This document discusses different techniques for rendering global illumination (GI) in 3D scenes. It covers direct lighting, hemisphere lighting, lightmaps, light probes, light propagation volumes, and voxel cone tracing. Voxel cone tracing allows for dynamic lights and objects, indirect shadows, but requires a huge amount of memory. It renders indirect lighting in 37 ms for a scene.

2. Why GI?

3. Why GI?

4. What is GI?
Direct lighting
Indirect lighting
What is GI?

5. What is GI?
Only Direct Lighting
Direct + Indirect

6. What is GI?
ON
OFF

7. What is GI?
●
Direct lighting – sucks
●
Direct + Indirect lighting – cool
What is GI?

8. GI in 99 Lines of C++
8 spp
13 sec
200 spp
5 min
1000 spp
25 min
25k spp
10.3 h
2.4 GHz Intel Core 2 Quad, 1024 x 768, by Kevin Beason

9. GI in 99 Lines of C++
●
Brute force – really heavy

10. Hemisphere Lightning
MotoGP

11. Hemisphere Lightning
Radiosity Map

12. Hemisphere Lightning
●
Fast & simple
●
Too simple
Hemisphere Lighting

13. Lightmaps
Mirror's Edge

14. Lightmaps

15. Lightmaps
●
Only static objects

16. Light Probes
Killzone 2

17. Light Probes

18. Light Probes

19. Light Probes

20. Light Probes
●
No dynamic lights
●
No self-illumination of dynamic objects

21. Light Propagation Volumes

22. Light Propagation Volumes

23. Light Propagation Volumes

24. Light Propagation Volumes

25. Light Propagation Volumes
No propagation

26. Light Propagation Volumes
After 4 iterations

27. Light Propagation Volumes
After 6 iterations

28. Light Propagation Volumes
After 8 iterations

29. Light Propagation Volumes

30. Light Propagation Volumes

31. Light Propagation Volumes
●
Dynamic lights
●
No indirect shadows
Light Propagation Volumes

32. Voxel Cone Tracing
Algorithm
●
Voxelize the geometry
●
Construct sparse voxel octree (SVO)
●
Inject direct lighting into the octree
●
Propagate radiance
●
Gather radiance by cone tracing

33. Voxel Cone Tracing

34. Voxel Cone Tracing
Voxelization

35. Voxel Cone Tracing
Sparse Quad-tree

36. Voxel Cone Tracing
Sparse Voxel Octree

37. Voxel Cone Tracing

38. Voxel Cone Tracing
Light injection

39. Voxel Cone Tracing
Filtering up

40. Voxel Cone Tracing
Voxel Cone Tracing

41. Voxel Cone Tracing

42. Voxel Cone Tracing

43. Voxel Cone Tracing
37 ms
32 ms
14 min

44. Voxel Cone Tracing
●
Dynamic lights & objects
●
Shadow casting
●
Huge amount of memory

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