LOD and Culling Systems That Scale - Unite LA
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How we used ECS to display a large environment in the Unite LA streaming demo. Speaker: Mike Acton (Unity Technologies)
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LOD and Culling Systems That Scale - Unite LA
- 1. LOD and Culling Systems That Scale Mike Acton
- 6. Culling • Per view frustum (6-18 culling planes) • 5 views in this sample (main camera + shadow cascades) • Deep hierarchy (nested prefabs) • ~30-200K instances per section (e.g. single building) • ~5M instances in scene (whole scene in editor)
- 7. Culling • What’s not surprising? • World is static. • Flatten hierarchy.
- 10. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds
- 11. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds • Flat list of 5M instances • Next step? • Hierarchical spatial tree? • What’s our data look like?
- 12. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds • 16K Chunks of component data • Subscenes roughly spatial
- 13. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds ChunkWorldRenderBounds • ~60K Chunks • (For each view)
- 14. Culling • Another level of hierarchy? • Take a look at the data we have again…
- 19. LocalToWorld LocalToWorld LocalToWorld LocalToWorld LocalToWorld LocalToWorld MeshRenderer MeshRenderer 0 1 2 3 4 5 1 4 5 - - - • Render Batch Index List • Same Mesh Renderer • Max 1023 instances
- 20. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds • Chunks • SharedComponent MeshRenderer
- 21. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds • Chunks • SharedComponent MeshRenderer LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds MeshRenderer
- 23. LocalToWorld LocalToWorld LocalToWorld LocalToWorld LocalToWorld LocalToWorld MeshRenderer MeshRenderer • Looks a like like what we need for render batch
- 24. Chunk A Chunk B Chunk C Chunk D Chunk E Chunk F • Render Batch = NativeArray of Chunks • …Gives us second-level hierarchy
- 25. Chunk A Chunk B Chunk C Chunk D Chunk E Chunk F • Different streaming subcenes? Chunk A Chunk B Chunk C Chunk D Subscene A Subscene B
- 26. Chunk A Chunk B Chunk C Chunk D Chunk E Chunk F [Aside] Let’s go back to… Render Batch = NativeArray of Chunks Is this safe?
- 27. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C
- 28. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C Check OrderVersion of Required Components (ABC)
- 29. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C Order Outside Set has changed.
- 30. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C
- 31. EntityManager.GetComponentOrderVersion A A A A A A A A A B B B B B B C C C
- 32. EntityManager.GetComponentOrderVersion A A A A A A A A B B B B B B C C C A
- 33. EntityManager.GetComponentOrderVersion A A A A A A A A B B B B B B C C C A 1 0 0
- 34. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C Order Inside Set has changed.
- 35. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C
- 36. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C Cause B,C to change archetype
- 37. EntityManager.GetComponentOrderVersion A A A A A A A A A A B B B B B B C C C Cause B,C to change archetype
- 38. EntityManager.GetComponentOrderVersion A A A A A A A A A B B B B B B C C C
- 39. EntityManager.GetComponentOrderVersion A A A A A A A A A B B B B B B C C C
- 40. EntityManager.GetComponentOrderVersion A A A A A A A A A B B B B B B C C C
- 41. EntityManager.GetComponentOrderVersion A A A A A A A A A B B B B B B C C C 1 1 1 All Required Component Order Versions changed = Chunks invalid
- 42. Chunk A Chunk B Chunk C Chunk D Chunk E Chunk F [Aside] Let’s go back to… Render Batch = NativeArray of Chunks Is this safe? Yes.
- 43. Culling loop is Simple. Render Batch Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index
- 44. Culling loop is Simple. (Batches in parallel) Render Batch Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Render Batch Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Chunk ChunkRenderBounds WorldRender Bounds WorldRe Boun Batch Index Batch Index
- 45. LOD • What about LOD? • Flatten similar to transform hierarchy • But still LOD groupings…
- 46. LocalToWorld LocalToWorld LocalToWorld LOD 0 LocalToWorld LocalToWorld LocalToWorld LOD 0 LOD 1 LOD 1 HLOD 0 HLOD 1
- 47. LOD • What about LOD? • Most instance LODs are unique (not mesh combinations)
- 48. LocalToWorld LocalToWorld LocalToWorld LOD 0 LocalToWorld LocalToWorld LocalToWorld LOD 0 LOD 1 LOD 1
- 49. LocalToWorld LocalToWorld LocalToWorld LOD 0 LocalToWorld LocalToWorld LocalToWorld LOD 0 LOD 1 LOD 1 LOD 0 LOD 0
- 50. LOD • What about LOD? • Most instance LODs are unique (not mesh combinations) • What about HLOD?
- 51. LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds Chunks by • Same Renderer • Same Subscene MeshRenderer LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds LocalToWorld WorldRenderBounds ChunkWorldRenderBounds MeshRenderer Subscene A Subscene B 99+% of chunks have only one HLOD root
- 52. LocalToWorld LocalToWorld LocalToWorld LOD 0 LocalToWorld LocalToWorld LocalToWorld LOD 0 LOD 1 LOD 1 LOD 0 LOD 0 HLOD 0 5 HLOD 1 1
- 53. LOD loop is Simple. Chunk HLOD LOD LOD LOD LOD HLOD LOD LOD LOD LOD Packed Potentially Visible Bitset
- 54. LOD loop is Simple. (Chunks in parallel.) Chunk HLOD LOD LOD LOD LOD HLOD LOD LOD LOD LOD Chunk HLOD LOD LOD LOD LOD LOD LOD
- 55. Putting them together LOD (All Chunks) Cull (View 0) Cull (View 1) Cull (View 2) Cull (View 3) Cull (View 4)
- 56. Look at culling loop again… Render Batch Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index
- 57. Early out based on LOD visibility Render Batch Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Chunk ChunkRenderBounds WorldRender Bounds WorldRender Bounds Batch Index Batch Index Any LOD Visible? Any LOD Visible?
- 58. Recap • Simple culling loop • Simple LOD loop • Because we could reason about how data was stored… • …and some basic statistics about that data.
- 59. Key to Data-Oriented Practice = Data Transparency