CMPT 461 Final Project Sunny Tam

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CMPT 461 Final ProjectSunny Tam
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Background and Motivation

• Bokeh Japanese term for anesthetic quality of
  out of focus blur
• Different lens produce different types and shapes
  of blur

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Background and motivation

• PBRT provides basic out of focus blurring
• Circular and uniformly sampled
• Often unrealistic and undesirable
• Camera often produces a light ringing or donut
  effect
• Photographers prefer bokeh with softer edges
• Lack of papers and formulas

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Goals

• To provide the ability to specify the shape and
  the distribution of the out of focus blurring
  effect
• Implement in a easy to use, and readily
  expandable manner

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PBRT depth of field

• In essence a disk sampling problem

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1D Non-uniform distribution

• Along the radius pointed by a given theta

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1D Non-uniform distribution

• Exponential
• -ln(u1)/a
• Gaussian
• µ ssqrt(2)erfinv(2u1 1)
• Triangular
• a sqrt(u1(m-a)(b-a)) if u1 lt m
• b sqrt((1-u1)(b-m)(b-a)) otherwise

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Non-circular disk sampling

• Specify a surface which is a subset of the unit
  disk

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Non-circular disk sampling

• From here any 1D distribution can be mapped along
  the length of h

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Results

• Implemented as part of the perspective camera
  class
• Example of usage
• Detailed instructions on website

Camera "perspective" "float fov" 50 "float
lensradius" 0.15 "float focaldistance" 2
"integer mode" 3 "integer shape" 3 "integer
power" 3
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Results

• Computationally expensive to generate high
  quality images

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Challenges

• Difficult to implement equations for the inverse
  cdf of a gaussian distribution
• Requires error function calculation
• Third party methods
• Triangular disk difficult to sample correctly
• Large difference in length of r
• Sqrt the distribution of angles solves the
  problem conceptually but still appear to be
  imperfect

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Conclusion

• Need to accurately model real life camera
  behavior
• Created a plugin that can readily accept more 1D
  distributions
• Lower order polygons not realistic, but provide
  an artistic option

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References

• http//home.online.no/pjacklam/notes/invnorm/impl
  /natarajan/normsinv.h
• http//en.wikipedia.org/wiki/Aperture
• http//en.wikipedia.org/wiki/Bokeh
• http//portal.acm.org/citation.cfm?id282449coll
  GUIDEdlGUIDECFID4354792CFTOKEN43069400
• http//www.flarg.com/bokeh.html
• Matt Pharr and Greg Humphreys, Physically based
  rendering
• http//fendinadia.com/2007/11/modify-your-bokeh.ht
  ml
• http//www.worldscibooks.com/mathematics/etextbook
  /5720/5720_chap1.pdf