Source Engine BSP Compiler Incremental Rebuild Limitation After Texture Changes

Texture Scale Modifications Require Full BSP Recompile

The Source engine's standard compile pipeline (VBSP, VVIS, VV) processes entire map geometry and lighting models during each build. When a single texture's scale or material parameter is modified, the compiler does not recognize this as an isolated change and instead rebuilds all lighting data from scratch.

This behavior prevents repeatable development iterations, as level designers cannot rely on incremental updates to reflect minor texture adjustments. The compile cache generated during prior builds does not track source texture metadata, meaning stale lightmap resolutions persist across rebuilds unless intermediate files are manually cleared.

The issue affects all Source engine variants including GoldSrc and Source 2013, creating a consistent bottleneck in modding workflows where rapid iteration on materials is required.

Which specific texture or material metadata changes trigger a full rebuild versus being handled incrementally, and how can developers identify when a clean rebuild is actually necessary versus when intermediate file management is sufficient?