Butterfly E!ect DirectX 11 graphic featuresErland Körner, Technical Artist, Unity Sweden

Apr 12, 2013 Page

Who am I?!• I am Erland Körner

• Unity Stockholm, Sweden

• Graphic Artist on demo-team

• 2 decades AAA background. EA/DICE - Battlefield and Mirrors Edge.

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Apr 12, 2013 Page

Unity DirectX11

Butterfly E!ect

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Apr 12, 2013 Page

Unity DirectX11

Summed up• Realtime shortfilm using Unity.

Research project.

• Unity, Passion Pictures and Nvidia.

• ˜25 CG Artists (0 Unity experience), ˜5 Programmers during 14 weeks production time.

• 40GB Data, 40 scenes, 130 shots. Using Unity CacheServer.

• DirectX 11 and 64bit Editor.

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Apr 12, 2013 Page

Unity DirectX11

Usages in Butterfly e!ect

• DX11 = Collection of Windows multimedia API’s for games. Available in Unity 4.x.

• DirectX 11 broadens visual (GPU) scope and fidelity. Eases e!orts.

• Compute shaders, Tessellation and 3D Textures

• Enabling us to have Physically based, energy conservative shaders on environment, skin and eyes

• ...Hair rendering and tessellation

• ...Full screen Post Processing

• ...Volumetric explosions

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Apr 12, 2013 Page

Unity DirectX11

Compute shader example 1• +1 million particles in Unity

• Fully simulated on the GPU, hardly no pressure on CPU.

• GPU bu!er position and velocity.

• Each particle is a generated billboard.

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Apr 12, 2013 Page

Unity DirectX11

Compute shader example 2• Fluid simulation.

• Works on 3D textures and performs simulation.

• Texture describes the density and velocity.

• To show the result the density 3D texture is raymarched.

• A gradient texture is also sampled to provide di!erent color depending on volume thickness.

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Apr 12, 2013 Page

Unity DirectX11

Physically based shaders• Inspired by Mental Ray

“Architectural” (MIA) shader

• High quality o"ine rendering

• Suitable for hard-surface materials

• Familiar and intuitive to CG / non-game artists.

• THE shader for everything!!!

• Energy conserving - Material follows laws of physics!

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Apr 12, 2013 Page

Unity DirectX11

Skin Rendering• Physically based shading.

• Mimics o"ine SSS rendering tools. Top, epidermis and subdermal skin layers.

• Renders lighting, then blurs, combines, and adds top- and 2 spec layers.

• Back scatter, based on translucency layers. Adds intensities into sublayer. Indirect light from spherical harmonics.

• Catmull-Clark Subdivision, not directly Dx11 tessellation.

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Apr 12, 2013 Page

Unity DirectX11

Hair and Tessellation• System designed to be similar

to o"ine systems.

• Geometry shader. Rendered using DirectX 11 tessellation.

• Hardware hair geometry generation.

• Hair defined by Emitter mesh and Guide hairs in 3d package.

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Apr 12, 2013 Page

Unity DirectX11

Filmic Post-E!ects breakdown• Heavy amounts of Post-

processing in every shot!

• ...Motionblur (Velocity blur)

• ...Depth Of Field and Bokeh shapes

• ...Photographic tonemapping

• ...Bloom (HDR, Specular highlights and sun reflections)

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Apr 12, 2013 Page

Unity DirectX11

Filmic Post-E!ects breakdown• ...Color correction (3D LUT)

• ...RGB channel Noise and grain

• ...Lens distortion

• ..HBAO (Horizon Based Ambient Occlusion)

• Some already added to Unity 4.1...

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Apr 12, 2013 Page

Unity DirectX11

Volumetric Explosions• Fluid simulation expensive and

hard to control.

• Procedural techniques are practical on current-gen hardware.

• Fast render volume renderer.

• Can calculate normal as gradient of distance field, for lighting. Gives AO approximations.

• Detail added by o!set with “pyroclastic” (Perlin) noise. Shade based on displacement amount.

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Apr 12, 2013 Page

Thanks and credits

• Renaldas Zioma, Aras Pranckevičius, Ole Ciliox, Paulius Liekis, Stefan Sandberg at Unity

• Simon Green, Jon Jansen an everyone involved of Nvidia

• Passion Pictures

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More examples

Apr 12, 2013 Page

Unity DirectX11

Opacity Mapping example• Fourier Opacity Mapping, for

rendering self-shadowing e!ects.

• DX11 Tessellation, for acceleration.

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Apr 12, 2013 Page

Signed Distance Field example 1• Similar approach as volumetric

explosions.

• Julia fractal. Distance Fields are surfaces defined mathematically.

• For each pixel touched is raymarched a function that describes the fractal.

• Cubemap and AO sampled with the normal for added detail.

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Apr 12, 2013 Page

Signed Distance Field example 2

• Describes whether camera is on the surface (value 0) or above or below it.

• Morphed by other functions, like the wave (sin and cos).

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Apr 12, 2013 Page

Signed Distance Field example 3• Sample until reaching back of

the volume to figure out thickness.

• Dim surface where the volume is thicker.

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