99 lines
5.1 KiB
Markdown
99 lines
5.1 KiB
Markdown
# USD Layer Manager
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A C++17 / Windows desktop application providing a **Maya Render Layers-style** USD scene editor using **OpenUSD v25.05**, **ImGui 1.92.7** (docking branch), and **OpenGL 3.3** (via GLAD). Users can open, edit, and save USD files, manage layered stage overrides, inspect and edit prim properties, and interact with 3D scenes through a Hydra viewport.
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## Features
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- **Layer Stack Management** — Create, reorder, mute/unmute sublayers with full undo support
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- **Scene Hierarchy** — Browse prim tree with per-type SVG icons; create, delete, rename prims; add/replace references
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- **Property Editor** — Maya Channel Box-style attribute editing with type-aware drag inputs, color pickers, and undoable transforms
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- **3D Viewport** — Hydra rendering via `UsdImagingGLEngine` into an offscreen FBO; switchable render delegates; grid overlay; selection bounding boxes; camera wireframes
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- **Camera Control** — Free orbital camera (tumble/truck/dolly) or drive from USD camera prims; auto near/far clipping; frame selection
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- **Transform Gizmo** — Pure ImDrawList-based manipulator (translate/rotate/scale) in object or world space
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- **Undo/Redo** — Full command history for prim creation/deletion, attribute edits, transform changes, and layer operations
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- **Multi-select** — Rectangular selection in viewport with cross-panel syncing
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## Dependencies
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| Dependency | Version | Notes |
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| [OpenUSD](https://github.com/PixarAnimationStudios/OpenUSD) | v25.05 | Prebuilt; found via `FindOpenUSD.cmake` |
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| [Dear ImGui](https://github.com/ocornut/imgui) | v1.92.7 | Docking branch; Win32 + OpenGL3 backends |
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| [GLAD](https://glad.dav1d.de/) | — | OpenGL 3.3 core loader |
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| Python | 3.12 | Required by OpenUSD runtime (`python312.dll`) |
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## Build
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### Prerequisites
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- Visual Studio 17 2022 (MSVC v143) with C++17 support
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- CMake 3.20+
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- Python 3.12 installed at `%LOCALAPPDATA%\Programs\Python\Python312\`
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### Steps
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```powershell
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cmake --preset default
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cmake --build build --config Release
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cmake --install build --config Release
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```
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The installed `App.exe` lives in `install/bin/`.
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**Presets** — `default` (Release + tests), `debug`, `release`, `no-tests`.
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### Tests
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```powershell
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cmake --build build --config Release
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ctest --test-dir build -C Release
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```
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## Architecture
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```
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src/
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├── main.cpp — Entry point (plugin path init, app lifecycle)
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├── core/ — USD business logic (no UI dependency)
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│ ├── UsdStageManager — Stage open/create/save/close lifecycle
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│ ├── LayerManager — Layer stack introspection and mutation
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│ ├── PropertyManager — Property read/write via edit target
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│ ├── CommandHistory — Undo/redo stack for ICommand instances
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│ ├── UsdSceneRenderer — Hydra rendering + picking + overlays
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│ ├── ViewportCamera — Free / USD-camera-driven orbital camera
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│ └── commands/ — ICommand subclasses for all mutable operations
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├── ui/ — ImGui panels and application shell
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│ ├── Application — App shell (owns managers/panels, docking, menus)
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│ ├── ImGuiContext — Win32+OpenGL+ImGui initialization and loop
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│ ├── ViewportPanel — 3D viewport with toolbar, picking, camera
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│ ├── SceneHierarchyPanel — Prim tree browser with context menus
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│ ├── PropertyPanel — Attribute/transform editor (channel box-style)
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│ ├── LayerPanel — Layer stack editor with modal dialogs
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│ ├── TransformManipulator — ImDrawList gizmo (move/rotate/scale)
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│ └── IconManager — SVG icon rasterization via NanoSVG
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└── utils/ — Cross-cutting utilities
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├── Logger — Thread-safe logging (file + console)
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├── FileDialog — Win32 file open/save dialogs
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├── PathUtils — Exe-relative path resolution
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└── GLExt — GLAD extension initialization
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```
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## Key Design Patterns
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- **Command Pattern** — All mutable USD operations go through `ICommand` → `CommandHistory` for undo/redo
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- **Panel-Manager Separation** — UI panels hold pointers to core managers but contain no USD layer/prim logic
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- **Callback Wiring** — Cross-panel communication via `std::function` callbacks (e.g. viewport pick → hierarchy select → property panel update)
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- **Render-Delegate Plugability** — `UsdSceneRenderer` can switch Hydra render plugins at runtime
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- **Gizmo as 2D Overlay** — `TransformManipulator` uses pure `ImDrawList` calls (no GL resources), same approach as ImGuizmo
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## Project Configuration
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| Config | Purpose |
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| `cmake/modules/FindOpenUSD.cmake` | OpenUSD SDK discovery |
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| `cmake/modules/FindImgui.cmake` | ImGui source integration |
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| `cmake/modules/FindGlad.cmake` | GLAD loader setup |
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| `CMakePresets.json` | Build presets (VS 17 2022, x64) |
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| `AGENTS.md` | AI agent build/architecture guide | |