCEEDING, 1995, pp 39--46.

rendering system." 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”, 1997 년 (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)