Spawning Overhaul

A Minecraft mod that creates a more immersive mob spawning system based on environmental factors like caves, forests, and structures.

Features

Environment-Based Spawning

Instead of mobs spawning uniformly everywhere, this mod makes spawning rates dependent on the spawn location's environment:

• Base Multiplier: Configure a global spawn rate that applies everywhere (default: 0.2x)
• Cave Spawning: Progressive scaling based on depth
  • Shallow caves (Y=60): Minimum multiplier (default: 1.0x = 20% acceptance)
  • Deep caves (Y=-64): Maximum multiplier (default: 5.0x = 100% acceptance)
  • The deeper you go, the more dangerous it gets!
• Forest Spawning: Progressive scaling based on tree density
  • Sparse areas: Minimum multiplier (default: 1.0x)
  • Dense forests/jungles: Maximum multiplier (default: 3.0x)
  • More trees = more danger
• Structure Spawning: Dangerous structures have increased spawn rates (default: 3.0x)
  • Strongholds, Nether Fortresses, Ocean Monuments, Woodland Mansions, Mineshafts, Dungeons

Note: Spawn multipliers use normalized probability acceptance based on the highest configured multiplier. With default settings (maxCaveMultiplier = 5.0), the reference is 5.0x:

• 0.2x base = 4% acceptance (0.2/5.0)
• 1.0x shallow caves = 20% acceptance (1.0/5.0)
• 5.0x deep caves = 100% acceptance (5.0/5.0)

This creates dramatic contrast: deep caves have 25x more spawns than the surface!

Mob-Specific Rules

Configure special spawn restrictions for specific mobs:

• Spider Only In Cave (Enabled by default)

  • When enabled: Spiders and cave spiders only spawn in caves
  • When disabled: Spiders spawn normally everywhere

• Disable Creeper Near Structure (Disabled by default)

  • When enabled: Prevents creepers from spawning in dangerous structures (protects against griefing)
  • When disabled: Creepers spawn normally in structures

In-Game Debug Command

Use /spawndebug to see what spawn rates would apply at your current position:

• Environment detection at your position (cave, forest density, structure)
• Active spawn multipliers and their ranges
• Which multiplier would be used (base, cave, or forest)
• Final calculated spawn rate if a mob were to spawn here

This shows you what the spawn system "sees" at your position.

Requires operator level 2 (use /op <username>)

Configuration

The mod creates a config file at config/spawningoverhaul.json5

Accessing the Config GUI

Fabric:

• Install Mod Menu
• Click "Mods" in the main menu
• Find "Spawning Overhaul" and click the config button

NeoForge:

• Click "Mods" in the main menu
• Find "Spawning Overhaul" and click "Config"

Configuration Options

Environmental Multipliers

Mob-Specific Rules

Detection Settings

Mod Compatibility

How It Works

Spawn Calculation

For each mob spawn attempt, the mod:

1. Detects the environment at the spawn location (not the player's location):

   • Is the spawn position in a cave? What's the depth?
   • How dense is the forest at that position? (counts nearby log blocks)
   • Is the spawn position in a dangerous structure?

2. Calculates multipliers:

   • Starts with the base multiplier
   • Calculates cave multiplier (if in cave)
   • Calculates forest multiplier (if logs detected)
   • Selects the highest of: base, cave, or forest

3. Applies additional modifiers:

   • Multiplies by structure multiplier (if in dangerous structure)
   • Applies mob-specific rules (spiders, creepers)

4. Makes the spawn decision:

   • All multipliers use probabilistic acceptance normalized to the highest configured multiplier
   • The reference maximum is dynamically calculated from config (max of cave/forest/structure multipliers)
   • Higher multipliers = higher acceptance probability = more spawns
   • Examples (with default 5.0x reference from maxCaveMultiplier):
     • 0.2x → 4% acceptance (very few spawns)
     • 1.0x → 20% acceptance (reduced spawns)
     • 3.0x → 60% acceptance (structures, many spawns)
     • 5.0x → 100% acceptance (deep caves, maximum spawns)
   • Multiplier = 0.0: Always denies spawn

Performance

The mod is designed to be lightweight:

• Cave detection: Simple Y-coordinate check + sky visibility
• Forest detection: Cylindrical scan limited to ±3 blocks vertically
• Structure detection: Cached with 10-second TTL
• Target impact: <2ms per spawn check on average

Compatibility

✅ Compatible With

• Modded mobs: Automatically works with any mob from any mod
• Modded structures: Use config lists to mark modded structures as dangerous/safe
• Modded biomes: Works in all biomes (vanilla and modded)
• Other spawn mods: Applies after vanilla spawn checks, stacks with other mods

⚠️ Known Limitations

• Does not affect mob spawners (only natural spawns)
• Does not affect event spawns (raids, boss fights, etc.)
• Does not affect command summons (/summon)
• First spawn in each chunk may be slightly slower due to cache misses