threenative-sculpt-mcp

Five fail-closed MCP tools for turning a reference image into user-owned procedural Three.js source. The server evaluates plans, ObjectSculptSpec depth, captured frames, and pass gates; it never generates source or launches a browser.

Run locally

pnpm install --frozen-lockfile
pnpm build
node dist/server.js

The server communicates over stdio. Configure an MCP host to launch ./node_modules/.bin/threenative-sculpt-mcp from the generated project.

Related MCP server: openscad-mcp

Surface

• sculpt_plan — validate a reference and return the locked pass order plus relevant grimoire URIs.

• sculpt_spec_gate — validate the retained ObjectSculptSpec contract and depth minimums.

• sculpt_compare — compare an existing capture with the reference globally and by normalized region.

• sculpt_pass_gate — return advance, retry, or stop; uncertainty can never advance.

• sculpt_grimoire — read a topic; unknown topics fail with the complete valid-topic list.

Every technique-safe page is exposed as sculpt://grimoire/<topic>.

The source repository retains the complete upstream grimoire verbatim. The served resource index is narrower: pages containing concrete fenced GLSL or material recipes are rejected by both resource discovery and sculpt_grimoire. This keeps the MCP surface technique-oriented; the agent authors the game's materials and shaders in src/render/.

Upstream does not contain a standalone JSON Schema for ObjectSculptSpec. This fork documents its explicit MCP runtime subset in schema/object-sculpt-spec.runtime.schema.json and applies the upstream simple/moderate/complex/ultra-complex depth thresholds in code. The eight locked passes are blockout, structural, form, material, surface, lighting, interaction, and optimization.

The nested shapes consumed by sculpt_spec_gate are objects: the tier is preSpecAssessment.complexity.tier, and inventory entries are in preSpecAssessment.detailInventory.details. This complete simple-tier example is also packaged as examples/simple-object-sculpt-spec.json:

{
  "schemaVersion": "2.1",
  "targetName": "Reference object",
  "suitability": "pass",
  "coordinateFrame": {},
  "silhouette": {},
  "componentTree": [{ "id": "root", "level": "macro", "localFeatures": [] }],
  "materials": [{ "id": "base" }],
  "repetitionSystems": [],
  "proceduralStrategy": ["Build the observed silhouette"],
  "preSpecAssessment": {
    "complexity": { "tier": "simple" },
    "detailInventory": {
      "details": [
        { "id": "primary-outline" },
        { "id": "dominant-proportion" },
        { "id": "material-break" }
      ]
    }
  },
  "qualityContract": {
    "minimumSpecDepth": {
      "macroComponents": 1,
      "mesoComponents": 0,
      "microFeatureGroups": 0,
      "materialLayers": 1,
      "repetitionSystems": 0,
      "reviewViewpoints": 2
    }
  },
  "qualityTargets": { "reviewViewpoints": ["front", "three-quarter"] }
}

Deterministic pixel comparison is diagnostic evidence. sculpt_pass_gate requires a semantic review of the same image pair and its critical features; absent or ambiguous review evidence returns retry (or stop at the configured final attempt), never advance. Low deterministic scores and regional confidence produce correction guidance but do not block an otherwise passing semantic review when compareResult.ambiguous is false. An explicitly ambiguous comparison still blocks advancement.

sculpt_compare reads PNG, JPEG, WebP, GIF, AVIF, and TIFF through Node's sharp package. It rejects missing, zero-byte, undecodable, and all-one-colour captures. It does not include Python, uv, Playwright, browser automation, source generation, or runtime game code.

Verify

pnpm typecheck
pnpm test
pnpm pack --dry-run

The retained material, adaptations, ports, and resource-safety filter are described in NOTICE; the package is Apache-2.0.