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Configuring Anti-Xray

Originally written and maintained by PaperMC project

LeviAntiCheat includes an obfuscation-based Anti-Xray with three modes, configurable on a per world basis.

Anti-Xray has three different modes. engine-mode: 1 replaces specified blocks (hidden-blocks) with other "fake" blocks, stone (deepslate at y < 0, specific in config), netherrack, or end_stone based on the dimension. In contrast, engine-mode: 2 will replace both hidden-blocks and replacement-blocks with randomly generated hidden-blocks. engine-mode: 3 works similarly to engine-mode: 2, but instead of randomizing every block, it randomizes the block for each layer of a chunk.

Note: The block will be obfuscated only if it's covered by HiddenBlocks or ReplacementBlocks on all six sides.

The following images1 show how each mode will look for a player using Xray with the recommended configuration in both the overworld and nether.

Overworld Anti-Xray Comparison Nether Anti-Xray Comparison

Especially on the client side, engine-mode: 1 is much less computationally intensive, while engine-mode: 2 may better prevent Xray. With engine-mode: 1, only ores that are entirely covered by solid blocks will be hidden. Ores exposed to air in caves or water from a lake will not be hidden. With engine-mode: 2, fake ores obstruct the view of real blocks. engine-mode: 3 can reduce network load when joining by a factor of ~2 and helps with chunk packet compression.

Anti-Xray Bypasses

Seed Reversing: Another attack vector is the deterministic nature of Minecraft's world generation. If the client is able to obtain the world seed, it is able to know the real location of every generated ore, completely bypassing Anti-Xray.

Ores Exposed to Air: In engine-mode: 1, engine-mode: 2 and engine-mode: 3, it is possible for a client to view ores that are exposed to air.

Recommended configuration

The recommended configuration for engine-mode: 1, engine-mode: 2 and engine-mode: 3 is as follows:

engine-mode: 1

Default World Configuration 
"overworld": {
    "Enable": true,
    "EngineMode": 1,
    "UpdateRadius": 2.0,
    "MaxBlockHeight": 64,
    "HiddenBlocks": [
        "minecraft:coal_ore",
        "minecraft:deepslate_coal_ore",
        "minecraft:copper_ore",
        "minecraft:raw_copper_block",
        "minecraft:deepslate_copper_ore",
        "minecraft:diamond_ore",
        "minecraft:deepslate_diamond_ore",
        "minecraft:emerald_ore",
        "minecraft:deepslate_emerald_ore",
        "minecraft:gold_ore",
        "minecraft:deepslate_gold_ore",
        "minecraft:iron_ore",
        "minecraft:raw_iron_block",
        "minecraft:deepslate_iron_ore",
        "minecraft:lapis_ore",
        "minecraft:deepslate_lapis_ore",
        "minecraft:redstone_ore",
        "minecraft:deepslate_redstone_ore",
    ],
    "ReplacementBlocks": [
        "minecraft:stone",
        "minecraft:deepslate"
    ],
    "SolidBlocks": [
        "minecraft:calcite",
        "minecraft:oak_planks",
        "minecraft:tuff",
        "minecraft:amethyst_block",
        "minecraft:andesite",
        "minecraft:budding_amethyst",
        "minecraft:gravel",
        "minecraft:deepslate",
        "minecraft:diorite",
        "minecraft:smooth_basalt",
        "minecraft:dirt",
        "minecraft:stone",
        "minecraft:granite"
    ]
}
Nether Configuration 
"nether": {
    "Enable": true,
    "EngineMode": 1,
    "UpdateRadius": 2.0,
    "MaxBlockHeight": 128,
    "HiddenBlocks": [
        "minecraft:ancient_debris",
        "minecraft:nether_gold_ore",
        "minecraft:quartz_ore"
    ],
    "ReplacementBlocks": [
        "minecraft:netherrack"
    ],
    "SolidBlocks": [
        "minecraft:netherrack",
        "minecraft:magma",
        "minecraft:blackstone",
        "minecraft:basalt",
        "minecraft:crimson_nylium",
        "minecraft:warped_nylium",
        "minecraft:gravel"
    ]
}

engine-mode: 2 and engine-mode: 3

Default World Configuration 
"overworld": {
    "Enable": true,
    "EngineMode": 2,
    "UpdateRadius": 2.0,
    "MaxBlockHeight": 64,
    "HiddenBlocks": [
        "minecraft:copper_ore",
        "minecraft:raw_copper_block",
        "minecraft:deepslate_copper_ore",
        "minecraft:diamond_ore",
        "minecraft:deepslate_diamond_ore",
        "minecraft:gold_ore",
        "minecraft:deepslate_gold_ore",
        "minecraft:iron_ore",
        "minecraft:raw_iron_block",
        "minecraft:deepslate_iron_ore",
        "minecraft:lapis_ore",
        "minecraft:deepslate_lapis_ore",
        "minecraft:redstone_ore",
        "minecraft:deepslate_redstone_ore",
        "minecraft:coal_ore",
        "minecraft:deepslate_coal_ore"
    ],
    "ReplacementBlocks": [
        "minecraft:diamond_ore",
        "minecraft:deepslate_diamond_ore",
        "minecraft:emerald_ore",
        "minecraft:deepslate_emerald_ore",
        "minecraft:coal_ore",
        "minecraft:deepslate_coal_ore",
        "minecraft:iron_ore",
        "minecraft:raw_iron_block",
        "minecraft:deepslate_iron_ore",
        "minecraft:amethyst_block",
        "minecraft:andesite",
        "minecraft:budding_amethyst",
        "minecraft:calcite",
        "minecraft:deepslate",
        "minecraft:diorite",
        "minecraft:dirt",
        "minecraft:granite",
        "minecraft:gravel",
        "minecraft:oak_planks",
        "minecraft:smooth_basalt",
        "minecraft:stone",
        "minecraft:tuff"
    ],
    "SolidBlocks": []
}
Nether Configuration 
"nether": {
    "Enable": true,
    "EngineMode": 3,
    "UpdateRadius": 2.0,
    "MaxBlockHeight": 128,
    "HiddenBlocks": [
        "minecraft:basalt",
        "minecraft:blackstone",
        "minecraft:gravel",
        "minecraft:soul_soil",
        "minecraft:netherrack",
        "minecraft:soul_sand"
    ],
    "ReplacementBlocks": [
        "minecraft:ancient_debris",
        "minecraft:glowstone",
        "minecraft:bone_block",
        "minecraft:quartz_ore",
        "minecraft:magma_block",
        "minecraft:nether_bricks",
        "minecraft:nether_gold_ore",
        "minecraft:polished_blackstone_bricks"
    ],
    "SolidBlocks": []
}

FAQ, common pitfalls and support

I can still see (some) ores / use X-ray

As described above, there are several reasons why you might still see (some) ores even though you have enabled Anti-Xray:

  • The ores are above the configured max-block-height value.
  • Anti-Xray cannot hide ores exposed to air or other transparent blocks (in caves for example). In principle this is also the case for engine-mode: 2 and engine-mode: 3, however, usually the fake ores obstruct the view of real blocks. Hiding those exposed ores too requires additional plugins.
  • The block type is missing in the configured block lists. This can be the result of using an outdated configuration file.
I have added fake blocks but X-ray doesn't show them

If you use engine-mode: 2 or engine-mode: 3 and you have added fake blocks to the hidden-blocks list but you can't see them in-game using X-ray, this can have the following reasons:

  • The added block types are tile entities. Anti-Xray can hide (replace) tile entities (such as chests), provided that they are not exposed to air or other transparent blocks. However, Anti-Xray can't place tile entities as fake blocks into the chunk.
  • The block is disabled in your client's X-ray mod or not shown by your X-ray resource pack.
It doesn't work below y = 0 or in certain other places.
  • Your configuration file is probably outdated and missing important blocks in the replacement-blocks list, such as deepslate or biome-specific blocks, such as basalt. You might also want to check if the hidden-blocks list includes all important ores and their deepslate variants.
  • If it doesn't work above a certain y-level, check your max-block-height setting.

inside Obfuscate engine

Obfuscate engine outline
  • The following code outlines the processing flow of the ObfuscateEngine. If you have any questions about the details, please refer to the code below.
var checkOffset = {
    {1,  0,  0 },
    {-1, 0,  0 },
    {0,  1,  0 },
    {0,  -1, 0 },
    {0,  0,  1 },
    {0,  0,  -1}
};

// Engine Mode 1 refers to clear mode
// replaces specified blocks (hidden-blocks) with other "fake" blocks, stone (deepslate at y < 0), netherrack, or
// end_stone based on the dimension.
// fake blocks for dimensions are ReplacementBlocks[0] for y>=0 and [1] for y<0
void Engine::Engine_Mode_1() {
    var ReplacementBlocks = config.ReplacementBlocks;
    var HiddenBlockSet    = config.HiddenBlocks;                      // SL_OBFS | SL_SOLID
    var SolidBlocks       = config.SolidBlocks + config.HiddenBlocks; // SL_SOLID

    var minHeight = (Chunk->getHeightRange().first << 4) + 1;
    var maxHeight = (DimensionData->config->MaxBlockHeight - 1);

    for (var x = 0; x < 16; x++) {
        for (var z = 0; z < 16; z++) {
            for (var y = minHeight; y < maxHeight; y++) {
                bool hide = Solid->at(x, y, z) & SL_OBFS;
                for (auto& [dx, dy, dz] : checkOffset) {
                    hide = hide && (Solid->at(x + dx, y + dy, z + dz) & SL_SOLID);
                    if (!hide) break;
                }
                if (hide) Chunk->setBlock(x, y, z, ReplacementBlocks[y < 0]);
            }
        }
    }
}

// engine-mode: 2 will replace both hidden-blocks and replacement-blocks with randomly generated hidden-blocks
void Engine::Engine_Mode_2() {
    var ReplacementBlocks = config.ReplacementBlocks;
    var HiddenBlockSet    = config.HiddenBlocks + config.ReplacementBlocks;                      // SL_OBFS | SL_SOLID
    var SolidBlocks       = config.SolidBlocks + config.HiddenBlocks + config.ReplacementBlocks; // SL_SOLID

    var minHeight = (Chunk->getHeightRange().first << 4) + 1;
    var maxHeight = (DimensionData->config->MaxBlockHeight - 1);

    for (var x = 0; x < 16; x++) {
        for (var z = 0; z < 16; z++) {
            for (var y = minHeight; y < maxHeight; y++) {
                bool hide = Solid->at(x, y, z) & SL_OBFS;
                for (auto& [dx, dy, dz] : checkOffset) {
                    hide = hide && (Solid->at(x + dx, y + dy, z + dz) & SL_SOLID);
                    if (!hide) break;
                }
                var randomBlock = ReplacementBlocks[rand()];
                if (hide) Chunk->setBlock(x, y, z, randomBlock);
            }
        }
    }
}

// engine-mode: 3 works similarly to engine-mode: 2, but instead of randomizing every block, it randomizes the block for
// each layer of a chunk.
void Engine::Engine_Mode_3() {
    var ReplacementBlocks = config.ReplacementBlocks;
    var HiddenBlockSet    = config.HiddenBlocks + config.ReplacementBlocks;                      // SL_OBFS | SL_SOLID
    var SolidBlocks       = config.SolidBlocks + config.HiddenBlocks + config.ReplacementBlocks; // SL_SOLID

    var minHeight = (Chunk->getHeightRange().first << 4) + 1;
    var maxHeight = (DimensionData->config->MaxBlockHeight - 1);

    for (var y = minHeight; y < maxHeight; y++) {
        var randomBlock = ReplacementBlocks[rand()];
        for (var x = 0; x < 16; x++) {
            for (var z = 0; z < 16; z++) {
                bool hide = Solid->at(x, y, z) & SL_OBFS;
                for (auto& [dx, dy, dz] : checkOffset) {
                    hide = hide && (Solid->at(x + dx, y + dy, z + dz) & SL_SOLID);
                    if (!hide) break;
                }
                if (hide) Chunk->setBlock(x, y, z, randomBlock);
            }
        }
    }
}

Footnotes

  1. Image design by Oberfail, initially posted in the PaperMC Discord. ↩