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	write a portable .mcmat below the write root
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 identifier, display label and screen position, fps, toasts
ui.menu.list / ui.menu.invoke {id}	app	the menu catalog; behave like a click
ui.panel.maximize {panel}	app	maximize an open, active panel: Graph, Explorer, Library, View3d, View2d, Properties, Console, or History; restore with ui.menu.invoke {"id":"ui.unmaximize"}
ui.set {...}	app	recursively 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.

ui.inspect.maximizedPanel reports the temporary maximized panel, or null. Maximizing preserves the saved workspace. Shift+Space toggles maximization under the pointer; text inputs, popups, modal dialogs and pointer drags retain their input.

Key commands

Command	Params
file.new	{kind?, template?, name?, size?, width?, height?}; material width/height override size per axis (default 1024 px), rounded down to powers of two in 16..8192; creation is one undo step. Templates from graph.templates: empty, pbr, atomics
graph.node.edit	{} resolves the selected FX-Map, processor or local graph instance to {kind, node, parameter?, graph?}; use ui.menu.invoke to enter it in the graph panel
graph.pattern.set	{id, pattern} replaces an FX-Map subgraph with cycle validation and undo
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}} (with bind, id may be omitted: the input is named after the parameter, opacity, opacity_1…) / {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

3D material assignment

view.3d.outputs {graph?, reset?} applies a material graph's image outputs by their usage. graph accepts an index or name and defaults to the open graph. Ordinary application preserves unmatched channel assignments; reset: true clears them while preserving the scene, camera and lighting. Outputs with unsupported usages or scalar/vector results cannot supply material textures.

view.3d.assign {graph?, node?, port?, channel, reset?} assigns an individual image to baseColor, normal, roughness, metallic, height, ambientOcclusion, emissive or opacity. The node defaults to the selection only in the open graph. The port accepts an identifier or index; terminal Output nodes use output or index 0. Assignments refer to their source graph and named port, update when that source changes, and remain active while editing a Function Graph. view.3d.clear {} removes assignments without resetting the scene.

Opening a material graph automatically previews its output usages. Selecting or previewing a node in 2D does not reassign the 3D material. Dragging a graph from Explorer onto the 3D view applies its outputs without opening the graph. Canvas and Explorer context menus use the same assignment commands; the 3D View's Material menu lists its channel sources. A Height-only output affects height sampling, not Base Color; assign that image to baseColor to inspect its grayscale pattern on the mesh.

session.inspect.material3d reports assignments and resolved channels, including source graph/node/port, image dimensions and mean values. Assignment commands leave the package and document undo history unchanged. Document undo restores the associated source references; replacing a package clears them.

Function graphs

file.new {"kind": "function", "name": "Calculation"} creates a standalone Function Graph. Omit kind, or use "material", for a Graph. graph.function.set {"function": {...}} replaces the active standalone function through one validated, undoable command. Both graph.function.set and graph.function.edit accept an optional target: {"kind":"graph"} (the default), {"kind":"parameter","node":12,"parameter":"function"}, {"kind":"dynamic","node":12,"parameter":"opacity"}, or {"kind":"pattern","owner":12,"node":3,"parameter":"patternrotation"}.

graph.function.edit accepts edit: {action: add|move|connect|value|output, ...}. For example, {"edit":{"action":"add","operation":"mul","at":[256,0],"snap":true}} creates and returns a node ID using the same defaults as library and context-menu insertion. graph.pattern.edit accepts the FX-Map owner id and edit: {action: add|move|connect|disconnect|root|value, ...}. Use command.list for command descriptions and the serialized FunctionEdit/PatternEdit types in crates/engine/src/ for the action fields. Value edits are individual undo steps by default; merge: true groups repeated updates to the same target and value until edit.finish or another edit ends the group. Idle UI frames preserve explicitly requested automation groups.

ui.menu.invoke sends selection actions to the focused editor, including embedded Function windows. ui.inspect.subgraph.target identifies that Function target; its canvas rectangles and ports correspond to the same editor. Raw command.run calls retain their explicit command targets.

Selection and clipboard commands (graph.select, edit.selectAll, edit.copy, edit.cut, edit.paste, edit.duplicate, edit.delete, their without-link/relink variants and upstream/downstream selection) also work without a UI. They infer the active standalone Function Graph. To address an embedded graph, pass function: <FunctionGraphTarget> or pattern: <owner node id> and explicit ids for selection-dependent operations. edit.selectAll returns those IDs. An optional numeric graph guards against the owning graph no longer being active. graph.align accepts the same Function and FX-Map targets with explicit IDs.

Results include ids and selected; copy/cut also return copied and a typed clip accepted by paste. The session retains the most recent embedded clipboard. Cross-target paste keeps internal links and drops external links. Standalone commands update the session selection; embedded commands return their selection without changing the parent selection. Invalid operations preserve the document, clipboard, selection and undo history. Creation and all function/pattern setters share cycle, capacity, ID and position validation.

A function has nodes and an optional output node id. Each node has id, native op, inputs (source ids or null for unwired ports), optional value, type_code and pos. For example, const_float1 supplies a scalar and mul multiplies its a and b inputs. The catalog in crates/nodes/src/function/catalog.rs defines all native operation and port ids. Processors and dynamic parameters use the same function representation. Graph validation and execution use bounded iterative traversal and reject cycles.

graph.annotation.select {"kind": "frame"|"comment", "id": ...} selects an annotation. graph.frame.edit accepts title, titleVisible, description, color and rect. graph.frame.move {"id": ..., "by": [dx, dy], "snapToGrid": true} moves enclosed nodes, comments, nested frames and pins together. graph.comment.edit accepts text, at and size. session.inspect includes annotation selection and the standalone function; ui.inspect includes frame and comment rectangles for synthetic input.

Portable materials (TextureCraft)

A .mcmat portable material is a zip: material.json (manifest), maps/<usage>.png and source.sbs (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": 2, "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.sbs" }

• Usages come from the shared ComponentUsage catalog (the first output of each, excluding any). The catalog includes PBR, diffuse/specular, coat, sheen, scattering and user channels. Color maps are 8-bit sRGB PNGs; data maps are 16-bit linear. Each map records its color space. Additional usage identifiers do not change the manifest version; consumers may ignore usages they do not support. Normals are tangent space, OpenGL (Y+); height is 0..1 with 0.5 at the surface. The 3D preview supports base color (including diffuse), normal, roughness, metallic, height, ambient occlusion, emissive and opacity; other usages remain available for SBS and exports.
• 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 require manifest version 2.

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.sbs 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
file.open	opens native .sbs 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?}: native SBS; .sbs is appended when the path does not end in .sbs

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.

While an FX-Map subgraph is open, ui.inspect.subgraph identifies its owner and selection. Canvas node IDs and ports refer to that embedded graph. ui.menu.invoke with ui.graph.parent returns to the parent canvas.

Automation command requests each form a separate undo step. Embedded graph edits may explicitly pass merge: true to continue one gesture; an ordinary request ends that merge. UI slider gestures still coalesce until release. material_export uses the headless write-root capability and does not expose unrestricted engine file paths.

Bitmap Color space selects sRGB or Linear. graph.input.bind accepts linear: true for normal, height and other data maps. Input preview bindings persist in native SBS graph options with the materialcraft.previewImage. and materialcraft.previewLinear. prefixes; these options describe MaterialCraft editor previews and do not establish external application interoperability.