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Sensing and Perceiving Motion

Sensing and Perceiving Motion. Cmput 610 Martin Jagersand 2001. How come perceived as motion?. Im = sin(t)U5+cos(t)U6. Im = f1(t)U1+…+f6(t)U6. Counterphase sin grating. Spatio-temporal pattern Time t, Spatial x,y. Counterphase sin grating. Spatio-temporal pattern

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Sensing and Perceiving Motion

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  1. Sensing and Perceiving Motion Cmput 610 Martin Jagersand 2001

  2. How come perceived as motion? Im = sin(t)U5+cos(t)U6 Im = f1(t)U1+…+f6(t)U6

  3. Counterphase sin grating • Spatio-temporal pattern • Time t, Spatial x,y

  4. Counterphase sin grating • Spatio-temporal pattern • Time t, Spatial x,y Ignoring Phi: = +

  5. Notes: • Only one term: Motion left or right • Mixture of both: Standing wave • Direction can flip between left and right

  6. QT movie Reichardt detector

  7. Gradient: in Computer Vision Correlation: In bio vision Spatiotemporal filters: Unifying model Severalmotion models

  8. Spatial response:Gabor function • Definition:

  9. Temporal response: Adelson, Bergen ’85 Note: Terms from taylor of sin(t) Spatio-temporal D=DsDt

  10. Receptor response toCounterphase grating • Separable convolution

  11. Simplified: • For our grating: (Theta=0) • Write as sum of components: = exp(…)*(acos… + bsin…)

  12. Space-time receptive field

  13. Combined cells • Spat: Temp: • Both: • Comb:

  14. Result: • More directionally specific response

  15. Energy model: • Sum odd and even phase components • Quadrature rectifier

  16. Adaption:Motion aftereffect

  17. Where is motion processed?

  18. Higher effects:

  19. Equivalence:Reich and Spat

  20. Conclusion • Evolutionary motion detection is important • Early processing modeled by Reichardt detector or spatio-temporal filters. • Higher processing poorly understood

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