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Practical Notes & Performance (FOW)

Practical Notes

  • Keep instances few: Merge nearby areas; each Fog Instance has its own RT and full pipeline.
  • Start settings: UpdateRate ≈ 0.2 s, Hierarchical DDA, LOD on 4, mild Blur.
  • Skip occlusion when you can: If blockers aren’t needed or added, system automatically skips raymarches.
  • Captures: If you use it, prefer ShowOnly + bUpdateOnlyIfTransformChanged so you don’t recapture and recalculate the occlusion textures every update.
  • Batch queries: Try to always use the batched GPU readback API, not many single queries.
  • Edge sanity: Keep Actor Visibility Cutoff slightly above ExploredValue.
  • If an actor also blocks: add EyeOffset so it doesn’t self-occlude.
  • Use the right raymarch method for your use case If occlusion is not updated very often, prefer Distance Field, otherwise try using Hierarchical DDA. If there is a lot of height below the vision sources, which does not occlude, try any of the other ones.

Cost Hotspots

GPU

  • Occlusion rebuilds: Coverage/Height write, max-mip pyramid, optionally a Distance Field in multiple passes.
  • Visibility pass: per-pixel loops over vision sources and ray marches if pixel is in its area (reduced by binning them into tiles first), then optional blur.

Important Settings

  • Update cadence: Try to recalcualte the fog value as rarely as possible, smooth masks allow to turn this value up higher without artifacts (High Blur and Falloff).
  • LOD compute: reduces the resolution of the internal textures for the shader. Get later on upscaled to the final resolution. Also works best with smooth masks.
  • Blur: Too high settings can quickly become very costly. However, use it to smooth the mask, primarly on occlusion edges, so that you can use a more coarse LOD level.
  • DFScale (if DF): 2–4 to shrink DF cost without visible artifacts.

Choosing a Ray Method

The plugin comes with 4 raymarching methods. The best one depends on your use case. If occlusion is recomputed rarely, prefer Distance Field. If it is updated frequently, prefer Hierarchical DDA. However, as Hierarchical DDA only does the height test at the finest level, it can quickly become slow if there is a lot of height which does not actually occlude the ray. If this is the case, try using any of the other methods.