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More single view geometry
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  1. More single view geometry Describes the images of planes, lines,conics and quadrics under perspective projection and their forward and backward properties

  2. Camera properties • Images acquired by the cameras with the same centre are related by a plane projective transformation • Image entities on the plane at infinity, pinf , do not depend on camera position, only on camera rotation and internal parameters, K

  3. Camera properties 2 • The image of a point or a line on pinf , depend on both K and camera rotation. • The image of the absolute conic, w , depends only on K; it is unaffected by camera rotation and position. • w = ( KKT )-1

  4. Camera properties 2 • w defines the angle between the rays back-projected from image points • Thus camera rotation can be computed from vanishing points independent from camera position. • In turn, K may be computed from the known angle between rays; in particular, K may be computed from vanishing points corresponding to orthogonal scene directions.

  5. Perspective image of points on a plane

  6. Action of a projective camera on planes

  7. Action of a projective camera on lines

  8. Action of a projective camera on lines

  9. Line projection

  10. Action of a projective camera on conics

  11. Action of a projective camera on conics 2

  12. On conics

  13. Images of smooth surfaces

  14. Images of smooth surfaces 2

  15. Contour generator and apparent contour: for parallel projection

  16. Contour generator and apparent contour: for central projection

  17. Action of a projective camera on quadrics • Since intersection and tangency are preserved, the contour generator is a (plane) conic. Thus the apparent contour of a general quadric is a conic, so is the contour generator.

  18. Result 7.8

  19. On quadrics

  20. Result 7.9 • The cone with vertex V and tangent to the quadric is the degenerate quadric • QCO = (VT QV) Q – (QV)(QV)T • Note that QCOV = 0, so that V is the vertex of the cone as assumed.

  21. The cone rays of a quadric

  22. The cone rays with vertex the camera centre

  23. Example 7.10

  24. The importance of the camera centre

  25. The camera centre

  26. Moving image plane

  27. Moving image plane 2

  28. Moving image plane 3

  29. Camera rotation

  30. Example

  31. (a), (b) camera rotates about camera centre. (c) camera rotates about camera centre and translate

  32. Synthetic views

  33. Synthetic views. (a) Source image(b) Frontal parallel view of corridor floor

  34. Synthetic views. (a) Source image(c) Frontal parallel view of corridor wall

  35. Planar panoramic mosaicing

  36. Three images acquired by a rotating camera may be registered to the frame of the middle one

  37. Planar panoramic mosaicing 1

  38. Planar panoramic mosaicing 2

  39. Planar panoramic mosaicing 3

  40. Projective (reduced) notation

  41. Moving camera centre

  42. Parallax • Consider two 3-space points which has coincident images in the first view( points are on the same ray). If the camera centre is moved (not along that ray), the iamge coincident is lost. This relative displacement of image points is termed Parallax. • An important special case is when all scene points are coplanar. In this case, corresponding image points are related by planar homography even if the camera centre is moved. Vanishing points, which are points on pinf are related by planar homography for any camera motion.

  43. Motion parallax

  44. Camera calibration and image of the absolute conic

  45. The angles between two rays

  46. The angle q between two rays

  47. Relation between an image line and a scene plane

  48. The image of the absolute conic

  49. The image of the absolute conic 2

  50. The image of the absolute conic 3