1 / 27

CS 563 Advanced Topics in Computer Graphics Introduction To IBR

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

emery
Download Presentation

CS 563 Advanced Topics in Computer Graphics Introduction To IBR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. CS 563 Advanced Topics in Computer GraphicsIntroduction 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 (x0, y0, z0)  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

  13. 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] [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 View Morphing - more to come next presentation! Reference Image 1 Reference Image 2 Corresponding Pixels Morph maps Based on diagrams from Watt[8]

  22. View Morphing View Morphing - more to come next presentation! View Morphing[9]

  23. View Morphing View Morphing - more to come next presentation! 3 1 1 2 2 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://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)

  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, 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

More Related