Fog of war: underground is black until the bot has seen it (t8)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-24 01:37:34 -04:00
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+# Fog of war
+
+Unexplored ground is black with a soft edge. The sky and the first few grains of the
+surface start seen. Exploration never changes the simulation.
+
+## Data and revealing
+
+`src/sim/fog.js` keeps a `Uint8Array` at half the grain resolution (`FOG = 2`).
+Values run from 0 (unseen) to 255 (seen) and only increase. `alloc` allocates it with
+the other world arrays. `fogInit` reveals above `surfY` and fades eight grains below it.
+
+Every four ticks, 256 rays from the bot's centre reveal up to 48 grains. The last eight
+grains fade out. Solid and powder stop sight after a four-grain fade into their face;
+air, gas and liquid pass sight. Bars and machine voids do not block it.
+
+## Saving
+
+The fog buffer is saved and exported with the other typed arrays, without a save version
+change. Older saves rebuild the surface, reveal a radius of 12 grains around built blocks,
+machine footprints and molds, then look from the bot. Loading and generating also look
+immediately from the bot.
+
+## Drawing and setting
+
+Both looks and the thermal lens sample fog bilinearly. Seen grains use the usual drawing;
+unseen grains use the out-of-world colour and smooth-look buffers, hiding their shapes.
+Partial values dim foreground, background and trees. Bloom sources need at least 128;
+bars, flyers, rain and particles need at least 64. Hover info and the cursor label say
+only “Unexplored” below 64.
+
+Game settings → Fog of war is on by default. Turning it off shows the whole world while
+exploration continues to be recorded and saved. Browser scenes and performance tools turn
+it off in their shared setup; dedicated fog checks enable it explicitly.