1. ShaderX7
8.1 Cross-Platform Rendering Thread
: Design and Implementation
shader study http://cafe.naver.com/shader
ohyecloudy http://ohyecloudy.com
2011.01.17

2. • Motivation
• Overview
• Implementation
• Going Further
• Conclusion

3. • 프로세서 코어 퍼포먼스는 향상
– 하지만 CPU bottleneck 해결은 여전히 문제
• GPU 퍼포먼스는 향상
– 플랫폼 그래픽스 API 호출에 여전히 CPU 파워가
필요.

4. • 렌더링 작업을 decoupling.
– CPU bottleneck 최소화
– GPU 퍼포먼스 낭비를 최소화

5. • Motivation
• Overview
• Implementation
• Going Further
• Conclusion

6. Threading Design
Game
Thread Game
Client
DRIVER
Command
Buffer
Server
Server API (OpenGL, DirectX, ...)
Thread Server-Client
Model

7. Abstraction Design
• platform-specific 구현을 숨김
• rendering pipeline stage 전체를 커버

8. Command Objects
• client side
– 실제 동작은 없음. request 역할.
• server side
1. server-API 를 사용하는 오브젝트로 빌드.
2. command가 예약된 만큼 실행
• 재생성 필요 없음

9. Command Buffer
• client와 server를 연결
– client, server는 각 쓰레드가 돌고 있음.
• multi-threading issue가 발생하는 곳

10. State Machine
• state cache
– rendering pipeline 추상화
• binding
– render target state
– camera state
– light state
– material state
– transform state
– ...

11. Macro State Objects
• one-to-many 관계
– client state와 server state
• client state
– RenderTarget
• server state
– clear information and operation (color, flags, ...)
– render buffer characteristics (size, ...)
– post-effects parameters and execution (blur,...)

12. Driver Execution Process
Game Client State Command Server Platform
Engine Cache Buffer Graphics API
DirectX
Bind Queue
State OpenGL
Swap
PS3
Build & XDK
Dispatch
Queue ...
Command
Queue

13. • Motivation
• Overview
• Implementation
• Going Further
• Conclusion

14. Driver Objects Pattern
<<interface>> <<interface>>
Client Command Server Command
<<interface>>
Command +Queue() +Build = 0()
+Dispatch = 0()
+Queue()
+Build = 0()
+Dispatch = 0()
Client Draw Command Server Draw Command
<<interface>>
Client Draw Command
+SetColor()
<<interface>>
Command Data
Server Draw Command
+Build()
+Dispatch()
Draw Command Data
+SetColor()
A B

15. Driver Objects Pattern
• one-to-one X
<<interface>> <<interface>>
• client code
Client Command Server Command
+Queue() +Build = 0()
+Dispatch = 0() • server code
Client Draw Command Server Draw Command
• lifetime이 client, server
<<interface>>
Command Data
분리
Draw Command Data
+SetColor()

16. Three Command Objects
• client command
– queuing
– lifetime management
• command data
– server code 실행에 인자로 사용
• server command
– platform graphics API-specific code

17. synchronization : command buffer
• double buffering
– client가 하나를 채우는 동안
– server는 하나를 실행하고 비움
• synchronization points
– client frame end
– server frame end

18. Thread Safety :
Command Data Sharing Policy
• command data에 접근
– client, server 둘 다
– 퍼포먼스가 중요
– thread safe를 보장하지 않음
• 수정이 필요하면 재생성
• refcount > 0
– 수정하려면 재생성.

19. Thread Safety :
Command Locking Strategy
// RAII Object
sxCScopeLocker oLock(rCommand);
sxCCommandData& rCommandData =
oLock.GetData();
if (TestSomething())
{
return;
}

20. • Motivation
• Overview
• Implementation
• Going Further
• Conclusion

21. Optimization : Triple Buffering
Client Buffer 2 Buffer 1 Buffer 3 Buffer 1
Server Buffer 3 Buffer 2 Buffer 3

22. Command Buffer Serialization-Based
• 전체 rendering command sequence 저장
• debugging에 유용하게 사용할 수 있다.

23. • Motivation
• Overview
• Implementation
• Going Further
• Conclusion

24. • wait-free rendering thread 구현
• one-to-many 관계
– client, server state
• client-server 접근으로 decoupling
– platform 종속적인 코드는 server에만