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(A Survey on Image-based Rendering Techniques)

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1 (A Survey on Image-based Rendering Techniques)
计算机图形学学科研讨会 基于图像绘制(IBR)技术综述 (A Survey on Image-based Rendering Techniques) 石教英 浙江大学计算机学院 计算机辅助设计与图形学国家重点实验室 2005年5月

2 目 录 一、基于图像绘制(IBR)技术定义 二、典型IBR技术演示 三、IBR技术理论基础-Plenoptic Funciton
目 录 一、基于图像绘制(IBR)技术定义 二、典型IBR技术演示 1、Panorama Mosaics 2、Tour-Into-Picture 3、Light Field 4、Feature-based Morphing 三、IBR技术理论基础-Plenoptic Funciton 1、An introduction 2、how to handle with plenoptic fuction 四、IBR技术发展 1、Image Matting 2、Digital PhotoMontage 3、High-Dynamic-Range Image Display 4、Plenoptic photography 五、基于图像绘制技术定义的扩展

3 一、基于图像绘制(IBR)技术定义 Traditional Computer Graphics
Input: Geometry, Material Properties (Color, Reflectance,…etc.), Lighting. Transformation and Rasterization. Computer Vision methods to recover models. Transform (& Lighting) Rasterization

4 一、基于图像绘制(IBR)技术定义 Top Level Survey 3D Graphics Image-Based Rendering
Geometry or Surface Based Rendering & Modeling Sample-Based Graphics Image-Based Rendering & Modeling Volume Rendering

5 一、基于图像绘制(IBR)技术定义

6 一、基于图像绘制(IBR)技术定义 Why IBR? Problems of triangle-based graphics:
Always starts from scratch. Millions of sub-pixel triangles. Geometry IBR Modeling Difficult Easy Complexity #triangles #pixels Fidelity Synthetic Acquired

7 一、基于图像绘制(IBR)技术定义 Definition of IBR (by Sing Bing Kang) image-based rendering techniques rely on interpolation using the original set of input images or pixel reprojection from source images onto the target image in order to produce a novel virtual view

8 一、基于图像绘制(IBR)技术定义 Definition of IBR (by Cha Zhang & Tsuhan Chen of CMU) Given a continuous plenoptic function that describes a scene, image-based rendering is a process of two stages: – sampling and rendering. In the sampling stage, samples are taken from the plenoptic function for representation and storage. In the rendering stage, the continuous plenoptic function is reconstructed with the captured samples.

9 二、典型IBR技术演示 Paronoma Mosaics Demo

10 二、典型IBR技术演示 Tour-Into-Picture

11 二、典型IBR技术演示 Lightfield Video

12 二、典型IBR技术演示 Feature-based Morphing

13 三、IBR技术理论基础-Plenoptic Funciton
1. An Introduction Two ways of describing the world: A source description: ——The world can be described by geometric models, texture maps, refection models, lighting and shading models. An appearance description: ——The world can be described by the dense array of light rays filling the space, which can be observed by posing eyes or cameras in the space. The light rays can be represented through the Plenoptic function. The traditional model-based rendering approach adopts the source description method. The image-based rendering approach adopots the plenoptic function to describe the world.

14 三、IBR技术理论基础-Plenoptic Funciton
IBR: An Old Story Plenoptic function As pointed out by Adelson and Bergen (1991): The world is made of three-dimensional objects, but these objects do not communicate their properties directly to an observer. … The plenoptic function serves as the sole communication link between the physical objects and their corresponding retinal images. It is the intermediary between the world and the eye.

15 三、IBR技术理论基础-Plenoptic Funciton
7D Plenoptic Function

16 三、IBR技术理论基础-Plenoptic Funciton
2. How to Handle Plenoptic Function? Two Stages sampling and reconstruction of sampled signals Two directions for simplication Restrain the viewing space of the viewers View point Perceptual Introduce some source descriptions into IBR Geometry Depth

17 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 1: Wavelength Constant wavelength RGB Almost all the practical representations of IBR make this assumption.

18 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 2: Air Air is translucent Radiances along a light ray through empty space remain constant.

19 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 3: Time Static scene Images captured at different time and positions can be used together to render novel views. Too large size for dynamic scene

20 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 4: Viewpoint The viewer is constrained to be on a surface Acceptable: Human eyes are usually at a certain height-level Human eyes are less sensitive to vertical parallax and lighting changes

21 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 5: Viewpoint The viewer moves along a certain path. Reduces 2 dimensions from the full plenoptic function. Too large size for dynamic scene

22 三、IBR技术理论基础-Plenoptic Funciton
Restraining in View Space Assumption 6: Viewpoint The viewer has a fixed position. Reduces the dimension of the plenoptic function by 3. No 3D effects can possibly be perceived. Similarity to regular images and videos.

23 三、IBR技术理论基础-Plenoptic Funciton
Various Representations

24 三、IBR技术理论基础-Plenoptic Funciton
6D – The Surface Plenoptic Function Assumption 2. As we discussed, when radiance along a light ray through empty space remains constant. 6D Position on the surface (2D) Light ray direction(2D) Time (1D) and wavelength (1D).

25 三、IBR技术理论基础-Plenoptic Funciton
Example The surface light field could be considered as dimension-reduced version of SPF. D. N. Wood, D. I. Azuma, K. Aldinger, B. Curless, T. Duchamp, D. H. Salesin and W. Stuetzle, “Surface light fields for 3D photography”, Computer Graphics (SIGGRAPH’00), July 2000.

26 三、IBR技术理论基础-Plenoptic Funciton
5D – Plenoptic Modeling and Light field Video Plenoptic modeling, which is a 5D function 3D for the camera position, 2D for the cylindrical image. L. McMillan and G. Bishop, “Plenoptic modeling: an image-based rendering system”, Computer Graphics (SIGGRAPH’95), August 1995,

27 三、IBR技术理论基础-Plenoptic Funciton
Plenoptic Modeling To render a novel view from the 5D representation, the close-by cylindrical projected images are warped to the viewing position based on their epipolar relationship and some visibility tests.

28 三、IBR技术理论基础-Plenoptic Funciton
4D – Light field / Lumigraph Assumption 1, 2 and 3 Trickily parameterize ray space to 2-plane representation.

29 三、IBR技术理论基础-Plenoptic Funciton

30 三、IBR技术理论基础-Plenoptic Funciton
3D – Concentric Mosaics Assumption 1, 2, 3 and 4

31 三、IBR技术理论基础-Plenoptic Funciton
Camera Moving on a Plane Center camera => panorama Off-centered cameras => motion parallax Camera Beam Tripod

32 三、IBR技术理论基础-Plenoptic Funciton
Multi-perspective Image Top view Manifold mosaic

33 三、IBR技术理论基础-Plenoptic Funciton
Panorama from Slit Images Single perspective point …...

34 三、IBR技术理论基础-Plenoptic Funciton
Concentric Mosaics Mosaics at concentric circles

35 三、IBR技术理论基础-Plenoptic Funciton
Concentric Mosaics Render a novel image Top view

36 三、IBR技术理论基础-Plenoptic Funciton
2D – Image Mosaicing Composes one single mosaic with multiple input images In most cases, the light rays recorded in the mosaic share the same center-of-projection (COP) -Panoramic mosaic or panorama

37 三、IBR技术理论基础-Plenoptic Funciton
Examples

38 三、IBR技术理论基础-Plenoptic Funciton
2D – Image Mosaicing In the more general scenario, the cameras of the input images can move in free form and the resultant mosaic has MCOPs Manifold Mosaic.

39 三、IBR技术理论基础-Plenoptic Funciton
Examples

40 三、IBR技术理论基础-Plenoptic Funciton
Panoramic Cameras Rotating Cameras Kodak Cirkut Globuscope Stationary Cameras Be Here

41 三、IBR技术理论基础-Plenoptic Funciton
Quicktime VR Using environmental maps Cylindrical Cubic spherical At a fixed point, sample all the ray directions. Users can look in both horizontal and vertical directions

42 三、IBR技术理论基础-Plenoptic Funciton
Mars Pathfinder Panorama

43 三、IBR技术理论基础-Plenoptic Funciton
IBR with Various Source Descriptions

44 三、IBR技术理论基础-Plenoptic Funciton
Correspondence between Images

45 三、IBR技术理论基础-Plenoptic Funciton
Example 1: View Morphing (SIGGRAPH 96) Steve Seitz etc.

46 三、IBR技术理论基础-Plenoptic Funciton
Dense Depth Map

47 三、IBR技术理论基础-Plenoptic Funciton
Various Rendering Techniques Polygon Camera Planar Sprites LDI Sprite with Depth Viewing Region Environment Map

48 三、IBR技术理论基础-Plenoptic Funciton
Layered Depth Images Idea: Handle disocclusion Store invisible geometry in depth images

49 三、IBR技术理论基础-Plenoptic Funciton
Texture Map (+ Scene Geometry) Image based modeling View dependent texture mapping

50 三、IBR技术理论基础-Plenoptic Funciton
Reflection Models (+ Scene Geometry) Image based relighting

51 三、IBR技术理论基础-Plenoptic Funciton
Example: Image Based Relighting Siggraph Relighting.mov

52 三、IBR技术理论基础-Plenoptic Funciton
Turn to another question… What is the relationship between geometry and image based rendering? J. -X. Chai, X. Tong, S. –C. Chan, and H. –Y. Shum. Plenopic sampling. In Proc. SIGGRAPH, 2000

53 四、IBR技术发展 Digital image matting Interactive digital photomontage High-dynamic range image processing Light field photograph

54 四、IBR技术发展——Image matting
什么是抠图? 图像抽取的简称,是指把任意形状的前景物体从图像中抽取出来的一种技术。它与图像合成是一对互逆的操作。 [Porter84]

55 四、IBR技术发展——Image matting

56 四、IBR技术发展——Image matting

57 四、IBR技术发展——Image matting
一般来说,自然图像抠图可以分为区域分割、颜色估计与alpha估计三个步骤。主要存在两个问题: 计算前景与背景颜色分量的过程复杂,导致速度变慢 alpha估计方法不够鲁棒,以至抠图效果欠佳

58 四、IBR技术发展——Image matting
区域划分 抠图是个不可精确求解问题,对图像施加约束或提供人工交互是必然的 通过画前景和背景两条轮廓线把图像划分为前景、背景和未知三个区域

59 四、IBR技术发展——Image matting
颜色估计

60 四、IBR技术发展——Image matting
alpha估计(1) RGB颜色空间中的alpha估计 三通道加权法(Knockout) 投影法(Ruzon00,Hillman01,Chuang01)

61 四、IBR技术发展——Image matting
alpha估计(2) RGB颜色空间中的alpha估计

62 四、IBR技术发展——Image matting
alpha估计(3) 感知颜色空间中的alpha估计

63 四、IBR技术发展——Image matting
结果与比较(1) Bayesian Global Poisson 我们的方法

64 四、IBR技术发展——Image matting
结果与比较(2) Bayesian Global Poisson 我们的方法

65 四、IBR技术发展——Image matting
结果与比较(3)

66 四、IBR技术发展——Image matting
“GrabCut” —— Interactive Foreground Extraction using Iterated Graph Cuts Carsten rother, Vladimir Kolmogorov, Andrew Blake

67 四、IBR技术发展——Image matting

68 四、IBR技术发展——Image matting
Lazy Snapping Yin Li, Jian Sun, Chi-Keung Tang, Heung-Yeung Shum

69 四、IBR技术发展——Image matting

70 四、IBR技术发展——Interactive Digital Photomontage
An interactive computer-assisted framework for combining parts of a set of photographs into a single composite picture Two primary techniques Graph-cut optimization Gradient-domain fusion

71 四、IBR技术发展——Interactive Digital Photomontage

72 四、IBR技术发展——High-Dynamic Range Image Processing
如何在低动态范围的显示设备,如100:1的CRT上显示高动态范围(如25000:1)的图像 构造HDR Radiance Map,压缩之,显示在普通显示设备上 获得HDR Radiance Map的方法 拍几张曝光度不同的照片 拍全景视频

73 四、IBR技术发展——High-Dynamic Range Image Processing

74 四、IBR技术发展——High-Dynamic Range Image Processing
多次曝光法生成HDR radiance map

75 四、IBR技术发展——High-Dynamic Range Image Processing
用全景视频生成HDR radiance map

76 四、IBR技术发展——High-Dynamic Range Image Processing
LDR图像增强

77 四、IBR技术发展——Light Field Photography
Plenoptic camera

78 四、IBR技术发展——Light Field Photography
Plenoptic camera

79 292*292微镜图像构成完整的Light field图像。这些微镜图像反应出真实世界中光线的结构,从而包含了对象的深度信息。
左一,是焦平面前 左二,是焦平面后 左三,是焦平面上

80 四、IBR技术发展——Light Field Photography

81 四、IBR技术发展——Light Field Photography

82 四、IBR技术发展——Light Field Photography

83 五、基于图像绘制技术定义的扩展 基于图像的绘制(IBR)是一类产生新的视觉效果的图像采样和绘制技术。新的视觉效果包括:合成新视点和视角的视图(Paranoma mosaic, CM, Light field, View morphing, TIP),新的光照效果(IB relighting),合成新的图像(Image matting),交互式数字蒙太奇效果(Interactive digital photomontage ),扩大图像的动态深度(HDR),全光照相术(Light field photography),综合孔径共焦成像技术(Synthetic aperture confocal imaging)等效果。采样图像可以是真实世界的照相,也可以是计算机综合的图形。处理时可以完全不需要采样图像所含的辅助信息,也可以辅以一定的采样图像的几何、光照和纹理等信息,构成不同类型的IBR技术。

84 谢 谢


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