Pollution spread

Owns a pollution value per cell or chunk. Each update, emitters add pollution, a fraction diffuses to neighboring cells, and terrain, vegetation, or water absorb some; other systems read the local value as a penalty to health, land value, crop growth, or happiness. Factorio stores pollution per 32x32-tile chunk, updates every 64 ticks, diffuses 2% to each cardinal neighbor once a chunk holds 15 or more, absorbs it by tile type and trees (trees are damaged above 60), and lets enemy spawners absorb it to fund attack waves. SimCity computes a pollution map from industry and traffic that depresses land value; Cities: Skylines separates ground, noise, and water pollution, and sewage released upstream contaminates water intakes downstream. Inputs are emitter locations and rates; outputs are a spatial field read by other systems.

Growth leaves a visible stain. The player separates factories from homes, plants green buffers, and watches the overlay creep outward; in Factorio a bigger factory directly invites bigger attacks. Cleanup competes with expansion for the same resources.

• emission rate per source and modifiers such as efficiency upgrades or filters
• diffusion fraction, minimum amount before diffusing, and grid resolution
• absorption by terrain, water, and vegetation, and whether absorbers are damaged
• what pollution affects: health, land value, crops, happiness, enemy aggression
• cleanup tools and their cost

• Pollution that only lowers land value is solved once by zoning distance and then ignored.
• Fine-grained diffusion with no threshold or chunking costs compute and produces smeared, unreadable fields.
• Effects carried by hidden channels, such as water contamination far downstream, read as unexplained sickness.

• Zoning separates polluting and sensitive uses, which lengthens commutes and adds traffic.
• In Factorio pollution couples production scale to attack size, so efficiency becomes a defense strategy.
• Absorbers degrade under load, so a polluted region can tip into faster spread as forests die.

• Can learned dispersion surrogates make air and water pollution fields physically plausible while staying cheap and legible?