Performance Roadmap

[kring]

This issue is an inventory of issues and ideas for improving Cesium for Unreal's performance. While we think the performance is pretty good, improved performance has a major impact on the user experience, so it's worth investing in.

This is a work in progress, please add to it!

Potentially High Impact

After a lot of profiling, here are the most impactful ideas for performance we currently have:

Frame Rate Improvements

• Add resource creation throttling + mip map generation cesium-native#565
• Various performance improvements #975 ( Async texture creation / better threading / better destruction)
• Investigate and reduce garbage collector pressure (UObject pooling?) #980
• Create RHI vertex and index buffers asynchronously #982

Latency Reduction

• Cache render content _after_ loading cesium-native#566 (WIP: Implement derived content caching #990)
• Add ability to cancel / reprioritize tile loads after the network request cesium-native#564

Other Ideas

A longer, more complete list of performance-related tasks and ideas - feel free to bump any of these ideas up to the above list if investigation shows it would yield significant improvements:

Tile Selection Improvements

Improvements to the algorithm that decides which tiles to render and which tiles to load and unload, and in what order.

• Leverage Hardware Occlusion Queries in Tileset Traversal #818
• Allow non-linear screen space error cesium-native#342
• Use child tile bounding volumes to cull parent tiles cesium-native#506
• Implicit tileset refinement fails to skip LODs cesium-native#483
• Implement predictive 3D Tiles loading from CesiumJS cesium-native#85
• Implement dynamic 3D Tiles SSE adjustment from CesiumJS cesium-native#86
• Add option to preload a tileset or section of a tileset cesium-native#266
• Avoid holes in terrain while loading cesium-native#269
• Add global cache to unload any tilesets that are not in view cesium-native#246

Load Pipeline Improvements

Improvements to the process that loads tiles from the network and prepares them for rendering.

• CesiumGltf objects stored in a vector get copied rather than moved on resize cesium-native#375
• Reduce texture copies, perhaps by uploading directly from ImageCesium to GPU? #865
• Investigate faster collision mesh generation/loading options #512
• In the load pipeline, separate the network request from the post-download CPU work, and throttle them differently cesium-native#473
• Large tilesets produce performance warning when building map #826
• Cesium sets global material parameters unnecessarily #814
• Remove glTF compressed buffers after decompressing cesium-native#107
• Cache and reuse render resources for external images cesium-native#497
• Schedule the "main thread" part of tile loading more intentionally cesium-native#507

Rendering Improvements

Improvements to the actual rendering of tiles.

• Improve transitions between tile LODs #508
• Merge raster tiles from different sources for better performance and to save texture units cesium-native#88
• Investigate generating materials at editor time, rather than using an uber-shader #866
• Consider setting texture sampler sources to Shared:Wrap #490
• Add "mip bias" as a tileset option cesium-native#518
• Use async texture creation for encoded metadata tables #979