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Update README for multi-model support and frustum culling

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Reflect current architecture: per-model streamers, glMultiDrawElements
with frustum culling, 32-byte vertex format with color, multiselect
file picker, settings/stats files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Dion Moult
2026-04-11 20:55:24 +10:00
parent 83a3131276
commit 5b4c1089cf
1 changed files with 19 additions and 14 deletions
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src/ifcviewer/README.md
+19 -14
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@@ -10,21 +10,22 @@ A high-performance native IFC viewer built on IfcOpenShell's C++ geometry engine
| +----------+ +--------------------------+|
| | Element | | 3D Viewport ||
| | Tree | | (QWindow + OpenGL 4.5) ||
| | | | ||
| +----------+ | Single VBO/EBO ||
| | Property | | DrawElementsBaseVertex ||
| | (per- | | ||
| | model) | | Single VBO/EBO ||
| +----------+ | glMultiDrawElements ||
| | Property | | frustum culling ||
| | Table | | GPU pick pass ||
| +----------+ +--------------------------+|
| | Status / Progress |
| | Status / Progress / Stats |
+-------------------------------------------+
^ ^
| |
element metadata UploadChunks
| |
+-------------------------------------------+
| GeometryStreamer (background QThread) |
| GeometryStreamer (one per loaded model) |
| IfcGeom::Iterator with N threads |
| (one per CPU core by default) |
| (models loaded sequentially) |
+-------------------------------------------+
```
@@ -32,8 +33,10 @@ A high-performance native IFC viewer built on IfcOpenShell's C++ geometry engine
- **QWindow viewport** embedded via `QWidget::createWindowContainer()`. This gives us a raw native surface for OpenGL, bypassing `QOpenGLWidget`'s compositor overhead.
- **One big vertex buffer + index buffer** (64 MB + 32 MB initial). Geometry is appended as it streams in. No per-object VBOs, no rebinding.
- **Interleaved vertex format**: position (3 floats) + normal (3 floats) + object ID (1 float, bitcast uint32) = 28 bytes per vertex.
- **Interleaved vertex format**: position (3 floats) + normal (3 floats) + object ID (1 float, bitcast uint32) + color (RGBA8 packed into 1 float) = 32 bytes per vertex.
- **Per-object frustum culling**: each object's AABB is tested against 6 frustum planes each frame. Only visible objects are drawn via `glMultiDrawElements`.
- **GPU object picking**: a second render pass writes object IDs to an R32UI framebuffer. Click reads back one pixel. No CPU-side raycasting.
- **Multi-model support**: multiple IFC files can be loaded simultaneously. Each model gets its own `GeometryStreamer` (owning the `ifcopenshell::file` for property lookup). Models are loaded sequentially; geometry from all models coexists in the shared VBO/EBO. Per-model visibility toggle and removal are supported.
- **Multi-threaded tessellation**: `IfcGeom::Iterator` runs on a background thread and internally parallelizes geometry conversion across all CPU cores.
- **Non-blocking streaming**: the iterator emits `UploadChunk` signals via Qt's queued connection. The main thread uploads to the GPU without blocking iteration.
- **World coordinates**: geometry is emitted in world space (`use-world-coords=true`) so no per-object transform matrices are needed on the GPU.
@@ -43,9 +46,11 @@ A high-performance native IFC viewer built on IfcOpenShell's C++ geometry engine
| File | Purpose |
|------|---------|
| `main.cpp` | Application entry point, GL 4.5 surface format, CLI argument parsing |
| `MainWindow.h/cpp` | Qt main window: dockable element tree, property table, status bar, menus |
| `ViewportWindow.h/cpp` | OpenGL 4.5 Core renderer: shaders, buffer management, camera, picking |
| `GeometryStreamer.h/cpp` | Background geometry processing: loads IFC, runs iterator, emits chunks |
| `MainWindow.h/cpp` | Qt main window: multi-model project management, element tree, property table, status bar |
| `ViewportWindow.h/cpp` | OpenGL 4.5 Core renderer: shaders, buffer management, camera, frustum culling, picking |
| `GeometryStreamer.h/cpp` | Background geometry processing: loads IFC, runs iterator, emits chunks (one per model) |
| `AppSettings.h/cpp` | Persisted application preferences (geometry library, show stats) |
| `SettingsWindow.h/cpp` | Settings dialog UI |
| `CMakeLists.txt` | Build configuration |
## Dependencies
@@ -94,10 +99,10 @@ make -j$(nproc)
## Usage
```sh
# Open a file directly
./IfcViewer model.ifc
# Open one or more files from the command line
./IfcViewer arch.ifc struct.ifc mep.ifc
# Or use File -> Open from the menu
# Or use File -> Add Files from the menu (supports multiselect)
./IfcViewer
```
@@ -114,7 +119,7 @@ make -j$(nproc)
| Key | Action |
|-----|--------|
| Ctrl+O | Open file |
| Ctrl+O | Add files |
| Ctrl+Q | Quit |
## Performance Strategy