lec07_panoramas - CS6670:ComputerVision NoahSnavely

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Lecture 7: Panoramas and stitching CS6670: Computer Vision Noah Snavely What’s inside your fridge? http://www.cs.washington.edu/education/courses/cse590ss/01wi/
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Announcements Project 1 due tonight by 11:59pm Upload to CMS. If you haven’t been added to CMS, let me know right away Next week: guest lecturer, Prof. Pedro Felzenszwalb, U. Chicago
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Announcements Project 2 will be released on Tuesday You can work in groups of two Send me your groups by Friday evening Adarsh will demo the project sometime next week (TBA)
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Readings Szeliski, Chapter 9.3
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Last time: projecting images onto a common plane mosaic PP each image is warped with a homography Can’t create a 360 panorama this way…
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Panoramas What if you want a 360 ° field of view? mosaic Projection Sphere
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Map 3D point (X,Y,Z) onto unit sphere Spherical projection X Y Z unit sphere unwrapped sphere Convert to spherical coordinates Spherical image Convert to spherical image coordinates s defines size of the final image » often convenient to set s = camera focal length Map image point to a ray in the world
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Unwrapping a sphere Credit: JHT’s Planetary Pixel Emporium
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Unwrapping a sphere Credit: JHT’s Planetary Pixel Emporium
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+ + + + Microsoft Lobby: http://www.acm.org/pubs/citations/proceedings/graph/258734/p251 szeliski Spherical panoramas
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Different projections are possible
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Spherical panoramas
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f = 200 (pixels) Spherical reprojection Map image to spherical coordinates* using inverse warping need to know the focal length input f = 800 f = 400 *assuming the horizon is in the middle of the image, i.e. φ =0
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Aligning spherical images Suppose we rotate the camera by θ about the vertical axis How does this change the spherical image? What if we don’t know R ?
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Aligning spherical images Suppose we rotate the camera by θ about the vertical axis How does this change the spherical image? Translation by This means that we can align spherical images by translation (This doesn’t quite work out if we rotate by φ about a horizontal axis)
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Image alignment Given two images in spherical coordinates, how do we compute the translation that aligns them?
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lec07_panoramas - CS6670:ComputerVision NoahSnavely

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