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Structure processors modify blocks during structure generation. Lithostitched adds several powerful processor types beyond vanilla’s capabilities.

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Processor Types

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ReferenceStructureProcessor

References and applies multiple processor lists in sequence.
​
processor_type
string
required
Must be "lithostitched:reference"
​
processor_lists
HolderSet<StructureProcessorList>
required
Tag or list of processor lists to apply. Processors are applied in order.

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Example

Apply multiple processor lists from a tag: 
{
  "processors": [
    {
      "processor_type": "lithostitched:reference",
      "processor_lists": "#mymod:dungeon_processors"
    }
  ]
}
Tag definition (data/mymod/tags/worldgen/processor_list/dungeon_processors.json): 
{
  "values": [
    "mymod:weathering",
    "mymod:mob_spawners",
    "mymod:loot_chests"
  ]
}

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Java Implementation

public class ReferenceStructureProcessor extends StructureProcessor {
    private final HolderSet<StructureProcessorList> processorLists;
    
    @Override
    public StructureBlockInfo processBlock(...) {
        StructureBlockInfo processedBlock = absolute;
        
        for (Holder<StructureProcessorList> processorList : this.processorLists) {
            for (StructureProcessor processor : processorList.value().list()) {
                processedBlock = processor.processBlock(...);
                if (processedBlock == null) return null;
            }
        }
        
        return processedBlock;
    }
}
Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/ReferenceStructureProcessor.java:31

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ConditionProcessor

Applies different processors based on a condition evaluation.
​
processor_type
string
required
Must be "lithostitched:condition"
​
if_true
ProcessorCondition
required
Condition to test. See Processor Conditions for available types.
​
then
StructureProcessor[]
required
Processors to apply if condition is true.
​
else
StructureProcessor[]
default:"[]"
Processors to apply if condition is false.
​
random_mode
RandomSettings
default:"{\"mode\": \"per_block\"}"
Controls random source creation. See Random Settings.

​
Example: Replace Degraded Blocks

Replace blocks with weathered variants based on random chance: 
{
  "processor_type": "lithostitched:condition",
  "if_true": {
    "type": "lithostitched:random_chance",
    "chance": 0.3
  },
  "then": [
    {
      "processor_type": "minecraft:rule",
      "rules": [
        {
          "input_predicate": {
            "block": "minecraft:stone_bricks"
          },
          "location_predicate": {
            "predicate_type": "minecraft:always_true"
          },
          "output_state": {
            "Name": "minecraft:cracked_stone_bricks"
          }
        }
      ]
    }
  ],
  "else": []
}

​
Example: Position-Based Processing

Apply different blocks based on position: 
{
  "processor_type": "lithostitched:condition",
  "if_true": {
    "type": "lithostitched:position",
    "min_y": 0,
    "max_y": 10
  },
  "then": [
    {
      "processor_type": "lithostitched:set_block",
      "state_provider": {
        "type": "minecraft:simple_state_provider",
        "state": {
          "Name": "minecraft:deepslate_bricks"
        }
      }
    }
  ],
  "else": [
    {
      "processor_type": "lithostitched:set_block",
      "state_provider": {
        "type": "minecraft:simple_state_provider",
        "state": {
          "Name": "minecraft:stone_bricks"
        }
      }
    }
  ]
}
Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/ConditionProcessor.java:60

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BlockSwapStructureProcessor

Swaps specific blocks with replacements using a map.
​
processor_type
string
required
Must be "lithostitched:block_swap"
​
blocks
Map<ResourceKey<Block>, ResourceKey<Block>>
required
Map of source block keys to replacement block keys. Properties are preserved when possible.

​
Example: Wood Type Swap

Change oak structures to birch: 
{
  "processor_type": "lithostitched:block_swap",
  "blocks": {
    "minecraft:oak_log": "minecraft:birch_log",
    "minecraft:oak_planks": "minecraft:birch_planks",
    "minecraft:oak_stairs": "minecraft:birch_stairs",
    "minecraft:oak_slab": "minecraft:birch_slab",
    "minecraft:oak_fence": "minecraft:birch_fence",
    "minecraft:oak_door": "minecraft:birch_door",
    "minecraft:oak_trapdoor": "minecraft:birch_trapdoor"
  }
}
Source: /home/daytona/workspace/source/src/common/main/resources/data/lithostitched/worldgen/processor_list/shipwreck_palette/oak_and_birch.json:4

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Example: Stone Variants

Create ruined structures with different stone types: 
{
  "processor_type": "lithostitched:block_swap",
  "blocks": {
    "minecraft:stone_bricks": "minecraft:mossy_stone_bricks",
    "minecraft:stone_brick_stairs": "minecraft:mossy_stone_brick_stairs",
    "minecraft:stone_brick_slab": "minecraft:mossy_stone_brick_slab"
  }
}

​
Block State Preservation

The processor preserves block properties when possible: 
if (newBlock.isPresent()) {
    return new StructureBlockInfo(
        currentBlockInfo.pos(), 
        newBlock.get().value().withPropertiesOf(currentBlockInfo.state()), 
        currentBlockInfo.nbt()
    );
}
This means stairs keep their facing, slabs keep their type, etc. Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/BlockSwapStructureProcessor.java:46

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ApplyRandomStructureProcessor

Randomly selects and applies one processor list from a set.
​
processor_type
string
required
Must be "lithostitched:apply_random"
​
processor_lists
HolderSet<StructureProcessorList>
required
Tag or list of processor lists. One is randomly selected per block/piece (based on mode).
​
mode
RandomSettings
required
Controls randomization scope. See Random Settings.

​
Example: Per-Piece Palette Selection

Randomly select a shipwreck wood palette per structure: 
{
  "processor_type": "lithostitched:apply_random",
  "mode": "per_piece",
  "processor_lists": "#lithostitched:shipwreck_palettes"
}
Source: /home/daytona/workspace/source/src/common/main/resources/data/lithostitched/worldgen/processor_list/shipwreck.json:4 Tag definition (data/lithostitched/tags/worldgen/processor_list/shipwreck_palettes.json): 
{
  "values": [
    "lithostitched:shipwreck_palette/oak_and_birch",
    "lithostitched:shipwreck_palette/oak_and_spruce",
    "lithostitched:shipwreck_palette/spruce_and_dark_oak",
    "lithostitched:shipwreck_palette/dark_oak_and_jungle",
    "lithostitched:shipwreck_palette/jungle_and_spruce",
    "lithostitched:shipwreck_palette/dark_oak_and_spruce"
  ]
}

​
Weighted Selection

Use weighted lists for uneven probability: 
{
  "processor_type": "lithostitched:apply_random",
  "mode": "per_block",
  "processor_lists": [
    {
      "weight": 10,
      "data": "mymod:common_variant"
    },
    {
      "weight": 3,
      "data": "mymod:uncommon_variant"
    },
    {
      "weight": 1,
      "data": "mymod:rare_variant"
    }
  ]
}
Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/ApplyRandomStructureProcessor.java:31

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SetBlockProcessor

Sets blocks to a specific state using a state provider.
​
processor_type
string
required
Must be "lithostitched:set_block"
​
state_provider
BlockStateProvider
required
Provider for the block state to place. Can use any vanilla state provider.
​
preserve_state
boolean
default:"true"
If true, copies block properties from the original block to the new block where possible.
​
random_mode
RandomMode
default:"per_block"
How to seed the random source: "per_block" or "per_piece".
​
block_entity_modifier
RuleBlockEntityModifier
default:"passthrough"
Modifies or clears block entity data. Default preserves existing NBT.

​
Example: Random Stone Variants

Place random stone types: 
{
  "processor_type": "lithostitched:set_block",
  "state_provider": {
    "type": "minecraft:weighted_state_provider",
    "entries": [
      {
        "weight": 3,
        "data": { "Name": "minecraft:stone" }
      },
      {
        "weight": 2,
        "data": { "Name": "minecraft:andesite" }
      },
      {
        "weight": 1,
        "data": { "Name": "minecraft:diorite" }
      }
    ]
  },
  "preserve_state": false,
  "random_mode": "per_block"
}

​
Example: Preserve Properties

Replace block type while keeping orientation: 
{
  "processor_type": "lithostitched:set_block",
  "state_provider": {
    "type": "minecraft:simple_state_provider",
    "state": { "Name": "minecraft:quartz_stairs" }
  },
  "preserve_state": true
}
If the original block is oak_stairs[facing=north,half=top], the result is quartz_stairs[facing=north,half=top]. Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/SetBlockProcessor.java:58

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DiscardInputProcessor

Removes blocks (replaces with air).
​
processor_type
string
required
Must be "lithostitched:discard_input"

​
Example

Clear all blocks (useful in condition processors): 
{
  "processor_type": "lithostitched:discard_input"
}
This processor returns null, which tells the structure system to skip placing this block. Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/DiscardInputProcessor.java:17

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ScheduleTickProcessor

Schedules block and fluid ticks immediately after placement.
​
processor_type
string
required
Must be "lithostitched:schedule_tick"

​
Example

Update water and lava flows: 
{
  "processors": [
    {
      "processor_type": "lithostitched:schedule_tick"
    }
  ]
}
Useful for:
  • Triggering water/lava flow
  • Activating redstone
  • Starting falling block physics
  • Triggering growth for saplings/crops
Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/ScheduleTickProcessor.java:22

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Random Settings

Controls how random sources are created for processors.
​
mode
RandomMode
required
​
name
identifier
default:"lithostitched:default"
Optional identifier for the random source. Different names produce different random sequences.

​
Example Configurations

Simple mode: 
"random_mode": "per_piece"
Full configuration: 
"random_mode": {
  "mode": "per_block",
  "name": "mymod:custom_randomization"
}

​
Random Source Creation

public RandomSource create(WorldGenLevel level, BlockPos piecePos, 
    StructureBlockInfo blockPos) {
    return RandomSource.create(level.getSeed() + this.name.hashCode())
        .forkPositional()
        .at(this.mode.select(piecePos, blockPos));
}
Source: /home/daytona/workspace/source/src/common/main/java/dev/worldgen/lithostitched/worldgen/processor/RandomSettings.java:29

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Processor Lists

Processors are organized into lists for reuse: File: data/mymod/worldgen/processor_list/dungeon_weathering.json 
{
  "processors": [
    {
      "processor_type": "lithostitched:condition",
      "if_true": {
        "type": "lithostitched:random_chance",
        "chance": 0.2
      },
      "then": [
        {
          "processor_type": "minecraft:rule",
          "rules": [
            {
              "input_predicate": { "block": "minecraft:stone_bricks" },
              "location_predicate": { "predicate_type": "minecraft:always_true" },
              "output_state": { "Name": "minecraft:cracked_stone_bricks" }
            }
          ]
        }
      ]
    },
    {
      "processor_type": "lithostitched:condition",
      "if_true": {
        "type": "lithostitched:random_chance",
        "chance": 0.1
      },
      "then": [
        {
          "processor_type": "minecraft:rule",
          "rules": [
            {
              "input_predicate": { "block": "minecraft:stone_bricks" },
              "location_predicate": { "predicate_type": "minecraft:always_true" },
              "output_state": { "Name": "minecraft:mossy_stone_bricks" }
            }
          ]
        }
      ]
    }
  ]
}

​
Common Patterns

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Multi-Stage Processing

Chain processors for complex transformations: 
{
  "processors": [
    // Stage 1: Swap wood types
    {
      "processor_type": "lithostitched:block_swap",
      "blocks": {
        "minecraft:oak_planks": "minecraft:spruce_planks"
      }
    },
    // Stage 2: Add weathering
    {
      "processor_type": "lithostitched:condition",
      "if_true": { "type": "lithostitched:random_chance", "chance": 0.3 },
      "then": [
        { "processor_type": "lithostitched:set_block", "state_provider": { /*...*/ } }
      ]
    },
    // Stage 3: Schedule updates
    {
      "processor_type": "lithostitched:schedule_tick"
    }
  ]
}

​
Biome-Specific Palettes

Combine with conditions for biome-aware processing: 
{
  "processor_type": "lithostitched:condition",
  "if_true": {
    "type": "lithostitched:matching_blocks",
    "block_type": "relative",
    "blocks": "#minecraft:planks"
  },
  "then": [
    {
      "processor_type": "lithostitched:apply_random",
      "mode": "per_piece",
      "processor_lists": "#mymod:biome_palettes"
    }
  ]
}

​
Conditional Block Removal

Remove blocks based on conditions: 
{
  "processor_type": "lithostitched:condition",
  "if_true": {
    "type": "lithostitched:position",
    "min_y": -64,
    "max_y": 0
  },
  "then": [
    { "processor_type": "lithostitched:discard_input" }
  ]
}

​
Best Practices

Define processor lists once and reference them across multiple structures:
// Define once
"data/mymod/worldgen/processor_list/weathering.json"

// Reference many times
"processors": "mymod:weathering"
  • Use per_piece for consistent structure appearance (faster)
  • Use per_block for maximum variation (slower)
// Consistent wood palette across shipwreck
"mode": "per_piece"

// Varied weathering per block
"mode": "per_block"
Use preserve_state: true when block orientation matters:
{
  "processor_type": "lithostitched:set_block",
  "preserve_state": true,
  "state_provider": { /*...*/ }
}
Apply processors in order:
  1. Block swaps (material changes)
  2. Weathering/randomization
  3. Tick scheduling (last)

Processor Conditions

Conditions for conditional processors

Template Pools

Apply processors to pool elements

Block State Providers

Provide block states to processors

Structure Types

Complete structure system

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