In 2018.1 we removed the preview label from the Progressive Lightmapper – we’ve made memory improvements, optimizations, and have had customers battle test it. We are now also working on a GPU accelerated version of the lightmapper. In this session, Tobias and Kuba will provide an intro to the basics of lightmapping and address of the most common issues that users struggle with and how to solve them. They will also provide an update on the future roadmap for lightmapping in Unity. Tobias Alexander Franke & Kuba Cupisz (Unity Technologies)

1. Kuba Cupisz &
Tobias Alexander Franke
Progressive Lightmapper: An introduction to lightmapping
in Unity
Unity Technologies

2. Progressive Lightmapper:
An introduction to
lightmapping in Unity

3. Who are we?
Kuba
Cupisz
Tobias Alexander
Franke

4. The problem with
Lightmapping...
press
wait…

5. Milliseconds

6. Progressive updates View prioritization

7. Today’s menu
• Optimizing content for the Progressive Lightmapper
• i.e. “What can you do to make baking faster”
• A sneak peak into the GPU backend for the Progressive Lightmapper
• i.e. “What we are doing to make baking faster”
• Future developments
• i.e. “What we have in store to make baking more convenient”

8. Part 1: Optimizing
baking in the
Progressive
Lightmapper

9. Global
Illumination:
Gambling with
photons until
you think you
have won

10. Lightmapping at a glance

11. An overview of the parameters
• Direct Samples
• Number of rays shot towards light sources
• Indirect Samples
• Number of paths shot in the upper hemisphere
• Bounces
• Number of times a ray is allowed to bounce of another surface

12. An overview of the parameters

13. An overview of the parameters

14. An overview of the parameters

15. Understanding texels
• Pixels in lightmap
• Mapped to units of space
• Texel count is proportional to resolution^2
• Each texel spawns:
• n direct rays towards k lights
• m indirect rays * j bounces
• one direct ray per bounce towards k lights
• Texels are the amount of work to do
• Texels are the amount of work to

16. 1 Texel per Unit 2 Texels per Unit 5 Texels per Unit

17. You don’t need to bake texels if you
don’t put them into the lightmap!

18. Keep a low texel count
• Do not waste (a lot of) texels on these:
• Surfaces with low variation
• Surfaces which receive indirect bounce light only
• Small objects
• Thin objects
• Surfaces hidden from the player

19. Albedo Baked Lightmap Shaded

20. Scale objects with low variation
• Scale “unimportant” objects to
reduce texel count
• Good targets:
• Small objects
• Objects which receive almost
uniform lighting
• e.g. the wall in the back
Can be represented with few texels
Needs many texels,
otherwise shadow will be blurry

21. Light Modes
• Subtractive
• Baked direct and indirect
• Shadowmask
• Save additional lightmap information to composite realtime and baked
shadows correctly
• Indirect only
• Baked indirect only
• Realtime direct light and shadows

22. Shadowmask/Subtractive Baked Indirect

23. Remove small/low-influence
objects entirely

24. Remove small/low-influence
objects entirely

25. Probe lighting
• Use probes for small or thin objects, and for
small-ish objects that would use too many texels
• Fences
• Wires
• Tubes
• Trees
• “Decoration”
• …
• Quick to compute, fairly low lookup cost

26. (not)Lightmapping LODs
• Marking all LODs in an LOD Group as lightmap static
• Each renderer gets lightmap texels
• Slow bakes
• Lower LODs need to be processed one by one
• Not enough work to saturate the hardware
• Raytracer’s acceleration structure needs to be changed
• Can be slow

27. (not)Lightmapping LODs - projection
• Marking only LOD0 in an LOD Group as lightmap static
• Only renderers in LOD0 get lightmap texels
• Lower LODs reuse those texels
• UVs need to match between LOD levels
• Same UV island outline, simpler topology inside
• Bakes are fast again
• All renderers processed in one go
• Raytracer’s acceleration structure is static

28. (not)Lightmapping LODs - projection
Matching UVs

29. (not)Lightmapping LODs - projection
27.5k/13.7k/6.9k triangles

30. (not)Lightmapping LODs - projection
Same distance

31. (not)Lightmapping LODs - projection
Actual usage in game

32. (not)Lightmapping LODs - projection
• Will be released as scripts soon
• Copy lightmap scale/offset and lightmap index
• From LOD0 to lower LODs
• Fully built-in in one of the coming releases

33. Filtering
• Post process to filter out noise by applying a “blur”
• Two variants
• Gaussian
• Edge-Aware A-Trous
• Used to fix small amounts of noise
• How NOT to optimize
• Lower sample count to bake fast
• Counter noise with more filtering

34. 400 Samples Gauss Filter A-Trous Filter 400K Samples

35. 400 Samples Gauss Filter A-Trous Filter 400K Samples

36. An overview of the parameters
• Lightmap Padding
• Space between UV islands
• Lightmap Size
• Max atlas width/height

37. Part 2: The GPU baking
backend

39. Speedup

40. AMD RadeonRays
• OpenCL based
• Cross platform
• Vendor agnostic
• Wavefront compute based
• Small simple kernels
• Quite a lot of them
• Can fall back to CPU

41. Part 3: The Future

42. The Future
• C# Raytracing API
• Support for multiple GPUs
• in one desktop
• laptop (with internal GPU + eGPUs)
• Features
• MIS
• Better probe handling

43. Take-away
• Minimize texel count for faster baking
• Use probes wherever possible, but most importantly for small objects
• Scale objects in lightmaps if they have low lighting variation
• Use appropriate light modes
• Try to avoid baking high-frequency details
• Indirect light is usually very blurry/low-frequency, no need for many texels
• GPU Lightmapper
• Future development

44. Thank you!

45. Q&A