A bit more Deferred CryEngine 3

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A bit more Deferred - CryEngine 3
Triangle Game Conference 2009
Martin Mittring Lead Graphics Programmer
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Crytek

• Main office Germany Frankfurt
• More studios Kiev, Budapest, Sofia,
  Nottingham, Seoul
• English as company language
• 30 nationalities
• CryEngine 1 PC only (Far Cry )
• CryEngine 2 PC only (Crysis )
• CryEngine 3 PC, XBox360, PS3 (announced GDC09)

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• 32/64 Bit, WinXP/Vista, DX9/10, Multi CPU/GPU
• WYSIWYP
• ResourceCompiler Source asset -gt Platform
  specific
• Direct Light Shadow mapping
• Indirect Light (AO) SSAO / RAM / ...
• No precomputed lighting Production time saver,
  Memory, Consistency, Dynamic content
• Übershaders

Mittring07
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Goals after CryEngine 2

• PS3 / XBox360GPU, CPU, memory
• Improve streaming
• Improve multithreading
• Improve lighting
• More predictable performance
• Tackle the shader combination issue

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What is the shadercombination issue?

• Übershader is one shader with many features (e.g.
  0..4 lights, light types, CM reflection, fog,
  detail texture, normalmap, specular texture)
• Compiling all possible permutations is a memory,
  production and performance problem
• Usual solutions
• dynamic branching / separating into multiple
  passes / reducing combinations and accepting less
  functionality and less performance
• Asynchronous shader compiling
• Distributed Job System to compile the shader cache

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Why Deferred Rendering?

• Rendering is a multi-dimensional query View x
  Geometry x Material x Light
• Classic Forward Rendering for each light
  render geometry from scene query with shader
• Classic Deferred Rendering render geometry from
  scene query outputting GBuffer render each light
  from scene query and shade with GBuffer
• gt Decouples geometric complexity from
  lighting and shading gt Helps on shader
  combination issue and predictable performance

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GBuffer in CryEngine 2
Z

• Minimal GBuffer (depth)
• Slower Early Z pass when outputting linear depth
• Formats
• R16
• R16G16
• R32
• Proved to be very useful

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Deferred in CryEngine 2

• Main useDeferred shadows, Per pixel fog
• AdditionallySoft Z clipped Particles, Motion
  Blur, Beach/Ocean, EdgeAA,Sun Rays, SSAO, Fake
  lights, 2.5D TerrainAO

SSAO
ShadowMask
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Deferred Lighting in CryEngine 3
Normal
Specular Power
Z (native)

• Passes
• 1) Forward GBuffer generation
• 2) Deferred light accumulation into texture
  (Phong)
• 3) Forward shading with light accumulation
  texture gt No deferred shading
• Deferred Lighting Multiple light
  primitives are possible even Image Based
  Lighting (IBL) easy to extend
• Compared to Deferred Shading Less bandwidth and
  memory problems (10MB EDRAM XBox360) More
  flexibility on shading (besides Phong)

Geldreich09 aka Light Pre-Pass Renderer
Engel08
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Options for the light accumulation texture
sRGB helps to distribute more details in dark
areas

• 6 channels Diffuse and Specular
• two 7e3 7e3 7e3, A16R16G16B16f or A8R8G8B8
• 4 channels Diffuse and Specular strength
• a single A16R16G16B16f or A8R8G8B8 (specular
  approximated by diffusestrength)
• The following pictures show lighting with two
  differently coloured lights

6 channels (correct)
4 channels (fast)
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Light accumulation texture in IBL

• The following pictures show lighting with Diffuse
  and Specular Cubemaps

• Diffuse RGBSpecular RGBHigh Quality(left)
• Diffuse RGBSpecular StrengthFast
  Rendering(right)
• Difference often neglectable (depends on
  environment)

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Storing normals in the GBuffer

• XYZ world space8 bit problematic with extreme
  reflections/specular10 bit good, but what about
  specular power and PS3
• Solving Quantization ArtefactsDetail Normalmaps,
  Noise, Dither
• XY view space (Z reconstruct)8/10/16 bit, negate
  Z bit (perspective and normal mapping)

gt Problematic
Lee09 Lob09
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Alternative VS Normal in 2 scalars-1..1 gt -1..1

• Normal to GBuffferGnormalize(N.xy)sqrt(N.z0.
  50.5)
• GBuffer to NormalN.zlength2(G.xy)2-1N.xynor
  malize(G.xy)sqrt(1-N.zN.z)
• more precision where it matters (bright part)
• framebuffer blending friendly
• no z reconstruction issues
• wasted area
• more ALU than WS

gt still, WS normals are faster
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Video
Improved SSAO (with normals)
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Light rasterization in2D (Rectangle) or 3D
(Convex Object)

• 2D
• cheap WS position reconstruction
  (InterpolatorMAD)
• Combining multiple lights
• Stencil prepass (if not fullscreen)
• Coarse blocks can be rejected based on z min/max
• 3D
• Z buffer
• tighter bounding object (less pixels to
  process)
• Depth bounds test (only on some HW)

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Deferred Light Types 1/3

• Directional lightoptional with cloud shadows,
  multiple shadowmaps
• Point/Projector lightsoptional with projector
  texture
• Procedural Caustics(before this was multi-pass,
  one drawcall for each object under water
  including terrain)
• Interleaved Shadowmap lookupsno extra
  memoryless bandwidth neededno limits on shadow
  mask channel count

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Deferred Light Types 2/3Image Based Lighting
(IBL)

• Light Probes are the high quality solution for
  distant light
• Cubemaps allow efficient HDR lighting in
  real-time
• Diffuse CM can be computed from specular CM
• Mip adjusted lookup allows different specular
  power values
• Improves shading in ambient lighting conditionby
  adding normal dependent and specular lighting
• Light Probes can be generated at specified level
  positions
• Deferred Lighting allows blending of localized
  Light Probes
• Looks even better with SSAO

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Ambient without SSAOwith hemispherical lighting
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• Bright ambient SSAO

Black ambient Shadow casting light source SSAO
Grey ambient (hemispherical)Shadow casting light
source SSAO
IBL ambient (Specular and Diffuse)Shadow casting
light sourceSSAO
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IBL ambient (Specular and Diffuse) SSAO
brightened up for better display
Video
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Deferred Light Types 3/3Real-time Dynamic
Global Illumination

• Details will be presented at upcomingSiggraph
  2009 by Anton Kaplanyanwho developed that at
  Crytek
• Implemented and fast on XBox360, PS3 and PC
• No precomputation
• Fully dynamic (geometry, materials and lights)
• Unified for static and dynamic objects

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Global Illumination off

• black ambient
• (to emphasize where GI
• affects the image)

color bleeding bump without light fully
dynamic real-time
Global Illumination on
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Global Illumination
brightened up for better display
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Something missing?

• Transparency gt falling back to well known
  techniques
• Per pixel global fog and fog volumes (deferred)
• Back to front sorted alpha transparent objects
• Volume texture clouds, Imposter clouds, Distance
  clouds
• Particle systems avoiding per particle sorting
• Anti-aliasing gt Nasty but possible
• EdgeAA,
• ... we work on it

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References

• Mittring07 Finding Next Gen CryEngine2Siggrap
  h 2007, Martin Mittringhttp//ati.amd.com/develop
  er/gdc/2007/mittring-finding_nextgen_cryengine2(si
  ggraph07).pdf
• Engel08 The Light Pre-Pass RendererShaderX7,
  Wolfgang Engelhttp//diaryofagraphicsprogrammer.b
  logspot.com/2008/03/light-pre-pass-renderer.html
• Lee09a PrelightingMark Leehttp//www.insomni
  acgames.com/tech/articles/0209/files/prelighting.p
  df
• Lee09b Pre-lighting in Resistance 2GDC 2009,
  Mark Leehttp//www.gdconf.com/conference/Tutorial
  20Handouts/200_insomniac/gdc09_insomniac_prelight
  ing.pdf
• Geldreich09 Deferred Lighting and ShadingGDC
  2009, Rich Geldreich, Matt Pritchard, John
  Brookshttp//archive.gdconf.com/gdc_2004/pritchar
  d_matt.ppt
• Shish05 Deferred Shading in S.T.A.L.K.E.R.GPU
  Gems 2, Oles Shishkovtsov http//http.developer.
  nvidia.com/GPUGems2/gpugems2_chapter09.html
• Lob09 S.T.A.L.K.E.R Clear Sky a showcase
  for Direct3D 10.0/1GDC 2009, Igor A.
  Lobanchikov, Holger Gruenhttp//www.gdconf.com/co
  nference/Tutorial20Handouts/100_Advanced20Visual
  20Effects20with20Direct3D/100_Handout202.pdf
• Valient07 Deferred Rendering in Killzone
  2Develop Conference 2007, Michal
  Valienthttp//www.guerrilla-games.com/publication
  s/dr_kz2_rsx_dev07.pdf

Slides should be soon at http//www.crytek.com
/technology/presentations
Special thanks to all the passionate people at
Crytek
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