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“A bit more Deferred” - CryEngine 3
Triangle Game Conference 2009
Martin Mittring – Lead Graphics Programmer
Crytek
• Main office:
Germany Frankfurt
• More studios:
Kiev, Budapest, Sofia, Nottingham, Seoul
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English as company language
30+ nationalities
CryEngine 1: PC only (Far Cry …)
CryEngine 2: PC only (Crysis …)
CryEngine 3: PC, XBox360, PS3
(announced GDC09)
• 32/64 Bit, WinXP/Vista, DX9/10, Multi CPU/GPU
• WYSIWYP
• ResourceCompiler
Source asset -> Platform specific
• Direct Light: Shadow mapping
• Indirect Light (AO): SSAO / RAM / ...
• No precomputed lighting
Production time saver, Memory, Consistency, Dynamic content
• Übershaders
[Mittring07]
Goals after CryEngine 2
• PS3 / XBox360
GPU, CPU, memory
• Improve streaming
• Improve multithreading
• Improve lighting
• More predictable performance
• Tackle the shader combination issue
What is the shader
combination 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
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
=> Decouples geometric complexity from lighting and shading
=> Helps on shader combination issue and predictable performance
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
Deferred in CryEngine 2
• Main use:
Deferred shadows, Per pixel fog
• Additionally:
Soft Z clipped Particles, Motion Blur, Beach/Ocean, EdgeAA,
Sun Rays, SSAO, Fake lights, 2.5D TerrainAO
SSAO
ShadowMask
Deferred Lighting in CryEngine 3
Z (native)
Normal
Specular Power
• Passes:
1) Forward GBuffer generation
2) Deferred light accumulation into texture (Phong)
3) Forward shading with light accumulation texture => 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]
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 diffuse*strength)
The following pictures show lighting with two differently coloured lights:
6 channels (correct)
4 channels (fast)
Light accumulation texture in IBL
The following pictures show lighting with Diffuse and Specular Cubemaps:
• Diffuse RGB
Specular RGB
High Quality
(left)
• Diffuse RGB
Specular Strength
Fast Rendering
(right)
• Difference often
neglectable (depends
on environment)
Storing normals in the GBuffer
• XYZ world space
8 bit: problematic with extreme reflections/specular
10 bit: good, but what about specular power and PS3
• Solving Quantization Artefacts
Detail Normalmaps, Noise, Dither
• XY view space (Z reconstruct)
8/10/16 bit, negate Z bit (perspective and normal mapping)
=> Problematic
[Lee09] [Lob09]
Alternative: VS Normal in 2 scalars
-1..1 => -1..1
Normal to GBufffer:
G=normalize(N.xy)*sqrt(N.z*0.5+0.5)
GBuffer to Normal:
N.z=length2(G.xy)*2-1
N.xy=normalize(G.xy)*sqrt(1-N.z*N.z)
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more precision where it matters (bright part)
framebuffer blending friendly
no z reconstruction issues
wasted area
more ALU than WS
=> still, WS normals are faster
Improved SSAO (with normals)
Light rasterization in
2D (Rectangle) or 3D (Convex Object)
• 2D
+ cheap WS position reconstruction (Interpolator+MAD)
+ 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)
Deferred Light Types 1/3:
• Directional light
optional with cloud shadows, multiple shadowmaps
• Point/Projector lights
optional with projector texture
• Procedural Caustics
(before this was multi-pass, one drawcall for each object under water
including terrain)
• Interleaved Shadowmap lookups
no extra memory
less bandwidth needed
no limits on shadow mask channel count
Deferred Light Types 2/3:
Image Based Lighting (IBL)
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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 condition
by 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
Ambient without SSAO
with hemispherical lighting
Bright ambient
SSAO
Grey ambient (hemispherical)
Shadow casting light source
SSAO
Black ambient
Shadow casting light source
SSAO
IBL ambient (Specular and Diffuse)
Shadow casting light source
SSAO
* brightened up for better display
IBL ambient (Specular and Diffuse)
SSAO
Deferred Light Types 3/3:
Real-time Dynamic Global Illumination
• Details will be presented at upcoming
Siggraph 2009 by Anton Kaplanyan
who 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
Global Illumination off
black ambient
(to emphasize where GI
affects the image)
color bleeding
bump without light
fully dynamic
real-time
Global Illumination on
* brightened up for better display
Global Illumination
Something missing?
Transparency
=> falling back to well known techniques:
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–
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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
=> Nasty but possible
– EdgeAA, …
... we work on it
References
•
[Mittring07] “Finding Next Gen CryEngine2“
Siggraph 2007, Martin Mittring
http://ati.amd.com/developer/gdc/2007/mittring-finding_nextgen_cryengine2(siggraph07).pdf
•
[Engel08] “The Light Pre-Pass Renderer“
ShaderX7, Wolfgang Engel
http://diaryofagraphicsprogrammer.blogspot.com/2008/03/light-pre-pass-renderer.html
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[Lee09a] “Prelighting“
Mark Lee
http://www.insomniacgames.com/tech/articles/0209/files/prelighting.pdf
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[Lee09b] “Pre-lighting in Resistance 2“
GDC 2009, Mark Lee
http://www.gdconf.com/conference/Tutorial%20Handouts/200_insomniac/gdc09_insomniac_prelighting.pdf
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[Geldreich09] ”Deferred Lighting and Shading”
GDC 2009, Rich Geldreich, Matt Pritchard, John Brooks
http://archive.gdconf.com/gdc_2004/pritchard_matt.ppt
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[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
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[Lob09] S.T.A.L.K.E.R : Clear Sky – a showcase for Direct3D 10.0/1
GDC 2009, Igor A. Lobanchikov, Holger Gruen
http://www.gdconf.com/conference/Tutorial%20Handouts/100_Advanced%20Visual%20Effects%20with%20Direct3D/100_Handout%202.pdf
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[Valient07] “Deferred Rendering in Killzone 2“
Develop Conference 2007, Michal Valient
http://www.guerrilla-games.com/publications/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