Download presentation
Presentation is loading. Please wait.
1
CS 563 Advanced Topics in Computer Graphics Introduction To IBR By Cliff Lindsay Slide Show ’99 Siggraph[6]
2
What Is IBR? IBR: Multidisciplinary field that includes computer vision and graphics Techniques that replace and/or augment polygon models Primary data pre-rendered images and photographs as input The Rendering Spectrum [3]
3
Where Did IBR Come From? Photo-realism Modeling ability has been stifled by rendering advancements Availability of inexpensive digital image acquisition hardware Recent graphics accelerators trends Necessity to render object that can’t be rendered using polygons
4
Tenants and Common Techniques of IBR Rendering time is decoupled from scene complexity Images are used as input Exploits coherence Pre-calculation of scene data/images
5
Computer Vision Computer Graphics = IBR. Combining CG and Computer Vision Vision Technology Lacks robust Algorithms The Graphics Industry Needs better modelling Siggraph ’99 Course on Image-based Rendering[6]
6
How Does IBR Compare to Traditional Rendering? Image Warping Vs. Matrix Transformations Perspective Division Vs. Projective Normalization What the !@#$ Is A Splat Kernel? [1] Image from Leonard McMillan
7
Approaches 2D Approaches: Texture Mapping Sprite, Billboards, and Impostors Image Layering 3D approaches: LDI (2.5D) View Interpolation & Morphing Mosaics 4D approaches: The Lumigraph Light Fields
8
Texturing Mapping Texture Space (u,v) 3D Object Space (x 0, y 0, z 0 ) Screen Space (x, y) [5] Texture mapping has close ties to Image Warping Wide Industry Support (hardware and Software) Filtering
9
Sprites, Billboards, and Impostors (Oh my!) Sprites: Pure 2D image No warping, or projection (like mouse cursor) Billboards: Sprite applied to a polygon Alpha channel usually employed Uses texture mapping for acceleration Impostors: Billboards created on the fly. Can represent complex models Error metric associated w/ changed views
10
Billboards Billboards: Oriented toward viewer Matrix transformations (classical pipeline) Special effects (lens flares, laser/light bursts, etc) Hard to render objects (clouds, fire, smoke)
11
Impostors Impostor Techniques: Error Angle Off Screen Rendering Polygon Texturing Texture resolution need not exceed screen resolution texres = screenres * objsize/(2 * distance * tan(fov/2))
12
Billboard Example
14
Lumigraph/Light Fields 0 Plenoptic function An image is a collection of radiance values a long a ray. Radiance value for all possible rays = Plenoptic function 4D (for our purpose) [7]
15
Lumigraph/Light Fields 1 Represent an object by it’s extents Each point on a cube has multiple rays eminating. Each wall has 2 planes (12 planes make a cube)
16
Lumigraph/Light Fields 2 You parameterize a ray using the 2 planes L(s, t, u, v) = radiance for a ray Ray – plane intersection make it easy and fast
17
Lumigraph/Light Fields 3 Sample of the objects on the plane are not continuos Gaps are Created [10]
18
Lumigraph/Light Fields 4 Continuos luminance is a linear sum B – basis function for which we can calculate at grid points If we use a constant value, the coefficient take on the values of the grid points [10]
19
Lumigraph/Light Fields 5 [10]
20
Lumigraph/Light Fields 6 Example Rendering [10]
21
View Interpolation Reference Image 1Reference Image 2 Corresponding Pixels Morph maps Based on diagrams from Watt[8] View Morphing - more to come next presentation!
22
View Morphing View Morphing - more to come next presentation! View Morphing[9]
23
View Morphing 11 2 2 3 View Morphing - more to come next presentation! View Morphing[9]
24
Recent Developments & The Future of IBR Surface Light fields High Dynamic Range Radiance Maps View-dependent texture-mapping (VDTM) IBO (Image Based Objects)
25
Conclusion Rendering time is decoupled from scene complexity Images are used as input Pre-calculation of scene data/images
26
Additional Resources http://citeseer.nj.nec.com/cs - NEC Digital Library http://citeseer.nj.nec.com/cs http://www.siggraph.org http://www.siggraph.org http://www.debevec.org/ (View Morphing, High Dynamic Range Radiance Maps, Projective Texture- Mapping) http://www.debevec.org/ http://www-2.cs.cmu.edu/%7Eph/869/www/misc.html (a cool site with a bunch of IBR links) http://www-2.cs.cmu.edu/%7Eph/869/www/misc.html http://www.peter-oel.de/ibmr-focus/ (Another cool site) http://www.peter-oel.de/ibmr-focus/
27
References [1] McMillan, Leonard, “An Image-Based Approach to Three-Dimensional Computer Graphics ”,, http://graphics.laces.mitt.edu/~mcmillan/IBRwork/defense23.html, date unknown, Cited slide #6. [2] McMillan, Leonard, Gortler, Steven, “Applications of Computer Vision to Computer Graphics”, ACM Siggraph, Vol. 33 no. 4, Nov. 99 [3] Akenine-Moller, Tomas, Haines, Eric, “Real-Time Rendering, 2 nd Edition”, A K Peters, 2002 [4] Watt, Alan, “3D Computer Games”, Addison-Wesley Pub Co, Volume 1, 2nd edition, 1999 [5] Heckbert, Paul S., “Survey of Texture Mapping,” IEEE Computer Graphics & Applications, Cited slide #10, November 1986, [6] Cohen, Michael, “Course on Image-based, Modeling, Rendering, and Lighting”, Siggraph ‘99 [7] Mcmillian, Leonard, Bishop, Gary, “Plenoptic Modeling: An Image-Based Rendering System”, Proceedings of SIGGRAPH 95, (Los Angeles, CA August 6-11, 1995), pp. 39-46 [8] Watt, Alan, “3D Computer Graphics”, Addison-Wesley Pub Co, 3nd edition (), 2000 [9] Chen, S.E., Williams L., “View Interpolation for Image Synthesis”, ACM Siggraph ’95 [10]Gortler, S, Cohen, M, Girzesczuk, R, Szeliski, R, “The Lumigraph”, ACM Siggraph, 1996
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.