Umbra Software's Principal programmer Ari Silvennoinen discusses "Occlusion Culling in Alan Wake" as Remedy's critically-acclaimed thriller utilized Umbra's occlusion culling solution. We'd like to thank the fine gentlemen at Remedy for their help in putting together this presentation.

2. Occlusion Culling in Alan Wake Ari Silvennoinen

3. Rendering Challenges in Alan Wake

5. Large outdoor world

6. Dynamic objects

7. Local shadow rendering

8. Global shadow rendering

9. Umbra internals

10. Techniques and ideas used to tackle the rendering challenges

11. Umbra is the visibility middleware used in Alan Wake

13. Efficient data handling

15. Out-of-core objects should be cheap

16. Efficient initial construction

19. Premultiplied OBB representation for objects

20. 4x3 matrix for mapping the unit cube to world space OBB

21. Lazy update mechanism based on camera frustum

22. Mark nodes as dirty, update when actually traversed

23. Automatic amortized updates

24. Split plane optimization to improve spatial subdivision

26. Avoiding latency by interleaving work

27. Umbra does hierarchy traversal and database update tasks to prevent CPU stalling

28. Works well in practice, however 100% utilization impossible due to GPU starvation

29. Avoiding latency by delayed reads

30. Artifacts!

32. Screen space error bounds for artifacts

33. Adaptive query bounds

34. Some queries can be guaranteed to be ready with high probability

35. Keep the query count low

36. Queries are cheap but not free

37. Intelligent batching

40. Temporal bounding volumes

41. Linear prediction with conservative dynamics model

42. Stable and fast

43. Temporal bounds are AABBs

44. Has even been used with bullets driven by physics 

45. Take advantage of lazy and amortized updates

46. Keeps hierarchy balanced during movement

49. Spheres and frustums

50. Aggressive culling

51. Distance culling

52. Test every frame

53. No batching

55. Shadow map generation

56. Shadow map sampling + filtering

57. Lot of objects + cascaded shadows = high shadow map generation cost

59. Observation II Cull objects in which do not cast a visible shadow

61. Test each cascade for visibility

62. Check if the cascade contains any visible objects

63. Can potentially skip shadow map generation

64. Compute light space scissor rectangle for each cascade

65. Early geometry culling

66. These ideas generalize

68. Cascaded Shadow Maps

69. Cascaded Shadow Maps

70. Cascaded Shadow Maps Small scissor Empty cascade

72. Visibility-aware algorithms

73. Shadow caster culling

74. Streaming?

75. Simulation and AI?

76. Rethink visibility and spatial connectivity

78. Petri Häkkinen

79. Markus Mäki

80. Olli Tervo

81. TuukkaTaipalvesi

82. Colleagues at Umbra Software

83. TimoAila