The presentation describes Physically Based Lighting Pipeline of Killzone : Shadow Fall - Playstation 4 launch title. The talk covers studio transition to a new asset creation pipeline, based on physical properties. Moreover it describes light rendering systems used in new 3D engine built from grounds up for upcoming Playstation 4 hardware. A novel real time lighting model, simulating physically accurate Area Lights, will be introduced, as well as hybrid - ray-traced / image based reflection system. We believe that physically based rendering is a viable way to optimize asset creation pipeline efficiency and quality. It also enables the rendering quality to reach a new level that is highly flexible depending on art direction requirements.

3. Lighting
Killzone : Shadow Fall
Michal Drobot
Senior Tech Programmer
Guerrilla Games

4. Intro
 Guerrilla Games is SCEE studio based in Amsterdam
 Working on two Playstation 4 titles:
 Killzone: Shadow Fall
 New IP
 Killzone: Shadow Fall is a launch tile
 Annouced during Playstation 4 reveal
 Running on target 1080p 30fps

5. Focus
 Physically Based Lighting
 Physically Based Area Lights
 Rendering Pipeline

6. Motivation
 Killzone 3
 Shipped in 2011
 Matured PS3 technology
 Considered one of generation visual benchmark titles
 Killzone : Shadow Fall
 Next generation launch title
 How does it compare?

13. Generation change

15. Motivation
 Physically Based Lighting
 Easier to achieve hyperrealism / photorealism
 Consistent look in different HDR environments
 Simple material interface for artists
 Easy troubleshooting and extension

16. Theory

17. Light Flux
 Irradiance = integrated light incoming from all directions (diffuse)
 Radiance = light incoming from one direction (specular reflection)
Irradiance (E)
Radiance (L)

18. Courtesy of ILM
Image Based Lighting (IBL)

19. Courtesy of ILM

20. Courtesy of ILM

21. Physically Based Lighting Model
 Physically Based Shading Model
 Responsible for surface response to incoming light depending on various
surface physical properties
 Physically Based Lights
 Responsible for light flux calculation in the scene depending on various lights
with physical properties

22. Physically Based Shading : Real life
examples
 Specular
 Dominant part of visible lighting
 Every material exhibits specular lighting
 Angle dependent
 Material type dependant

23. Real life lighting
Courtesy of John Hable
Diffuse Specular

24. Real life lighting
Courtesy of John Hable
Diffuse Specular

25. Real life lighting
Courtesy of John Hable
Diffuse Specular

26. Real life lighting
Diffuse Specular
+
Courtesy of John Hable
Diffuse Specular

27. BRDF
Diffuse
Specular
Eye

28. Fresnel
‘Rough’
Reflection
Refraction

29. Non metals

30. Metals

31. Roughness
‘Smooth’
‘Rough’

32. Roughness
‘Smooth’

33. Visibility / Self Shadowing

34. Energy Conservative
Non - Energy Conservative

37. Workflow
 3 main parameters
 Albedo (RGB8)
 Roughness (R8)
 Specular Reflectance (RGB8)
 Material response
 Decoupled from Lighting
 Works in any light environment
 Review assets in different IBL
lighting environments

41. Smooth
(1.0)
Rough
(0.0)
Diffuse

42. Material properties
 Measured values for most materials
 Available in physical tables
 Every material can be roughly defined
by those parameters
 We provided them as Photoshop
color swatches
 Base for hand painted textures

43. Use case
 Material
 Old iron plate
 Covered in paint
 Scratches
 Bullet holes
 Rust

44. Simplified Roughness texture
Thin old paint, scratched,
showing off iron underneath
Due weathering effects smoothened
R = High
Pure rust
R = very low
Rusting metal
R = mixed, sparkles of
medium smooth metal
Bullet hole
High temperature smoothens iron
(due to impact energy)
R = very high
Pure old paint
R = medium

45. Simplified Specular Reflectance texture
Thin old paint, scratched,
showing off iron underneath
SR = Low Iron
Pure rust, non metal
SR = Low, non metal
Rusting metal,
SR = Medium, non metal,
Sparkles of Low Iron
Bullet hole exposes pure Iron
SR = Iron
Pure paint
SR = Low, Medium, High non metal,
Depends on paint type
Old paint = Low
New paint = Medium / High

46. Simplified Albedo texture
White thin old paint, scratched,
showing off iron underneath
A = Dark gray (showing off metal)
Pure rust,
A = Rusty in range of old concrete
Bullet hole exposes pure Iron
A = Very dark (metal)
White old paint
A = White in albedo range of concrete
(light gray)

47.  Shadow Fall BRDF
 Based on Cook-Torrance
 Fresnel
 Smith Schlick Visiblity Function
 Normalization based on
Specular Reflectance
 Roughness as Specular
Importance Cone Angle
 Approximate translucency
 Density maps
 Translucency diffusion maps

48. IBL Point Based BRDF

49. IBL Point Based BRDF – factor visualization

50. IBL Ambient BRDF – factor visualization

51. IBL Ambient BRDF

52. IBL Point Based BRDF

53. IBL Ambient BRDF

54.  Big step for the studio
 Artists had to adapt
 Training and workshops
 Production and Quality Win

59. Physically Based Lights

60. Blinn-Phong Point Light

61. Blinn-Phong Point Light

62. Area Lights
 Every light source
 Size
 Shape
 Intensity
 Art
 Photography
 Light Direction

64. Spherical Light

65. Disc Light

66. Rectangular Light

67. Texture Rectangular Light

68. Area Size and Intensity

74. α
α
pC0
pC1
d0
d1
pC0 > pC1, due to d0 > d1
Result : pC0 blurier than pC1

78. Irradiance Integral
 DA : I(p,n) = Integrate(A) [L * cos(fi) * cos(fo) * dA / d^2]
 dA – differential area of the light
 L – luminance of light
 A – Area of the light
n
p’
p
d n’
fi
fo

79. n
p
Y
X
3D – Word Space
X , Y – set the light frame
Radiance Integral

80. 2D – projected
on light frame
X
Y

81. 2D – projected
on light frame
X
Y
Area of integration

82. X
Y
PDF to integrate
Over Area

84. IES Light Profiles

85. IES Light Profiles

86. IES Light Profiles

88. Lighting Pipeline Overview

89. IBL Reflection System
 3 Tier Reflection Raytrace system
 Realtime Glossy Reflections
 Localized Cubemaps
 Skybox

99. Localized Cubemaps

102.  Picture of pretty cubemap in cross with mips

103.  Picture of pretty cubemap in cross with mips

106. IBL Render Pass
Breakdown

107. Render Pass Breakdown
Baked Lightmaps Diffuse + Dynamic Lights

108. Ambient BRDF

109. Cubemaps

110. Lightmap Diffuse + Dynamic Lights + Ambient BRDF * Cubemaps

111. Real Time Glossy Reflections

112. Real Time Glossy Reflections : Mask

113. Final composite of IBL based lighting

114. Render Pass Breakdown

116. Takeaway
 Physically Based Lighting
 Higher quality
 Faster asset production
 Asset reuse in different environments
 Physical Area Lights
 Time to say goodbye to point lights
 Easier workflow
 High quality results
 Real Time Reflections
 Important visual clue

117. We are hiring!
www.guerrilla-games.com/jobs

118. References
 Real Time Rendering 3rd Edition by Tomas Akenine-Moller, Eric
Haines, Naty Hoffman
 Physically Based Rendering, Second Edition: From Theory To
Implementation by Matt Pharr
 Industrial Light & Magic
 John Hable blog - http://filmicgames.com/