3dsmax MCP Dev

3dsmax-mcp Skill Guide

Principles:

• Prefer dedicated tools over raw MAXScript
• Prefer SDK introspection over MAXScript reflection
• Do NOT render unless asked — but capture_multi_view (quad view) is encouraged after building or modifying scenes so the user can see the result

1. Deep SDK Introspection (Use First)

When encountering an unfamiliar class, plugin, or object — use C++ SDK introspection first. These read the DLL class registry directly. Faster and more complete than MAXScript's showClass/getPropNames.

Tool hierarchy:

1. introspect_class — Full API of any class: ParamBlock2 params (names, types, defaults, ranges), FPInterface functions/properties. Works on any class. Blocked for OSLMap — use introspect_osl instead.
2. introspect_instance — Same but on a live object with current values + modifier stack + material params. Add include_subanims:true for animation tree.
3. introspect_osl — Lightweight reflection for OSLMap and any material/texturemap class. Creates a temp instance, dumps properties with types, interfaces, and output channels. For OSLMap, use osl_file param to load a shader (e.g. osl_file:"UberBitmap2"). Short names resolve to (getDir #maxRoot)/OSL/<name>.osl.
4. discover_plugin_classes — Enumerate ALL classes from DLL directory. Filter by superclass or name pattern.

Always prefer these over MAXScript reflection:

• introspect_class > inspect_plugin_class (gets defaults, ranges, function signatures)
• introspect_osl for OSLMap and scripted material/map classes (bounded output, handles dynamic params)
• introspect_instance > inspect_properties for plugin objects (catches params getPropNames misses)
• discover_plugin_classes > list_plugin_classes (scans every loaded DLL)

Unknown plugin workflow:

1. discover_plugin_classes pattern:"*Forest*"     → find classes
2. introspect_class class_name:"Forest_Pro"        → get full API
3. introspect_instance name:"ForestPack001"        → read live values
4. Proceed with edits — you now know every param, type, range, value

Material/shader introspection:

• introspect_instance reads the entire material tree in one call — every param, every texmap slot, all sub-materials with current values
• Use for renderer conversion workflows: read source material tree → map params → write to new material

Deep SDK learning tools:

These tools let you understand how 3ds Max works at the deepest level — class relationships, real-world usage patterns, reference graphs, and live events.

1. learn_scene_patterns — Analyze the current scene in one call. Returns frequency-sorted data on:

   • Which geometry/material/modifier/texmap classes are used and how often
   • Common modifier stacks (e.g. "TurboSmooth | Skin | Skin Wrap" = character deform pipeline)
   • Material-to-geometry associations (e.g. "Shell Material → PolyMeshObject" = export pipeline)
   • Texture-to-material connections (e.g. "Bitmap → Physical Material")
   • Use first when opening an unfamiliar scene — instantly understand the entire production setup

2. walk_references — Walk the SDK reference graph from any object. Shows how materials, modifiers, controllers, and textures connect through Max's reference system.

   • Use to understand shader networks: "this Shell Material references Standard Surface + Physical Material"
   • Use to debug why changing one object affects another
   • max_depth controls detail (default 4, max 8)

3. map_class_relationships — Scan DLL directory to find which classes accept which reference types via ParamBlock2 params.

   • Shows "Physical Material accepts texturemaps in these slots: base_color_map, bump_map, ..."
   • Shows "Forest_Pro accepts nodes + texturemaps"
   • Filter by superclass or name pattern
   • Use before wiring — know which slots exist without guessing

4. watch_scene — Live event streaming from 3ds Max. Registers native SDK callbacks for:

   • node created/deleted, selection changes, modifier added
   • material assigned, file open, undo/redo, render start/end
   • Actions: start, stop, get (poll events), clear, status
   • Use since=<timestamp> for incremental polling
   • Use during iterative work — track what the user does between your calls

Learning workflow for new scenes:

1. learn_scene_patterns                           → understand the whole scene
2. walk_references name:"MainCharacter"           → map one object's dependencies
3. introspect_instance name:"MainCharacter"       → get live param values
4. map_class_relationships superclass:"material"  → learn what plugs into what
5. Now you understand the scene deeply — proceed with edits

2. Plugin & Tool Development (SDK Learning)

When the user is developing a tool, plugin, or automating a workflow and you need to understand SDK classes, parameters, or how things connect — use native introspection, not documentation or guesswork.

Learning an unknown class or API:

1. discover_plugin_classes pattern:"*ClassName*"   → find it in the DLL registry
2. introspect_class class_name:"ClassName"          → get ALL params, types, defaults, ranges, functions
3. map_class_relationships pattern:"ClassName"      → see what it accepts (nodes, materials, texmaps)

NOTE: Arnold materials (ai_standard_surface, etc.) are scripted plugins — discover_plugin_classes and introspect_class won't find them. Create via MAXScript: ai_standard_surface(). Use inspect_plugin_class or introspect_osl for reflection instead.

Understanding how a live object works:

1. introspect_instance name:"ObjectName"            → every param with current value
2. walk_references name:"ObjectName"                → full dependency graph (materials → textures → controllers)
3. introspect_instance name:"ObjectName" include_subanims:true → animation/controller tree

Testing changes and verifying results:

1. get_scene_delta capture:true                     → capture baseline
2. (make changes — create objects, assign materials, add modifiers)
3. get_scene_delta                                  → see exactly what changed (added/removed/modified with before/after values)

Reverse-engineering a production scene:

1. learn_scene_patterns                             → modifier stacks, material combos, class frequencies
2. walk_references name:"KeyObject"                 → map its dependency tree
3. map_class_relationships superclass:"material"    → learn all material slot wiring possibilities

Watching user actions in real-time:

1. watch_scene action:"start"                       → enable event tracking
2. (user works in Max — creates, selects, modifies)
3. watch_scene action:"get"                         → see every action with full detail

Rules:

• NEVER guess parameter names — use introspect_class to get the exact names, types, and ranges
• NEVER assume slot connections — use map_class_relationships to see what plugs into what
• NEVER skip verification — use get_scene_delta after mutations to confirm what actually changed
• When writing MAXScript that targets a specific class, introspect it first to get correct property names
• When building a C++ native handler, use introspect_class to understand the ParamBlock2 layout before writing SetValue calls

3. Default Workflow

1. Context — get_bridge_status, get_scene_snapshot
2. Inspect — introspect_instance (preferred) or inspect_object + get_material_slots
3. Mutate — use a dedicated tool (never execute_maxscript if a tool exists)
4. Verify — get_scene_delta or re-inspect after mutation

4. Scene Organization (Pure C++ SDK)

Layers — manage_layers:

• Actions: list, create, delete, set_current, set_properties, add_objects, select_objects
• Properties: hidden, frozen, renderable, color, boxMode, castShadows, rcvShadows, xRayMtl, backCull, rename, parent

Groups — manage_groups:

• Actions: list, create, ungroup, open, close, attach, detach

Named Selection Sets — manage_selection_sets:

• Actions: list, create, delete, select, replace

5. Tool Reference

Scene reads

get_scene_info get_selection get_scene_snapshot get_selection_snapshot get_scene_delta get_hierarchy

Objects

get_object_properties set_object_property create_object delete_objects transform_object select_objects set_visibility clone_objects set_parent batch_rename_objects

Modifiers

add_modifier remove_modifier set_modifier_state collapse_modifier_stack make_modifier_unique batch_modify

Materials

• Create + assign: assign_material
• Edit: set_material_property, set_material_properties
• Inspect: get_material_slots, get_materials
• Multi/Sub: set_sub_material
• Textures: create_texture_map, set_texture_map_properties, create_material_from_textures
• Shell + ORM: create_shell_material, replace_material, batch_replace_materials
• OSL: write_osl_shader

Known Issues — Material Pipeline

• create_material_from_textures has no ORM packed texture support (OcclusionRoughnessMetallic)
• No UberBitmap (OSLMap) awareness — uses Bitmaptexture/ai_image instead of OSL UberBitmap2.osl
• No MultiOutputChannelTexmapToTexmap knowledge — cannot split R/G/B channels from a single map
• No Shell Material support — cannot wrap glTF + Arnold in dual-pipeline structure
• Arnold wiring uses ai_image instead of UberBitmap — misses channel splitting for packed maps
• AO compositing uses ai_layer_rgba instead of ai_multiply — inconsistent with standard Arnold workflows
• No concept of render vs export material slots (Shell originalMaterial / bakedMaterial)

Viewport

• Fast: capture_viewport
• Multi-angle grid: capture_multi_view (front/right/back/top stitched into one image)
• Fullscreen: capture_screen (requires enabled=True)

External .max files (no scene load)

• inspect_max_file — OLE metadata + optional object names + class directory
• search_max_files — scan folder for objects matching pattern (batched, token-optimized)
• merge_from_file — selective merge with duplicate handling
• batch_file_info — parallel metadata from multiple files

Plugin discovery

• discover_plugin_surface, get_plugin_manifest, refresh_plugin_manifest
• inspect_plugin_class, inspect_plugin_constructor, inspect_plugin_instance
• MCP resources: resource://3dsmax-mcp/plugins/{name}/manifest|guide|recipes|gotchas

tyFlow

• Create: create_tyflow, create_tyflow_preset
• Inspect: get_tyflow_info (enable include_operator_properties for deep readback)
• Edit: modify_tyflow_operator, set_tyflow_shape, set_tyflow_physx, add_tyflow_collision
• Simulate: reset_tyflow_simulation, get_tyflow_particle_count, get_tyflow_particles

Controllers & wiring

• assign_controller, inspect_controller, inspect_track_view
• list_wireable_params, wire_params, get_wired_params, unwire_params

Data Channel

• add_data_channel, inspect_data_channel, set_data_channel_operator, add_dc_script_operator

Scene management

• manage_scene (hold/fetch/reset/save/info)
• get_state_sets, get_camera_sequence

6. When to Use execute_maxscript

Almost never. Only when there is genuinely no dedicated tool:

• Animation keyframing, render/environment settings, custom scripted operations

DO NOT use execute_maxscript for:

• Anything a dedicated tool already does — even if it feels faster to write a script
• Batch operations — call the dedicated tool in a loop, do not write MAXScript for loops
• Setting properties — use set_object_property, not execute_maxscript("$obj.prop = val")
• Creating objects — use create_object, not execute_maxscript("Box()")
• Assigning materials — use assign_material, not MAXScript
• Selecting objects — use select_objects, not execute_maxscript("select $obj")
• Inspecting — use inspect_object/introspect_instance/introspect_osl, not showProperties

If you catch yourself writing MAXScript that a tool already handles, stop and use the tool.

7. MCP Tool Pitfalls

• Fast/small models send "foo" instead of ["foo"] for list params — all tool signatures use coerced types (StrList, FloatList, IntList, DictList from src/coerce.py) that auto-wrap single values into one-element lists. Any new tool with a list[T] param must use these types instead of bare list[].
• get_material_slots with slot_scope:"all" + include_values:true returns 40+ params on complex materials (Physical, Arnold). Prefer slot_scope:"map" (default) unless you need every param.
• assign_controller and set_controller_props params dict values must work as both strings and numbers — the native handler coerces automatically. Small models may send {"seed": 42} (number) or {"seed": "42"} (string); both are valid.
• list_wireable_params returns paths with [#Parameters] grouping level (e.g. [#Object (Box)][#Parameters][#height]). The native NormalizeSubAnimPath strips this automatically when passed to wire_params/assign_controller/unwire_params.
• get_wired_params returns paths with [#name] format. These paths can be passed directly to unwire_params — NormalizeSubAnimPath handles both [name] and [#name] formats.
• add_controller_target only works on script, expression, and constraint controllers. Noise/Bezier/other controllers will return a clear error message. Use assign_controller with controller_type:"float_script" if you need node references.

8. MAXScript Pitfalls

• No parens with keyword args: Box width:10 not Box() width:10
• Case-insensitive but avoid ambiguous short names
• Wrap in try/catch: try (...) catch (ex) (ex) — errors otherwise appear as generic failures
• Escape strings: use src.helpers.maxscript.safe_string, use MCP_Server.escapeJsonString in MAXScript
• Noise vs Noisemodifier: texture map vs modifier
• (getDir #temp) is Max temp, not OS temp
• .NET strings: convert to MAXScript strings before using string methods
• assign_controller/wire_params track paths may fail with display-style tokens like [#Transform][#Position][#Z Position]; normalize to lowercase underscore form like [#transform][#position][#z_position].

UberBitmap + Shell Material Workflow

• create_shell_material builds a Shell Material wrapping Arnold (render) + glTF (export)
• Arnold render slot uses UberBitmap2.osl (OSLMap) for all texture loading — NOT ai_image or Bitmaptexture
• UberBitmap2.osl path: (getDir #maxroot) + "OSL\\UberBitmap2.osl" — do NOT search for it
• All built-in OSL shaders live in <maxroot>\OSL\
• Packed ORM textures are split via MultiOutputChannelTexmapToTexmap:
  • Output 1 = Col (RGB), 2 = R, 3 = G, 4 = B, 5 = A, 6 = Luminance, 7 = Average
• Standard ORM wiring: BaseColor×AO(R) via ai_multiply → base_color, G → specular_roughness, B → metalness
• Shell Material slots: originalMaterial (slot 0, render) = Arnold, bakedMaterial (slot 1, export) = glTF
• renderMtlIndex = 0 (Arnold for rendering), viewportMtlIndex = 1 (glTF for viewport/export)
• When ORM texture detected in _DEFAULT_CHANNEL_PATTERNS, prefer packed split over separate roughness/metallic files
• replace_material / batch_replace_materials for swapping materials across objects

OSL Shader Rules

• Use write_osl_shader — handles file I/O, compilation, global storage
• Use introspect_osl to inspect any OSL shader's properties and output channels before wiring
• Shader function name MUST match shader_name exactly
• Use unique shader names — reusing hits stale cache
• OSLMap lowercases all param names — use lowercase keys
• introspect_class is blocked for OSLMap (663K+ output) — always use introspect_osl instead
• After creation, wire via set_material_property

9. C++ SDK Pitfalls

• is_array() / is_string() / is_number_*() / is_boolean() macro collision with MAXScript headers — use .type() == json::value_t::array / ::string / ::number_float / ::number_integer / ::boolean instead
• Matrix3(1) deprecated in Max 2026 — use Matrix3() default
• Modifier::GetName(bool localized) — use mod->GetName(false).data()
• ClassDesc::ClassName() returns const MCHAR*, not a string class
• Arnold/scripted plugins don't register in DllDir under MAXScript names — fall back to RunMAXScript for creation
• WStr::operator bool deleted in Max 2026 — use .data() && .data()[0] checks
• Native scene-delta baselines must be scoped per pipe client and cleared on scene reset/fetch; one process-global snapshot leaks across simultaneous agents and unrelated scenes.

10. MAXScript Reference Files

This skill includes bundled MAXScript reference files for writing correct MAXScript. Read the relevant file BEFORE writing MAXScript code for unfamiliar areas.

IMPORTANT: Before writing any MAXScript, READ the relevant file. Do not guess syntax.

Location: skills/3dsmax-mcp-dev/ in the project root. Example:

Read: skills/3dsmax-mcp-dev/maxscript-materials-textures.md

11. Architecture

Agent <-> FastMCP (Python/stdio) <-> Named Pipe <-> C++ GUP Plugin <-> 3ds Max SDK
                                  |
                                  +-> TCP:8765 fallback -> MAXScript listener

• 76 native C++ handlers via named pipe (pure SDK, 86-130x faster)
• Multi-instance pipe — multiple agents connect simultaneously
• Safe mode on pipe — blocks DOSCommand, ShellLaunch, deleteFile, python.Execute, createFile
• ScriptSource::NonEmbedded — .NET calls work through the pipe
• client.native_available routes tools to native or MAXScript path
• Remaining tools use MAXScript through ExecuteMAXScriptScript() in the C++ bridge

Adding a native handler

1. Add handler function to relevant .cpp in native/src/handlers/
2. Declare in native_handlers.h
3. Route in command_dispatcher.cpp
4. Add source to CMakeLists.txt
5. Update Python tool with if client.native_available: + MAXScript fallback
6. Build → deploy → restart Max

Unwrap UVW Editor

• The macroscript OpenUnwrapUI does NOT open the UV editor window
• To open the editor: modifierInstance.edit() on the Unwrap_UVW modifier (e.g. $Box001.modifiers[#Unwrap_UVW].edit())
• Action table "Unwrap UVW" has 228 actions including "Edit UVW's" (id 40005)
• Use list_macroscripts and list_action_tables to discover available commands — don't guess names

System Discovery (native handlers)

• list_macroscripts — walks MacroDir, 4000+ macros, filter by category/pattern
• list_action_tables — walks IActionManager, 100+ tables with all menu/shortcut actions
• introspect_interface — full FPInterface dump (functions, properties, enums with live values)
• invoke_interface — call FPInterface functions + set properties directly, no MAXScript parsing
• run_macroscript — execute macroscripts by category + name via MacroEntry::Execute()
• Use these to discover any plugin's API surface before guessing MAXScript commands

Converted and distributed by TomeVault — claim your Tome and manage your conversions.