【Unite Tokyo 2019】Unityでレイトレーシングしよう！レイトレーシング実装と最適化の解説

Real-Time Ray Tracing Paulo Silva Developer Technology Engineer, NVIDIA

Announcements • Target Audience: • • Level: • • • Engineers & Technical Artists Beginner (no programming) Intermediate (some programming) Warning: • This is Beta software and is still changing • Slides will be available • Session recording will also be available 3

Outline • History Of Ray-Tracing • Rasterization vs Ray-Tracing • Basic Example • Scriptable Pipelines & DXR Details • Performance Advice • More Resources 4

History of Ray-Tracing 5

What is Ray-Tracing? • Rendering method • Simulates light path • Most modern movies use it for SFX • Photo-realistic rendering • Car & Architecture visualization 6 Rendered in unity using real-time ray tracing

History • Whitted 1980 • Cook 1984 • Kajiya 1986 • Shiny • Fuzzy • Path Tracing • Reflections • Motion Blur • Rendering Equation • Refractions • Soft Shadows • Diffuse Interreflections • Shadows • Caustics 7

History • Whitted 1980 • Cook 1984 • 8 Kajiya 1986

Rasterization vs Ray-Tracing 9

Rasterization: Very Simplified Vertex Shader Rasterizer 10 Pixel Shader

Ray-Tracing: Very Simplified Trace Rays Intersection Test 11 Shade & Trace

Rasterization vs Ray-Tracing: Key Ideas Rasterizer Ray Tracing Question Which pixel □ does triangle △ cover? Which triangles △ does pixel □ see? Operation Pixel □ in triangle △ Ray → triangle △ intersection Streaming Triangles △ Rays → Inefficiency Overdraw △ Many → collisions Speedups Bounding volume hierarchy BVH (AABBs) (Hierarchical) Z-buffering 12

Rasterization: Hacks SSAO Shadow Maps SSR 13

Rasterization vs Ray-Tracing: AO SSAO Ray-Tracing AO 14

Rasterization vs Ray-Tracing: Shadows Shadow Maps (No baked light maps) Ray-Tracing Shadows 15

Rasterization vs Ray-Tracing: Reflections #1 SSR Ray-Tracing Reflections 16

Rasterization vs Ray-Tracing: Reflections #2 SSR Ray-Tracing Reflections 17

Basic Example 18

Basic Example • No programming needed • Setup needed to get started • Shows off the main features • • • • • Reflections Shadows Ambient Occlusion Global Illumination Compare to Rasterization Cornell Box 19

System Requirements • RTX GPU for complex Ray Tracing Effects* • Windows 10 v1809 • Unity 2019.3b1 20

Setup • In Player settings set: • • • DirectX12 (Experimental) REALTIME_RAYTRACING_SUPPORT ENABLE_RAYTRACING 21

Basic Demo Scene • Let’s create a Cornell Box 22

Basic Demo: Add Ray Tracing • Add the Raytracing Environment 23

Basic Demo: Reflections After Before 24

Basic Demo – Shadows After Before 25

Basic Demo – Indirect Illumination After Before 26

Basic Demo: Raster vs Ray Tracing Ray-Tracing Raster (no baked lights) 27

Scriptable Pipelines & DXR Details 28

Scriptable Pipelines & DXR Details Required for next section: • DXR shader types • Acceleration structures What is DXR? • DXR = D3D12 ray tracing • HDRP uses Scriptable Pipelines • These use DXR ray tracing DXR shaders in HDRP 29

DXR Shaders • Ray Generation • • Closest-hit • • e.g.: sample skybox Any-hit • • e.g.: calculate color Miss shader • • defines how rays start run once per hit for transparency Intersection • Intersect arbitrary shapes DXR Shader Graph 30

DXR Acceleration Structures Acceleration Structure Bounding Boxes are Axis Aligned (AABB) 34

Performance Advice 35

Performance Advice - Reflections Smooth – Coherent Rays Rough – Rays Diverge • • Smooth reflective surfaces are cheaper than rough surfaces Keep shaders simple when using rough surfaces 36

Performance Advice -Transparency Opaque – No Any-Hit call Transparent – many Any-Hits calls • • Keep Any-Hit shaders simple When possible make objects opaque (Use LOD) 37

Performance Advice – Acceleration Structures Static Object • Dynamic Rigid Body Correctly tag objects as static, dynamic, animated 38 Animated Character

Performance Advice – Acceleration Structures AS AS AS AS One Object ☺ Separate Objects ☹ • Group geometry together when possible 39

Performance Advice Performance Quality Ray Count Ray Length Denoiser Quality Small Transparent Objects 40

More Resources 43

More Resources • Ray-Tracing Gems (free pdf): http://www.realtimerendering.com/raytracinggems/ • SIGGRAPH 2018 DXR Tutorial: http://intro-to-dxr.cwyman.org/ • Gameworks Ray-Tracing: https://developer.nvidia.com/gameworks-ray-tracing • DXR Specification: https://microsoft.github.io/DirectX-Specs/d3d/Raytracing.html • Unity HDRP DXR Build: get 2019.3b1 from unity hub, or download the following version https://github.com/Unity-Technologies/Unity-Experimental-DXR 44

• http://www.realtimerendering.com/raytracinggems/
• http://intro-to-dxr.cwyman.org/
• https://developer.nvidia.com/gameworks-ray-tracing
• https://microsoft.github.io/DirectX-Specs/d3d/Raytracing.html
• https://github.com/Unity-Technologies/Unity-Experimental-DXR

Please try real-time ray tracing and make something amazing! Thank You 45