Learn how to render beautiful images like Pixar and Disney using a simple algorithm called path tracing. In this talk, we'll trace the paths of billions of photons with Go on commodity hardware. Together, we'll explore concurrency, the behavior of light, and the future of computer graphics.

1. @hunterloftis
Painting with Light
Scenic City Summit 2018

2. @hunterloftis
1940s: The Manhattan Project

3. @hunterloftis
"Monte Carlo Integration"

4. @hunterloftis
1986: Kajiya's rendering equation

5. @hunterloftis
1986: Kajiya's rendering equation
$44,000,000 / GFLOPS

6. @hunterloftis
1995: Toy Story

7. @hunterloftis
“There are more PhDs working on
this film than any other in movie
history.”
- Steve Jobs, Pixar, 1995

8. @hunterloftis
“There are more PhDs working on
this film than any other in movie
history.”
- Steve Jobs, Pixar, 1995
$46,000 / GFLOPS

9. @hunterloftis
-$30,000,000

10. @hunterloftis
-$30,000,000
+$364,545,516

11. @hunterloftis
2006: Monster House

12. @hunterloftis
2006: Monster House
$57 / GFLOPS

13. @hunterloftis
2014: Big Hero 6

14. @hunterloftis
2014: Big Hero 6
$0.13 / GFLOPS

15. @hunterloftis

16. @hunterloftis
4 render farms

17. @hunterloftis
4 render farms
4,600 servers

18. @hunterloftis
4 render farms
4,600 servers
83 hrs / frame

19. @hunterloftis
2016: Deadpool

20. @hunterloftis
2016: Deadpool

21. @hunterloftis
2016: Path-tracing only

22. @hunterloftis
2016: Path-tracing only
$0.08 / GFLOPS

23. @hunterloftis

24. @hunterloftis

25. @hunterloftis

26. @hunterloftis

27. @hunterloftis

28. @hunterloftis

29. @hunterloftis

30. @hunterloftis

31. @hunterloftis

32. @hunterloftis

33. @hunterloftis

34. @hunterloftis

35. @hunterloftis

36. @hunterloftis

37. @hunterloftis

38. @hunterloftis

39. @hunterloftis

40. @hunterloftis
v0.0.1

41. @hunterloftis

42. @hunterloftis
2 obstacles...

43. @hunterloftis

44. @hunterloftis

45. @hunterloftis
JavaScript!

46. @hunterloftis
...time to learn Go!

47. @hunterloftis
$ make moses
(516,526 surfaces!)

48. @hunterloftis
Building a physically-based
path tracer

49. @hunterloftis
Building a physically-based
path tracer
In plain English

50. @hunterloftis
Building a physically-based
path tracer
In plain English
...with as little math as possible

51. @hunterloftis
Building a physically-based
path tracer
In plain English
...with as little math as possible
...and just a touch of physics.

52. @hunterloftis
What is light?

53. @hunterloftis

54. @hunterloftis
origin

55. @hunterloftis
origin
direction

56. @hunterloftis
origin
direction
energy (RGB)

57. @hunterloftis
Origin + Direction + Energy

58. @hunterloftis
What happens when light hits a
surface?

59. @hunterloftis

60. @hunterloftis
Reflection

61. @hunterloftis
Reflection
Refraction

62. @hunterloftis
"conductors"

63. @hunterloftis
"dielectrics"

64. @hunterloftis
transmittance diffusion
Once refracted, light is either transmitted or
diffused

65. @hunterloftis
All incoming light is either...
3. transmitted
1. reflected
2. diffused

66. @hunterloftis
How can we simulate these
three behaviors?
3. transmitted
1. reflected
2. diffused

67. @hunterloftis
BRDFs and BTDFs!
"Bidirectional Reflectance Distribution Function"
"Bidirectional Transmittance Distribution Function"

68. @hunterloftis
BRDFs and BTDFs!
"Bidirectional Reflectance Distribution Function"
"Bidirectional Transmittance Distribution Function"

69. @hunterloftis
A pure function that describes a material

70. @hunterloftis
The physics have been done for us!
Metals
microfacet BRDF
Non-metals
microfacet + Oren-Nayar BRDFs
Transparent materials
microfacet BTDF + Beer's law
...car paint, hair, thin films, clouds, skin...

71. @hunterloftis
But... that's just one random path!

72. @hunterloftis
But... that's just one random path!

73. @hunterloftis
“Monte Carlo integration”

74. @hunterloftis
“Monte Carlo integration”

75. @hunterloftis
“Monte Carlo integration”
Sample a bunch of values randomly.

76. @hunterloftis
“Monte Carlo integration”
Sample a bunch of values randomly.
Add them all up and average them.

77. @hunterloftis
“Monte Carlo integration”
Sample a bunch of values randomly.
Add them all up and average them.
That’s probably close to the real answer.

78. @hunterloftis
Path tracing + Monte Carlo integration
rendered with github.com/hunterloftis/pbr

79. @hunterloftis
Path tracing + Monte Carlo integration
rendered with github.com/hunterloftis/pbr

80. @hunterloftis
Path tracing + Monte Carlo integration
rendered with github.com/hunterloftis/pbr

81. @hunterloftis
15x improvement over JS!
rendered with github.com/hunterloftis/pbr

82. @hunterloftis
Quick Recap

83. +
Light Transport
Algorithms
(path tracing, monte carlo
integration)
Physically-Based
Materials
(BRDF, BSDF, etc)

84. https://github.com/google/filament
+
Light Transport
Algorithms
(path tracing, monte carlo
integration)
Physically-Based
Materials
(BRDF, BSDF, etc)

85. https://github.com/google/filament https://github.com/fogleman/pt
+
Light Transport
Algorithms
(path tracing, monte carlo
integration)
Physically-Based
Materials
(BRDF, BSDF, etc)

86. https://github.com/google/filament https://github.com/fogleman/pt
rendered with github.com/hunterloftis/pbr
+
Light Transport
Algorithms
(path tracing, monte carlo
integration)
Physically-Based
Materials
(BRDF, BSDF, etc)

87. @hunterloftis
How can we make
more interesting images?

88. @hunterloftis
Complex geometry
rendered with github.com/hunterloftis/pbr

89. @hunterloftis
Complex geometry
rendered with github.com/hunterloftis/pbr

90. @hunterloftis
Complex geometry
rendered with github.com/hunterloftis/pbr

91. @hunterloftis
Real materials
rendered with github.com/hunterloftis/pbr

92. @hunterloftis
Real materials
rendered with github.com/hunterloftis/pbr

93. @hunterloftis
Real materials
rendered with github.com/hunterloftis/pbr

94. @hunterloftis
Real materials
rendered with github.com/hunterloftis/pbr

95. @hunterloftis
Image-based lighting
rendered with github.com/hunterloftis/pbr

96. @hunterloftis
Image-based lighting
rendered with github.com/hunterloftis/pbr

97. @hunterloftis
Image-based lighting
rendered with github.com/hunterloftis/pbr

98. @hunterloftis
Image-based lighting
rendered with github.com/hunterloftis/pbr

99. @hunterloftis
The Future
5:20

100. @hunterloftis
2018

101. @hunterloftis
2018

102. @hunterloftis
2018

103. @hunterloftis
2018

104. @hunterloftis
2018

105. @hunterloftis
An exciting, emerging field
Research that hasn't been implemented yet
"Embarrassingly parallel" algorithm
Fun to hack on!

106. @hunterloftis
I would love your help!
roadmap:
distributed concurrency
smoothing groups & normal maps
glTF support
expanding the material library
beautiful example scenes!

107. @hunterloftis
How's Moses doing?

108. @hunterloftis
Thank you!
https://github.com/hunterloftis/pbr
https://www.disneyanimation.com/technology/innovations/hyperion
http://www.cse.chalmers.se/edu/year/2013/course/TDA361/Pathtracing.pdf
http://blog.selfshadow.com/publications/s2015-shading-course/hoffman/s2015_pbs_physics_math_slides.pdf
https://www.cs.cmu.edu/afs/cs/academic/class/15462-f09/www/lec/lec8.pdf
https://www.atomicheritage.org/history/computing-and-manhattan-project
https://graphics.pixar.com/library/PathTracedMovies/paper.pdf
https://www.wired.com/1995/12/toy-story/
https://en.wikipedia.org/wiki/FLOPS#Cost_of_computing
Hunter@Heroku.com