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RAYS (Render As You See)

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... but with corneal topography 3 Major Limitations computation time small light sources artifacts from the model color image with depth values fixation ... – PowerPoint PPT presentation

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Title: RAYS (Render As You See)


1
RAYS (Render As You See)
  • Vision-Realistic Rendering Using Hartmann-Shack
    Wavefront Aberrations

Brian A. Barsky Daniel D. Garcia Stanley A. Klein
Woojin M. Yu Billy P. Chen Sarang S. Dalal
2
Motivation
  • CWhatUC
  • ray tracing approach similar to Kolb, but with
    corneal topography
  • 3 Major Limitations
  • computation time
  • small light sources
  • artifacts from the model

3
The Algorithm (our goal)
  • color image with depth values
  • fixation point and wavefront data
  • generate an image with depth of field and visual
    artifacts consistent with the wavefront

4
Hartmann-Shack Device
5
Hartmann-Shack Device
6
Hartmann-Shack Device
7
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8
Resampling Hartmann-Shack wavefront data
  • encodes gradient/slope of wavefront
  • however, sampling is very sparse!
  • Solution fit a Zernike polynomial to these
    samples
  • resample at higher rate

9
Point Spread Function
  • 2D Retinal energy histogram
  • PSF as a blur filter and subsequent convolution
    with image

10
Object-Space Point Spread Function (OSPSF)
  • analog to the traditional PSF used for
    wavefronts
  • image-space PSF vs. object-space OSPSF
  • array of OSPSFs at each depth plane
  • OSPSF as a generalization of PSF
  • lens to pick fixation point
  • at each depth plane, a tuned diverging lens
    converts a wavefront converging at that depth to
    a plane wave

11
Depth Planes
  • A person with 20/20 vision can perceive a
    subtended angle of one minute
  • ? p?D
  • Assuming a typical pupil diameter of 2.4mm
  • ?D 0.12 diopters
  • We use ?D 0.25 diopters, but the maximum error
    is half the chosen precision
  • Consider a point 1.6 meters away from the lens
  • optometrists typically use 0.25 diopter
    increments for corrective lenses

12
Depth Planes
  • The range of sharp human vision is 10cm to
    infinity
  • At 0.25 diopter increments, we use 41 depth
    planes spaced from 0D (infinitely far) to 40D (10
    cm)
  • Depth planes are placed densely closer to the
    observer, and more sparsely as it approaches
    infinity

13
Rendering Image
  • PRMan
  • RGBZ values

14
Stratification
  • image pixels are separated according to depth
    values into depth strata
  • continuous depth values are quantized into
    discrete values

15
Convolution and Accumulation
  • OSPSFs are convolved with each appropriate
    depth strata
  • Blurred images corresponding depth planes are
    accumulated together

16
Example Images
Cubes
Road to Pt. RAYS
17
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18
Conclusion
  • Vision-realistic Rendering
  • Render As You See (RAYS)
  • Example images
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