LLM Material

DSL-driven Material asset generation for Unreal Engine 5. The agent writes .llmmat JSON, the editor turns it into a real UMaterial — full expression graph, UE5 Substrate, and inline HLSL .ush shader functions.

Skill file: skills/llm-material/SKILL.md

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When the Agent Loads It

The agent loads this skill when the user asks to:

• Create or design a UE5 Material (surface, translucent, emissive, decal, post-process)
• Convert a material description into a .llmmat file
• Inspect or modify an existing .llmmat file
• Look up an Expression node (Add, Multiply, TextureSample, Custom, etc.)
• Write an HLSL shader function (.ush) and reference it from a material

Triggers: .llmmat, Material, expression graph, Substrate, HLSL, .ush, Custom node, MaterialExpression.

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Prerequisites

Requirement	Notes
UE 5.7+	Engine version
LLM Material plugin	Install from Fab or copy from this repo to Plugins/
Enabled in editor	Edit → Plugins → AI → LLM Material → restart editor

For Substrate materials, the project must have Substrate enabled in project settings. The skill body covers both legacy and Substrate paths.

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Quick Example

Ask the agent:

"Give me an emissive cyan material with a pulsing Fresnel glow."

The agent produces a .llmmat file:

{
  "version": "1.0",
  "name": "FresnelPulse",
  "domain": "Surface",
  "blendMode": "Opaque",
  "shadingModel": "DefaultLit",
  "functions": [
    {
      "name": "PulseWave",
      "returnType": "float",
      "parameters": [
        { "name": "Time",  "type": "float" },
        { "name": "Speed", "type": "float", "defaultValue": "2.0" }
      ],
      "body": "return 0.5 + 0.5 * sin(Time * Speed);"
    }
  ],
  "nodes": [
    { "id": "time",  "type": "Time",                "properties": {} },
    { "id": "pulse", "type": "Custom",
      "properties": { "OutputType": "CMOT Float 1", "Code": "return PulseWave(Time, 2.0);" } },
    { "id": "fresnel", "type": "Fresnel",           "properties": { "Exponent": 3.0 } },
    { "id": "mult",    "type": "Multiply",
      "properties": { "A": { "node": "pulse" }, "B": { "node": "fresnel" } } },
    { "id": "cyan",    "type": "Constant3Vector",   "properties": { "Constant": [0.0, 1.0, 1.0] } },
    { "id": "emissive", "type": "Multiply",
      "properties": { "A": { "node": "cyan" }, "B": { "node": "mult" } } }
  ],
  "output": {
    "emissiveColor": { "node": "emissive", "pin": "Result" }
  }
}

Save it, open the LLM Material panel, click Generate — the FresnelPulse material appears.

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What the Skill Knows

The full skill body contains:

• All expression node types — Add, Multiply, TextureSample, Constant3Vector, Lerp, Fresnel, Time, Panner, Custom, etc. The agent reads the schema at Plugins/LLMMaterial/Content/MaterialExpressionSchema.json for the canonical list.
• Connection rules — which inputs accept which output types, when the agent needs an explicit Custom node, etc.
• Output pins — baseColor, metallic, roughness, normal, emissive, opacity, worldPositionOffset, etc.
• Substrate — modern UE5 material architecture (slab + node + sub-node model). The skill covers both legacy and Substrate authoring.
• USH (HLSL functions) — functions[] blocks generate .ush files; ushIncludes[] references existing ones; Custom nodes with HeaderRef call into them.
• Examples — full reference examples in Plugins/LLMMaterial/Content/Examples/.

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Compiling the JSON into an Asset

# Manual: editor panel
Tools → LLM Material Panel → select .llmmat file → Generate

# CLI (with llm-easy-shell installed)
material generate /Game/Materials/FresnelPulse --from FresnelPulse.llmmat

The generated Material asset opens in the Material Editor for further tuning.

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Round-Trip

Already have a Material you want to author against? Use the editor panel's Export Material button to dump the current state to a .llmmat file. The agent edits the file, you re-generate.

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Related Skills

• llm-easy-shell → — drive the editor from the CLI.
• llm-easy-shell-lite → — read-only exploration: "what shader does this material use?"