[MC-303542] Structure jigsaw generation sometimes fails when a structure changes elevation

I have created a road template pool called street with projection “terrain_matching”:

{
  "elements": [
    {
      "element": {
        "element_type": "minecraft:legacy_single_pool_element",
        "location": "hollowvoid:void_village/street",
        "processors": {
          "processors": []
        },
        "projection": "terrain_matching"
      },
      "weight": 1
    }
  ],
  "fallback": "minecraft:empty"
}

and it contains jigsaws of lamp pointing upwards (image attached).
the template pool of the lamp (rigid):

{
  "elements": [
    {
      "element": {
        "element_type": "minecraft:legacy_single_pool_element",
        "location": "hollowvoid:void_village/lamp",
        "processors": {
          "processors": []
        },
        "projection": "rigid"
      },
      "weight": 1
    }
  ],
  "fallback": "minecraft:empty"
}

street’s nbt is height of 2, when the street is generated on flat surface the lamps placed properly.
but when the terrain exceed initial y for more than 2 blocks the lamps are not being generated anymore.
this can be easily fixed upwards by making the street box height of 10, then then lamp will generate as long as the terrain exceeds up to 10 blocks upwards.
but I couldnt find a solution what if the terrain generates downwards.

Environment

minecraft 1.21.10

Attachments

pack.zip

Comments 5

zahar 2025-10-24T10:05:14Z

As a workaround (im working with fabric) i created mixin that simply expands the structure box in Y direction, so that the jigsaw block will be included inside the structure allowing the lamp to generate:

@Mixin(targets = "net.minecraft.structure.pool.StructurePoolBasedGenerator$StructurePoolGenerator")
public class StructurePoolGeneratorMixin {
    @ModifyVariable(method = "generatePiece", at = @At("STORE"), ordinal = 0)
    private BlockBox onGeneratePiece(BlockBox box) {
        return box.expand(0,10,0);
    }
}

[Mod] ManosSef 2025-10-24T15:05:49Z

We do not have enough resources to reproduce this issue.

Please attach a minimal setup data pack that can be used to reproduce this issue.

_{This issue is being temporarily resolved as}_{Awaiting Response}_{. Once the requested information has been delivered, the report will be reopened automatically.}

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zahar 2025-10-24T15:27:05Z

I don't see any attach button. Moreover the screenshots attachments disappeared as well.
I can send via email if its an option.

[Mod] ManosSef 2025-10-24T15:38:56Z

You can attach files to comments.

zahar 2025-10-24T17:00:54Z

Here, try to `/place structure my_namespace:test_street` on flat surface vs sloped.
you can even see mid way when it stops working, both upwards and downwards (no workaround for downwards except code change)

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