materialcraft/docs/control-protocol.md

Control protocol and MCP

Last reviewed: 2026-11-02 · Last updated: 2026-11-03 · Change: minor (material_export MCP tool) · Target: the professional node-based material workflow

Agents drive MaterialCraft three ways, all dispatching the same engine commands:

1. MCP (materialcraft-cli mcp): headless (an in-process session, files only below --read-root / --write-root, also spelled --automation-read-root / --automation-write-root as in the other crafting apps; serve takes them too) or bridged to the running app (--bridge <port>).
2. JSON lines (materialcraft-cli serve): the same methods on stdio, or on 127.0.0.1:<port> behind a token.
3. The app's control channel (materialcraft --control <port>): one JSON request per line, {"id", "method", "params"} → {"id", "ok": true, "result"} or {"id", "ok": false, "error"}. The first request must be {"method":"auth","params":{"token":"…"}} with the token from MATERIALCRAFT_CONTROL_TOKEN (16 to 1024 printable ASCII characters) or the file <temp>/materialcraft-control-<port>.token, a fresh random 256-bit token written after the port is bound. On Unix the file is created new with mode 0600 (owner only); if an existing file there cannot be replaced, the control server stays off and MATERIALCRAFT_CONTROL_TOKEN is the alternative. Clients (materialcraft-cli mcp --bridge) refuse a token file that is a symlink, not a regular file, not owned by them, or accessible to group or others. A connection gets one authentication attempt, within 10 s; a wrong token, any other first request or malformed JSON closes it. At most 16 connections are served at once. Whoever holds the token has full engine-command authority, including host file access. Set MATERIALCRAFT_NO_PREFS=1 for scripted runs so the user's layout is left alone.

Methods

Method	Where	What
ping	all	"pong"
command.list {filter?}	all	every command: id, label, menu, shortcut, params doc, enabled
command.run {id, params?}	all	run one command (programmatic: never opens a dialog)
command.batch {steps}	headless	run [{id, params}] in order, stop at the first error
session.inspect	all	package, graphs, the open graph's nodes (def, params, bindings, base, ports, cook error/size/mean/ms), wires, frames, comments, pins, exposed inputs, views, history
package.open {path} / package.save {path?}	headless	workspace-scoped package I/O
bitmap.import {path, name?}	headless	embed an image as a resource
outputs.export {dir, format?, pattern?, depth?, size?, graph?}	headless	cook at full size and write every output
material.export {path, graph?, size?, values?}	headless	cook and write a portable .mcmat (.mcmat appended when missing) below the write root: the workspace-scoped file.exportMaterial
render {view?, width?, height?, yaw?, pitch?, scene?, node?, port?, full?, tiling?, hq?, displacement?}	headless	PNG (base64) of the 3D view or of one node; hq is the beauty render (displaced mesh, ray-traced AO, shadowed key light, 3×3 supersampling), displacement its depth in scene radii
ui.inspect	app	UI state, the graph view rectangle, every node's screen rectangle, every port's screen position, fps, toasts
ui.menu.list / ui.menu.invoke {id}	app	the menu catalog; behave like a click
ui.set {...}	app	merge fields into the UI state
ui.input {events}	app	synthetic input, below
view.screenshot {view?: "3d"|"2d"}	app	PNG of the 3D or 2D view
ui.screenshot	app	PNG of the whole window
ui.resize {width, height}	app	window size in points

Synthetic input (ui.input)

Events are applied one frame at a time, so egui sees real presses, drags and releases. Positions are window points (take them from ui.inspect's nodes and ports).

{"method": "ui.input", "params": {"events": [
  {"type": "drag", "from": [512, 140], "to": [600, 220], "steps": 12},
  {"type": "click", "pos": [700, 300], "button": "left", "modifiers": ["ctrl"]},
  {"type": "doubleClick", "pos": [640, 180]},
  {"type": "scroll", "pos": [640, 300], "delta": [0, -120]},
  {"type": "key", "key": "Space"},
  {"type": "text", "text": "perlin"},
  {"type": "key", "key": "Enter"}
]}}

Types: move, down, up, click, doubleClick, drag, scroll, key (egui key names: A, Enter, Space, Delete, F5, …), text. Buttons: left, right, middle.

Key commands

Command	Params
file.new	{template?, name?, size?}; templates from graph.templates (empty, pbr, bricks, stone_tiles, wood, rusty_metal, fabric, ground)
graph.node.add	{def, at?, params?, connectFrom?: {node, port?}, label?}
graph.connect / graph.disconnect	{from, fromPort?, to, toPort?} / {to, toPort}
graph.wire.insertDot	{to, toPort, at?}: split the wire feeding to.toPort with a reroute Dot node at at (graph point, default midway), selected
graph.wire.swap / graph.wire.delete	{wires: [{to, toPort}, ...]}: swap (two) or reverse (more, in input order) where the wires come from / delete them, one undo step each
graph.node.param	{id?, param, value}: numbers, [x, y], "#rrggbb", enum index, curve [[x, y], …], gradient [[pos, color], …], or a typed value {"t": "function", "v": {...}}
graph.node.base	{id?, sizeMode?, size?, format?, seed?, tiling?}
graph.exposed.add / graph.exposed.set	{id, label?, default?, bind?: {node, param}} / {id, value}
graph.node.function	{id?, param, function} drives a parameter by a function graph of the graph's inputs (dynamic parameter); {id?, param, remove: true} removes it
graph.preset.save / .apply / .delete	{name}: store, restore or remove the current input values
graph.createFromSelection	{name?, ids?}: move nodes into a sub-graph and replace them with an instance
view.2d / view.3d	which node the 2D view shows, channel, tiling, histogram; scene, environment, camera, tiling, heightScale (how far the height output raises the mesh, in mesh radii) and heightLevel (the height that stays on the surface; 0 = the relief rises out of it), normalYFlip (interpret DirectX normal maps; default false/OpenGL), transparency (see through where the alpha is below one: the opacity output, else the base color's alpha), alphaView (show the alpha channel)
view.3d.loadMesh	{path} shows an OBJ, glTF or GLB mesh (scene custom)
library.list	{filter?, category?}: every node with ports and parameters

Function graphs

Pixel and value processors carry a function parameter: {"nodes": [{"id", "op", "inputs": [ids], "value"?}], "output": id}. Ops: constants (const_float, const_float2/3/4, const_int, const_bool), variables (get_pos = normalized pixel position, get_size, get_var with value = an exposed input id), samplers (sample_gray, sample_color with value = input index 0–3, input = a float2 position), vectors (vec2/3/4, swizzle with value = "xy" etc.), casts, arithmetic (add sub mul div mod neg dot), logic and comparison (and or not gt ge lt le eq ne), functions (abs floor ceil frac sqrt exp log sin cos tan atan2 pow min max clamp lerp length normalize rand noise) and if_else. Values are 4-wide; scalars broadcast.

Portable materials (TextureCraft)

A .mcmat portable material is a zip: material.json (manifest), maps/<usage>.png and source.mcraft (the package). TextureCraft applies it as a fill layer and keeps the exposed inputs editable, re-cooking through materialcraft-cli. The format is a convention the two apps share; each has its own reader and writer (crates/formats/src/material.rs here), so keep them in step.

{ "format": "craft-material", "version": 1, "name": "Brick wall", "graph": "Brick_wall", "size": [2048, 2048],
  "maps": [{"usage": "baseColor", "file": "maps/baseColor.png", "colorSpace": "srgb"}],
  "parameters": [{"id": "wear", "label": "Wear", "default": {"t": "float", "v": 0.5}, "min": 0, "max": 1,
                  "value": {"t": "float", "v": 0.8}}],
  "inputs": [{"identifier": "curvature", "kind": "gray"}],
  "presets": [{"name": "Worn", "values": {"wear": {"t": "float", "v": 1.0}}}],
  "source": "source.mcraft" }

• Usages: baseColor, normal, roughness, metallic, height, ambientOcclusion, emissive, opacity, specular (the first output of each). Color usages (baseColor, emissive, specular) are 8-bit sRGB PNGs, the rest 16-bit linear. Normals are tangent space, OpenGL (Y+); height is 0..1 with 0.5 at the surface.
• Parameters are the exposed inputs other apps can set (float, float2-4, int, int2, bool, color, enum), values in the typed form {"t", "v"}; colors are linear RGBA.
• Inputs are the graph's input nodes. Mesh maps feed them by identifier: ambientOcclusion, curvature, thickness, position, worldNormal, normal, height, id, bentNormal, opacity, colorMap, worldDirection.
• Readers ignore unknown fields and refuse a version newer than they know.

Command	Params
file.exportMaterial	{path, graph?, size? (px), values? {input: value}, inputs? {identifier: image path}}: cook and write a .mcmat. TextureCraft runs materialcraft-cli run source.mcraft file.exportMaterial {...} to re-cook at its texture set's resolution with its own values and baked mesh maps
file.sendToTextureCraft	{graph?}: export into TextureCraft's library folder (Documents/TextureCraft/library), where its shelf lists it
graph.input.bind / graph.input.unbind	{identifier, resource? | path?, linear?} / {identifier}: a preview image for an input node (a mesh map exported from TextureCraft), saved in the package; linear: true preserves data-map values without sRGB conversion
file.open	opens .sbs (by content) and .mcraft packages, and a .mcmat's source package, on its graph, with no file name. Returns warnings: what an SBS file holds that MaterialCraft can't read yet (missing nodes are kept as placeholders); also in session.inspect as package.warnings
file.save	{path?}: SBS unless the file is .mcraft; .sbs is appended when path has no package extension

MCP tools

session_inspect, command_list, command_run, command_batch, library_list, graph_new, node_add, node_connect, node_param, package_open, package_save, bitmap_import, outputs_export, material_export, view_render (headless) and, bridged to the app, view_screenshot, ui_screenshot, ui_inspect, ui_menu_invoke, ui_input. package_open opens .mcmat files too, and material_export {path, graph?, size?, values?} writes one below --write-root (path is relative, the parent folder must exist, values are exposed input values). The workspace sandbox still refuses file.* commands, so a sandboxed agent exports through the tool, not file.exportMaterial; mesh-map inputs stay a CLI feature.