World Generation

World Generation covers how the terrain, biomes and structures of the Fear Nightfall overworld, Nether and End are chosen and placed. Terrain shape and climate follow vanilla, but the biomes, caves and structures come from dozens of worldgen mods, which the pack balances against each other with a custom biome table. Every biome, structure and cave on the map is therefore the result of a set of pack-wide weights, not of any one mod's defaults.

The pack's theme shows up at the generation level. Horror biomes and horror structures are weighted up, lush caves are weighted down, and the structure sets are thinned or merged so that the map feels sparse and dangerous rather than crowded. A player who wants the detail of any single biome or structure should follow the links below, since each linked page holds its own loot, mobs and placement data.

Biome distribution

The pack replaces the usual competition between mod region weights with one biome source, fnfbiomes:table. The climate noise (temperature, humidity, continentalness, erosion, depth and weirdness) is left alone, so terrain shape and the overall climate layout match vanilla. Inside each climate cell, every biome whose original mod allows it there is eligible, and the biomes share the cell by weight. Same-type biomes are placed next to each other, so forests border forests and deserts border deserts. Oceans, rivers, beaches and caves use the same table.

Before the change, Biomes O' Plenty covered more than half of the land and Terralith about 5%, although both add similar numbers of biomes. The calibrated shares after the change are:

The table covers vanilla, Terralith, Biomes O' Plenty, Regions Unexplored (including its replacement rules), Hexerei, the caves of YUNG's Cave Biomes and Sleepy Hollows (mod). The full list of biomes is on the Biomes page, and the pack's own weighting of horror biomes is described in the World Generation section below.

Terralith and Geophilic both rewrite the vanilla biome files. Whichever loaded last would otherwise win, so the two were merged per biome, with Terralith's features inserted next to their neighbours.

Horror weighting

Horror biomes are given six times the weight of an ordinary biome during selection. The biomes at 6× weight are:

• Ominous Woods and the dark forests of the pack
• Blackwood Taiga and Ashen Woodland
• Sleepy Hollows (mod) and Willow Swamp
• Spider Nest and Ashen Savanna
• Bayou and the dead forests
• Infested Caves and Frostfire Caves
• the Deep Dark

The result is that horror biomes make up 11.9% of the land, up from 4.5%. They concentrate in temperate-to-cool, humid forests, taigas and swamps, where about a quarter of the land is horror. Deserts, jungles and mountain peaks stay mostly ordinary. The mobs and gameplay of these biomes are covered on Horror and Spooky Content.

Sleepy Hollows (mod) and Willow Swamp were especially rare before the change, roughly 2.6 km and 5 km from the nearest instance, so both were made more common.

Caves

Caves use the same biome table as the surface. Two changes make the underground more hostile:

• The horror caves (Infested Caves, Frostfire Caves and Spider Nest) rose from 17–22% of the cave layer to about 30%. Infested Caves, Frostfire Caves and Spider Nest also spread into neighbouring cave areas.
• The lush caves dropped from 12–15% to 4–5%. Fungal Caves and the other cave biomes now share the wide humid range that lush caves used to hold alone.

The caves a player will meet most often are Deep Caves, Mantle Caves, Thermal Caves, Stone Caves, Redstone Caves, Bioshroom Caves, Glowing Grotto, Lost Caves and Frosted Caves. For the ores that sit in these caves and for mining in general, see Ores and Mining.

Structure sets

Structures are not placed by one mod per position. Many mods use shared placement sets, which the pack has merged so that a village, outpost or hut type is chosen from one list. The game picks among the types that are valid for the local biome, so two types never stack on the same spot.

• Villages share a set with vanilla, Luki's Grand Capitals, Overhauled Villages, Towns and Towers Villages, Dungeons and Taverns, Villages&Pillages and the Fortified Villages of Terralith. Each type has equal weight.
• Pillager outposts share a set with vanilla, Luki's Grand Capitals, Towns and Towers and CTOV, with the CTOV outpost weight raised to match the others. See Pillager Outposts.
• Witch huts share a set with vanilla, Luki's Grand Capitals, YUNG's Better Structures, Hexerei Witch Hut, Terralith and the mangrove hut of Dungeons and Taverns. See Witch Huts.

Luki's Grand Capitals replaced the vanilla villages, outposts and witch huts in place when it was first added. Its builds are now separate structures, and the vanilla versions and their loot tables are restored, so both appear. Structures that could only spawn in vanilla biomes (about 15% of land) also spawn in the matching modded biomes, so a modded forest or desert gets its share of structures. Only the mushroom-island structures stay vanilla-only. Every structure set has its own placement seed, so mods that reused a seed no longer land in identical spots.

The broader list of structure families, with their own pages, is on Structures. Some families that matter for the horror theme are The Graveyard (with Graveyards), Born in Chaos, Sleepy Hollows (mod), Covens and the Crypts (Dungeons and Taverns).

Overlap guard

A custom mixin in fnfbiomes stops structures from different sets from colliding. Once a surface structure is assembled, any larger structure from another set that would start nearby is assembled as the game would assemble it, and cached. If their footprints really overlap, the smaller one is skipped. Villages also keep a 6-chunk buffer around other surface structures. The check uses only the world seed, so the result is identical on every machine and does not depend on generation order.

On a 26 km² sample the overlap guard reduced surface overlaps from 238 to 5, and village intrusions from 141 to about 0.

Structure density

Placement spacing is set per structure set with Sparse Structures, which the pack tunes for each set separately (see Structures). The aim is fewer ordinary structures and more horror ones:

• Non-horror structures are about three times rarer than with the mods at default spacing (1,542 down to 492 on the 26 km² sample).
• Horror structures are about twice as common (578 up to 1,071 on the same sample), and they are placed about 30% closer together. Where a horror structure shares a set with other structures, it gets six times the weight.

The horror structures in this group include the Graveyard set, Born in Chaos, Sleepy Hollows (mod), Sons of Sins, the Covens and Witch Huts, the Crypts (Dungeons and Taverns) and the catacombs of Catacombs. Chest contents for these structures are covered on Loot and Chests.

The Nether

The Nether gets its own biome and structure additions from several mods. Regions Unexplored supplies biomes such as Ancient Delta and Blackstone Basin, and Biomes O' Plenty and Terralith supply more. Moog's Nether Structures, Formations, Dungeons and Taverns and Nether Expansion add bridges, ruins, keeps and towers. Examples include Moog's Nether Bridges, Moog's Nether Ruins, the Nether Keep and Port and Jaden's Nether Expansion. The full Nether content is on The Nether.

The Nether and End use hand-picked biome matches for their structures, not the climate-based matching used on the surface.

The End

Biomes O' Plenty adds three highlands biomes to The End: End Wilds, End Reef and End Corruption. The End also has End Mega Ships, End Castle, Lighthouse and Ship and the Moog's End Structures. The dimension is described on The End.

Born in Chaos had added its mobs to the End and Nether in large numbers. Its mobs were 98% of End spawns, so its 41 spawn modifiers now apply only in the overworld, along with Willow Swamp, Sleepy Hollows and two undergrowth biomes that were missed. Overworld spawns are unchanged.

Finding biomes and structures

Nature's Compass is the pack's biome finder. Its recipe was changed to use diamonds in the corners instead of saplings. The compass's search of the climate layout can take a long time for rare biomes. Before a fix, the search exceeded the server's 60 second watchdog and crashed the server, so the pack sets max-tick-time to -1 in server.properties. The same search now takes about 14 seconds. For the in-game tools and commands used to find biomes and structures, see Finding Structures and Biomes.

Fixes to worldgen

Several mod conflicts affected generation and were fixed for the pack:

• Formations and C2ME. Formations' bed-colour processor shared one random generator across chunk threads, which caused exceptions and wrong colours during parallel generation. Each call now uses its own random generator with the same seed, so the colours are unchanged. See Formations.
• Graveyard. Graveyard registered a structure type after the registries had frozen, which crashed generation when another mod touched it. It no longer registers late. See The Graveyard.
• Towns and Towers biome tags. The mod shipped vanilla village, outpost and desert-pyramid tags with replace:true, which removed every Biomes O' Plenty, Regions Unexplored and Terralith addition. The tags were rebuilt as a union. See Towns and Towers.
• YUNG's desert temples and witch huts missed modded deserts and swamps. Their biome tags were extended, and natural generation was confirmed in the Biomes O' Plenty and Regions Unexplored biomes.

Changes apply to new chunks

Generation changes only affect chunks that have not yet been generated. To see the full effect of the pack's worldgen, start a fresh world. Existing worlds keep the terrain and structures that were generated before the changes. For server setup, see Multiplayer and Server Setup. For a first world, see Getting Started.