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Progressive Lightmapper: An Introduction to Lightmapping in Unity
The document serves as an introduction to the Progressive Lightmapper in Unity, detailing optimization techniques for faster light mapping and the overall mechanics involved in the baking process. It includes practical tips for managing texel counts, understanding light modes, and utilizing GPU capabilities for improved performance. Future developments mentioned include support for multiple GPUs and enhanced probe handling.
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Progressive Lightmapper: An Introduction to Lightmapping in Unity
- 1. Kuba Cupisz & TobiasAlexander Franke Progressive Lightmapper: An introduction to lightmapping in Unity Unity Technologies
- 2. Progressive Lightmapper: An introductionto lightmapping in Unity
- 3. Who are we? Kuba Cupisz TobiasAlexander Franke
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- 6. Progressive updates Viewprioritization
- 7. Today’s menu • Optimizingcontent 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 bakingin the Progressive Lightmapper
- 9. Global Illumination: Gambling with photons until youthink you have won
- 10. Lightmapping at aglance
- 11. An overview ofthe 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 ofthe parameters
- 13. An overview ofthe parameters
- 14. An overview ofthe parameters
- 15. Understanding texels • Pixelsin 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 perUnit 2 Texels per Unit 5 Texels per Unit
- 17. You don’t needto bake texels if you don’t put them into the lightmap!
- 18. Keep a lowtexel 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 LightmapShaded
- 20. Scale objects withlow 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
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- 25. Probe lighting • Useprobes 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 • Markingall 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 processto 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 GaussFilter A-Trous Filter 400K Samples
- 35. 400 Samples GaussFilter A-Trous Filter 400K Samples
- 36. An overview ofthe parameters • Lightmap Padding • Space between UV islands • Lightmap Size • Max atlas width/height
- 37. Part 2: TheGPU baking backend
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- 40. AMD RadeonRays • OpenCLbased • Cross platform • Vendor agnostic • Wavefront compute based • Small simple kernels • Quite a lot of them • Can fall back to CPU
- 41. Part 3: TheFuture
- 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 texelcount 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
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