Snapshots for GenTerraPostProcess

[tehtelev]

Summary

We've added a thread-safe snapshot system to GenTerraPostProcess, which caches subchunk data in local arrays once before scanning. This dramatically speeds up world generation: millions of slow GetBlockIdUnsafe calls with palette unpacking are replaced with instant index reads. We've also implemented strict array bounds checking and NullReferenceException protection, completely eliminating rare but critical generator crashes caused by non-standard column heights or missing data in chunks.

Type

• Bug fix
• Performance
• New feature
• Refactor or cleanup
• Docs or build

Checklist

• .\scripts\extract-patches.ps1 ran clean.
• dotnet build VintageStory.slnx -c Release is green.
• Every vanilla edit has a // Stratum marker.
• No vanilla source committed.
• Tested on a real server start, not just compilation.

Performance numbers

Tested on the generation of 31417 chunk columns (6 threads) by /stratum pregen start radius 100 16000 16000
Seed - seed 1027995113.
World setting - default.

Three runs were performed before and after the changes using the Jetbrains dotTrace program.

Before

• OnChunkColumnGen method execution time: 5387 ms; 5529 ms; 5561 ms.
• Average: 5492.3 ms
• Standard deviation: 92.6 ms

After

• OnChunkColumnGen method execution time: 3193 ms; 3279 ms; 3236 ms
• Average: 3236.0 ms
• Standard deviation: 43.0 ms

Summary: The snapshot optimization resulted in an average speedup of ~41% (dropping execution time from ~5.5 seconds down to ~3.2 seconds). Additionally, the standard deviation dropped from 92.6 ms to 43.0 ms, indicating significantly more stable and predictable chunk generation performance.