feat: add UMaterialFunction support to material authoring handlers by nekwo · Pull Request #352 · ChiR24/Unreal_mcp

nekwo · 2026-04-14T06:50:40Z

Summary

Material authoring handlers (get_material_info, add_material_node, get_material_node_details, use_material_function) only worked with UMaterial assets. Passing a UMaterialFunction path would fail with ASSET_NOT_FOUND. There was also no way to introspect a material function's inputs and outputs. Additionally, SanitizeProjectRelativePath used a manual /Content/ heuristic for plugin paths that rejected valid game feature plugin mount points.

Changes

get_material_info, add_material_node, get_material_node_details now accept both UMaterial and UMaterialFunction paths via a new LoadMaterialOrFunction helper
use_material_function supports MF-in-MF calls (placing a function call node inside another material function), with self-reference guard
New get_material_function_info sub-action returning function inputs (name, EFunctionInputType, preview/default values, sort priority, description) and outputs
Added MCP_GET_FUNCTION_EXPRESSIONS version-compat macro for UE 5.0–5.7+
SanitizeProjectRelativePath now uses FPackageName::IsValidLongPackageName instead of manual heuristic, correctly recognizing all registered engine mount points (game feature plugins like /EterniaCore/, /ShooterCore/, /ALS/, etc.)
TypeScript handler and tool schema updated with get_material_function_info action
CHANGELOG.md updated

Related Issues

None

Type of Change

🐛 Bug fix (non-breaking change that fixes an issue)
✨ New feature (non-breaking change that adds functionality)
💥 Breaking change (fix or feature that would cause existing functionality to change)
📚 Documentation update
🔧 Configuration/build change
♻️ Refactoring (no functional changes)
🧪 Test addition/update

Testing

Tested with Unreal Engine (version: 5.x)
Tested MCP client integration (client: Claude Desktop)
Added/updated tests

Pre-Merge Checklist

Code follows project style guidelines
Self-reviewed the code
Updated relevant documentation (if needed)
Added/updated tests (if applicable)
CI passes

get_material_info, add_material_node, get_material_node_details, and use_material_function now accept UMaterialFunction paths in addition to UMaterial. Added get_material_function_info sub-action that returns function inputs (name, EFunctionInputType, preview values, sort priority) and outputs. use_material_function supports MF-in-MF calls with self-reference guard. Includes MCP_GET_FUNCTION_EXPRESSIONS version-compat macro for UE 5.0-5.7+ and improved path validation using FPackageName::IsValidLongPackageName. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

coderabbitai · 2026-04-14T06:50:47Z

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github-actions · 2026-04-14T06:50:49Z

👋 Thanks for your first Pull Request! We love contributions. Please ensure you have signed off your commits and followed the contribution guidelines.

devin-ai-integration

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 5 additional findings.

…ies, batch operations New actions: - get_node_properties: full property dump per node type (CE code/inputs, params, MFC pins, generic UPROPERTY fallback) - set_static_switch_parameter_value: set static switch on material instances - delete_node: batch removal with auto-disconnect (single or array) - update_custom_expression: modify code/inputs/outputs of existing CE - get_node_chain: BFS path trace between two nodes or to a material pin - get_connected_subgraph: island detection with orphansOnly flag Enhanced actions: - get_node_connections: direction/depth/upstream/downstream graph traversal with hop distances, fixes missing output connections - get_material_info: filter=expressions includes CE code, filter=connections supports nodeId/nodeIds filtering - find_node: deduplicated results with connectionCount - compile_material: UMaterialFunction fallback - connect_nodes: MaterialFunctionCall input/output pin iteration - set_blend_mode/set_shading_model/set_material_domain: graceful MF rejection Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

github-actions · 2026-04-14T13:35:12Z

📏 Large PR Detected

This pull request is quite large (1000+ lines changed), which can make reviewing challenging.

Suggestions:

Consider breaking this into smaller, focused PRs
Separate refactoring from new features
Split bug fixes from feature additions

This helps reviewers provide better feedback and speeds up the merge process. Thank you! 🙏

…ndling GUID-based node IDs caused silent collisions on copy-pasted expressions. Switch to GetName() (e.g. "MaterialExpressionCustom_0") as canonical ID, add MCP_NODE_ID() macro, template-based FindExpressionInArray with 5-tier resolution (expr_N index, object name, GUID backwards-compat with collision warning, full path, semantic name match). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

auto* range-for fails to deduce type from TObjectPtr elements in UE 5.1+. Switch to indexed for-loops with explicit static_cast<UMaterialExpression*>. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nekwo · 2026-04-14T14:23:02Z

sorry for the big pr but material function support is kind of ridiculous in the amount of edge cases for it to be smooth due to things like recursion and node id checks

but claude scripts materials like a beast now

The path normalization pattern `if (!StartsWith("/Game/")) prepend "/Game/"` clobbered valid plugin mount paths like /EterniaCore/. Since SanitizeProjectRelativePath already validates against registered engine mount points via FPackageName::IsValidLongPackageName, only prepend /Game/ for bare relative paths that lack a leading /. Also accept 'path' as an alias for 'folder' in all widget creation handlers (create_widget_blueprint, create_settings_menu, etc.). Fixed in: WidgetAuthoringHandlers, AudioHandlers, LevelStructureHandlers, McpAutomationBridgeHelpers.h (ValidateAndBuildAssetPath). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

set_property previously required objectPath which couldn't resolve Blueprint Class Default Objects (CDO path format Default__ClassName_C is not findable via standard object resolution). Now accepts blueprintPath as an alternative — loads the Blueprint, gets GeneratedClass->GetDefaultObject(), and mutates properties on the CDO directly. This enables scripted style/theme authoring for CommonUI button styles and other Blueprint-based data assets. Also fixes ResolveObjectFromPath to support plugin content mount points (e.g. /EterniaCore/) — previously only /Game/, /Engine/, /Script/ were recognized. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…ImportText Uses FProperty::ImportText_Direct for fully reflection-based property setting on any widget class. Supports two modes: - Legacy: pass style param to set the Style property (backwards compat) - Generic: pass propertyName + value to set any property via UE reflection Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Read mode: omit value to export current property value via ExportText - Write mode: Modify() + ImportText + PostEditChangeProperty instead of full blueprint recompile (MarkBlueprintAsStructurallyModified only for structural changes like clipping) - Returns exportedValue for write verification - Validates propertyName instead of value (value empty = read mode) Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…operty Add IsValid() check before accessing Payload fields to prevent null dereference on malformed requests, matching HandleGetObjectProperty. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- set_style: use bHasValueField (field presence) instead of Value.IsEmpty() to distinguish read mode (omitted field) from write with empty string - set_style: coerce JSON number/bool values to string for ImportText - set_style: add UE 5.0 compat (#if for ImportText vs ImportText_Direct) - set_style: use MCP_PROPERTY_EXPORT_TEXT macro for ExportText compat - set_style: restore MarkBlueprintAsStructurallyModified for set_clipping, remove unreachable dead else branch - inspect:set_property: normalize blueprintPath (trim + strip trailing /) and add tool context to validation error message - pipeline-handlers: add 5s timeout to execAsync PATH lookup Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…nections error, path sanitization - Rename nodeGuid to nodeId in add_material_node response - Add AddVerification to connect_material_pins response - Guard FinalizeHost behind bCleared and report INVALID_PIN for unknown pins - Add SanitizeProjectRelativePath to all 7 remaining widget template actions Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nekwo · 2026-04-15T22:13:38Z

Did all the devin fixes, pushed my other pr to dev by accident, but realized you have coderabbit disabled here.. so i presume you expect it all pushed to dev, let me do that

i was working on main to confirm stability

github-actions Bot added size/l area/server area/docs area/plugin labels Apr 14, 2026

nekwo mentioned this pull request Apr 14, 2026

UE 5.7.3 - Crash inspecting material function + potential fix #225

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github-actions Bot added size/xl and removed size/l labels Apr 14, 2026

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nekwo and others added 2 commits April 14, 2026 09:54

fix: use indexed loops in FindExpressionInArray for TObjectPtr compat

f37e0f8

auto* range-for fails to deduce type from TObjectPtr elements in UE 5.1+. Switch to indexed for-loops with explicit static_cast<UMaterialExpression*>. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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nekwo and others added 10 commits April 14, 2026 13:05

Merge branch 'fix/set-cdo-property' into team

61aa078

Merge branch 'fix/set-cdo-property' into team

b067313

Merge branch 'fix/set-cdo-property' into team

e372850

fix: guard Payload validity before dereferencing in HandleSetObjectPr…

6c2cb8c

…operty Add IsValid() check before accessing Payload fields to prevent null dereference on malformed requests, matching HandleGetObjectProperty. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Merge branch 'fix/set-cdo-property' into team

7fc2c18

Merge branch 'fix/set-cdo-property' into team

e12959c

coderabbitai Bot approved these changes Apr 15, 2026

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nekwo closed this Apr 15, 2026

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feat: add UMaterialFunction support to material authoring handlers#352

feat: add UMaterialFunction support to material authoring handlers#352
nekwo wants to merge 16 commits into
ChiR24:mainfrom
nekwo:feat/material-function-support

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Summary

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Pre-Merge Checklist

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