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CS 563 Advanced Topics in Computer Graphics Introduction To IBR. By Cliff Lindsay. Slide Show ’99 Siggraph[6]. What Is IBR?. IBR: Multidisciplinary field that includes computer vision and graphics Techniques that replace and/or augment polygon models - PowerPoint PPT Presentation
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CS 563 Advanced Topics in Computer GraphicsIntroduction To IBR
By Cliff Lindsay
Slide Show ’99 Siggraph[6]
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]
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
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
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]
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
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
Texturing Mapping
Texture Space (u,v) 3D Object Space (x0, y0, z0) Screen Space (x, y) [5]
Texture mapping has close ties to Image Warping
Wide Industry Support (hardware and Software)
Filtering
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
Billboards
Billboards: Oriented toward viewer Matrix transformations (classical pipeline) Special effects (lens flares, laser/light bursts, etc) Hard to render objects (clouds, fire, smoke)
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))
Billboard Example
Billboard Example
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]
[7]
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)
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
Lumigraph/Light Fields 3
Sample of the objects on the plane are not continuos
Gaps are Created
[10]
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]
Lumigraph/Light Fields 5
[10]
Lumigraph/Light Fields 6
Example Rendering
[10]
View Interpolation
Reference Image 1 Reference Image 2
CorrespondingPixels
Morph maps
Based on diagrams from Watt[8]
View Morphing - more to come next presentation!
View Morphing
View Morphing - more to come next presentation!
View Morphing[9]
View Morphing
I0 I1
I0 ' I1 'Is '
I s
1 1
2 2
3
View Morphing - more to come next presentation!
View Morphing[9]
Recent Developments & The Future of IBR
Surface Light fields High Dynamic Range Radiance Maps View-dependent texture-mapping (VDTM) IBO (Image Based Objects)
Conclusion
Rendering time is decoupled from scene complexity
Images are used as input
Pre-calculation of scene data/images
Additional Resources
http://citeseer.nj.nec.com/cs - NEC Digital Library
http://www.siggraph.org http://www.debevec.org/ (View Morphing, High
Dynamic Range Radiance Maps, Projective Texture-Mapping)
http://www-2.cs.cmu.edu/%7Eph/869/www/misc.html (a cool site with a bunch of IBR links)
http://www.peter-oel.de/ibmr-focus/ (Another cool site)
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, 2nd 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