These slides are a portion of the lecture on "Real-Time Rendering of Physically Based Optical Effects in Theory and Practice" at Siggraph 2015. The whole course is available on the tri-Ace web site. All of the Silicon Studio slides are available from our web site. Silicon Studio: http://www.siliconstudio.co.jp/rd/presentations/ tri-Ace: http://research.tri-ace.com/s2015.html このスライドはSIGGRAPH2015のCourse「Real-Time Rendering of Physically Based Optical Effects in Theory and Practice」の講演資料の一部です。Course全体のスライドはトライエースのWebサイトに掲載されています。元のスライドデータは、シリコンスタジオまたはトライエースのWebサイトからダウンロードできます。 シリコンスタジオ：http://www.siliconstudio.co.jp/rd/presentations/ トライエース：http://research.tri-ace.com/s2015.html

1. Making Your Bokeh Fascinating
Real-time Rendering of Physically Based Optical Effect in Theory and Practice
SIGGRAPH 2015 Course
Masaki Kawase
Silicon Studio, Corp.
masa@siliconstudio.co.jp

2. Introduction
• Basic idea and theory [Kawase08]
– Only circular aperture
• Practical implementation and optimization [Kawase12]
– Any kind of aperture shapes
2

3. Contents
• Creating the Pencil Map
• Creating the Bundle-of-Light-Ray Map (Pencil Map)
– “Bundle of Light Rays” or “Pencil Rays”
(referred to as “Pencil” here onwards)
• Application to Arbitrary Aperture Shapes
• Scattering or Gathering?
• Results
• Conclusion
3

4. Creating the Pencil Map

5. Creating the Pencil Map
• Precompute light paths from the aberration diagram
– Takes spherical and axial chromatic aberrations into account
Light paths make up
pencil map
(small number of rays)
Longitudinal aberration
diagram
Pencil map
Amount of aberration
Incidentheight
5

6. Circular Bokeh Rendering
• V coordinate represents the distance from the optical axis
– Mapping each slice to a circle produces a circular ‘bokeh’
Pencil map
Circular bokeh
U: Distance from lens
V:Distancefrom
opticalaxis
6

7. Discretized Result…
7
• Chromatic aberration is an issue
• Three wavelengths (R/G/B) are insufficient to represent the
dispersion

8. Increasing Wavelength Samplings
• Calculate the map with more wavelengths
• Convert into the RGB space
8

9. 3-Wavelength Samplings
9

10. Sufficient Wavelength Samplings
10

11. Bokeh with Spherical and Chromatic Aberration
• Imperfect focus
• Front bokeh with red sharp edge
• Back bokeh with blue soft edge
11
Zoomed-in view around the focal point

12. Comparison with photographs
Captured in real photographs
Generated from pencil map
12

13. Creating the Pencil Map of Doublet
13
• Calculate the map with the longitudinal aberration diagram
• Using actual lens parameters (if they exist)
– Only ray paths of each wavelength are required
Light paths make up
pencil map
Longitudinal aberration
diagram
Pencil map

14. Pencil Map of Doublet
Pencil maps and bokeh
Zoomed-in view around the focal point
14

15. Comparison with photographs
15
• Typical correction
– Front bokeh has soft purple edge and the center is darker
– Back bokeh has sharp green edge and the center is brighter
Front bokeh in photographs Back bokeh in photographs
Front and back Bokeh with Pencil map

16. Different Type of Doublet
• Residual chromatic aberration is more visible than
residual spherical aberration
Light paths make up
pencil map
Longitudinal aberration
diagram
Pencil map
16

17. Pencil Map of Doublet (Different Type)
Zoomed-in view around the focal point
Pencil maps and bokeh
17

18. Pencil Map of Doublet (Previous Type)
Pencil maps and bokeh
Zoomed-in view around the focal point
18

19. Comparison with photographs
Front bokeh in photographs Back bokeh in photographs
Front and back Bokeh with Pencil map
19

20. Optimization of Pencil Map
• Wasteful parts in the texture
– Sparse, many texels are empty
– There is not enough precision around the more important
‘focusing’ texels
Wasteful pencil map
20

21. Optimization of Pencil Map (cont’d)
• Normalizing height of bundle at every distance(u-axis)
by the maximum height(bokeh size)
• Less empty texels, and great improvement in precision
around focusing texels
Wasteful pencil map Normalized pencil map
21

22. Spherical lens (with no corrections)
Aspherical lens (chromatic aberration is not corrected)
Achromatic doublet lens
22

23. Achromatic doublet lens (different type)
Apochromatic (APO) lens
Perfect lens (does not actually exist)
23

24. Application to Arbitrary Aperture Shapes

25. Various Aperture Shapes
• Aperture shape is an important artistic factor
– Typically 5~9 diaphragm blades
– Changes from rounded to n-gon
• How to map pencil onto the polygonal aperture shape?
– 3D Textures?
• Too large, not practical
?
Pencil map
Aperture shape
25

26. Indirect Reference of Pencil Map
• Precompute an LUT texture that stores V coordinates of
pencil map
LUT texture
0
1
0
0
0
0
0
0
0
0
0
0
0
0
1
V
Vertical slice
26

27. Indirect Reference of Pencil Map (cont’d)
• Sample pencil map indirectly
at run-time
Pencil map
0
1
V
Look up
Sampling
LUT 27

28. Indirect Reference of Pencil Map (cont’d)
• LUT determines the aperture shape
– Independent of pencil map
– Can reproduce curved shapes of a diaphragm blade
• Prepare a set of LUTs for various diaphragm conditions
– Other shapes such as stars, hearts, … can be used
28

29. Various LUTs
• For the number of diaphragm blades and opening levels
• Smooth deformation is possible by interpolating between two adjacent LUTs
4 blades
5 blades
6 blades
7 blades
Fully opened ClosedClosing
29

30. Silhouette LUTs for debug
Fully opened
4 blades
5 blades
6 blades
7 blades
ClosedClosing
30

31. Scattering or Gathering?

32. Both can be Implemented
• Better quality by scattering
– Heavy processing load
• Hybrid method is recommended
– Both scattering and gathering
32

33. Hybrid Method
• To determine which pixels will be scattered or gathered,
use:
– The CoC size
– Difference in luminance between neighboring pixels
Original Result (green: gathering pixels)
33

34. 34
Gathering

35. 35
Hybrid of Scattering and Gathering

36. Optimization
• Use a half resolution buffer for scattering
– Scattering process can be 16x faster
• Split the process into several passes with
hierarchical resolution buffers
– Use lower resolution for larger bokeh
– The process at the 1/4 x 1/4 resolution can be 256x faster
• Scatter a pixel every 2x2 pixels
for relatively larger bokeh in each resolution
– Pixels that have an especially heavy processing load will be 4x faster
36

37. Results

38. Back bokeh with cyan fringes
Front bokeh with red/purple fringes
Bokeh Simulation in Real Time

39. Diaphragm Simulation
5-blade Aperture

40. Diaphragm Simulation
6-blade Aperture

41. Diaphragm Simulation
7-blade Aperture

42. Diaphragm Simulation
8-blade Aperture

43. Curved Diaphragm and Optical Vignetting
• Opening / Closing
– Deformation
• Circular aperture
• Polygonal aperture
– Rotation
– Optical Vignetting
• Cat’s Eye Effect
43

44. 5-blade Circular Aperture (with Optical Vignetting)
f/1.4 (Fully Opened)

45. 5-blade Circular Aperture (with Optical Vignetting)
f/2 (1 Stop Closed)

46. 5-blade Circular Aperture (with Less Optical Vignetting)
f/2.8 (2 Stops Closed)

47. 5-blade Circular Aperture (with No Optical Vignetting)
f/5.6 (4 Stops Closed)

48. 5-blade Circular Aperture (with Fake Diffraction Spikes)
f/11 (6 Stops Closed)

49. Various Aberrations and Corrections
• Correction of SA and axial CA mostly affect bokeh
Focus plane
Back bokeh
Front bokeh
Differences between front and back bokeh
49

50. 50
Spherical Lens (with No Corrections)

51. 51
Aspherical Lens (with Chromatic Aberrations)
Correction of Spherical Aberration

52. 52
Achromatic Lens
Corrected for Red and Blue Wavelengths

53. 53
Achromatic Lens (Different Type)
Corrected for Red and Blue Wavelengths

54. 54
APO (Apochromatic) Lens
Corrected for 3 Wavelengths (More Expensive Lens)

55. 55
Almost Perfect Lens
Without any Spherical and Longitudinal Chromatic Aberrations

56. 56
STF (Smooth Transition Focus) Lens
Soft Edged Bokeh by Apodization Optical Element
Radial gradient ND filter

57. Residual Aberration Visibility
Out of focus: Large
Aberrations: Less visible
Out of focus: Small
Aberrations: Strongly Visible

58. Residual Aberration Visibility
Out of focus: Large
Aberrations: Less visible
Out of focus: Small
Aberrations: Strongly Visible
Out of focus: Large
Aberrations: Less visible
Out of focus: Small
Aberrations: Strongly Visible

59. Comparison with Photographs (Achromat)
Real photographs with achromatic lensReal-time simulation results
59

60. Comparison with Photographs (APO)
Real photographs with apochromatic lensReal-time simulation results
60

61. Conclusion

62. Conclusion
• Reproduce photorealistic bokeh with pencil map and LUT
– Pencil map defines bokeh characteristics
– LUT defines bokeh shapes
• Optimization
– Various options available
– Combinations can be used to improve performance
62

63. References
• [Kawase08] Kawase, M. “Bokeh Expressions Based on Optics.” Computer Entertainment Developers
Conference, 2008.
• [Kawase12] Kawase, M. “Practical Implementation of Cinematic Lens Effects.” Computer
Entertainment Developers Conference, 2012.
• Kawase, M. “Reduce Artifacts Generated by Mipmapped Buffers.” Computer Entertainment Developers
Conference, 2009.
• Trávník, J. “On Bokeh.” Jakub Trávník's resources. http://jtra.cz/stuff/essays/bokeh/index.html
• 安藤幸司 『光と光の記録「レンズ編」』 AnfoWorld http://www.anfoworld.com/LensMF.html
• 吉田正太郎（1997）『カメラマンのための写真レンズの科学』地人書館.
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