200 lines
4.8 KiB
Markdown
200 lines
4.8 KiB
Markdown
# Mesh Operations
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## Summary
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MatterControl provides comprehensive mesh processing capabilities through the agg-sharp/PolygonMesh libraries, supporting import/export of various formats, mesh manipulation, boolean operations, repair, and optimization.
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## Technical Description
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### Mesh Architecture
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```
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Mesh (PolygonMesh)
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├── Vertices (Vector3 positions)
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├── Faces (triangles)
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├── FaceBsp (spatial acceleration)
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└── Properties
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├── BoundingBox
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└── Volume
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```
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### Supported Formats
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**Import:**
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| Format | Extension | Handler |
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|--------|-----------|---------|
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| STL | .stl | `StlProcessing` |
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| OBJ | .obj | `ObjSupport` |
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| AMF | .amf | `AmfDocument` |
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| 3MF | .3mf | `Object3D.Load()` |
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| MCX | .mcx | Native format |
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**Export:**
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| Format | Extension | Handler |
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|--------|-----------|---------|
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| STL (binary) | .stl | `MeshFileIo.Save()` |
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| STL (ASCII) | .stl | `MeshFileIo.Save()` |
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| AMF | .amf | `AmfDocument.Save()` |
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| 3MF | .3mf | `Object3D.Save()` |
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### Mesh Processing
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Located in `Submodules/agg-sharp/PolygonMesh/Processors/`:
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| Processor | Purpose |
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|-----------|---------|
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| `MeshHelper` | Common mesh operations |
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| `StlProcessing` | STL import/export |
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| `CsgOperations` | Boolean operations |
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### Boolean Operations
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CSG (Constructive Solid Geometry):
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```csharp
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// Union
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Mesh result = CsgOperations.Union(meshA, meshB);
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// Subtraction
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Mesh result = CsgOperations.Subtract(meshA, meshB);
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// Intersection
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Mesh result = CsgOperations.Intersect(meshA, meshB);
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```
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**Implementation:**
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- Uses BSP trees for spatial partitioning
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- Handles coplanar faces
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- Produces manifold output
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### Mesh Repair
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`RepairObject3D` fixes common mesh issues:
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| Fix | Description |
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|-----|-------------|
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| Hole filling | Close open boundaries |
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| Duplicate removal | Remove coincident vertices |
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| Normal repair | Fix inverted normals |
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| Non-manifold | Repair non-manifold edges |
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### Mesh Decimation
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`DecimateObject3D` reduces polygon count:
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```csharp
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public class DecimateObject3D : MeshWrapperObject3D
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{
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public double ReductionPercent { get; set; } = 50;
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}
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```
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Uses edge collapse algorithm preserving shape.
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### Mesh Transforms
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| Operation | Method |
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|-----------|--------|
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| Translate | `mesh.Translate(offset)` |
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| Rotate | `mesh.Transform(rotationMatrix)` |
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| Scale | `mesh.Transform(scaleMatrix)` |
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| Mirror | Transform with negative scale |
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### Spatial Acceleration
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`FaceBspTree` provides fast ray intersection:
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```csharp
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var bspTree = FaceBspTree.Create(mesh);
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var hit = bspTree.GetClosestIntersection(ray);
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```
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Uses for:
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- Object selection (picking)
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- Collision detection
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- Boolean operations
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### MCX Format
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Native scene format (JSON-based):
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```
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MCX file (ZIP archive)
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├── manifest.json (metadata)
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├── scene.json (scene graph)
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└── Assets/
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└── {guid}.stl (mesh files)
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```
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**Benefits:**
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- Preserves scene hierarchy
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- Stores parametric data
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- Includes thumbnails
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### Mesh Helpers
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Utility methods in `MeshHelper`:
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| Method | Purpose |
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|--------|---------|
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| `CreateCylinder()` | Generate cylinder mesh |
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| `CreateCube()` | Generate box mesh |
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| `CreateSphere()` | Generate sphere mesh |
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| `CopyFaces()` | Duplicate face subset |
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| `Split()` | Split mesh by plane |
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### Volume Calculation
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```csharp
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double volume = mesh.GetVolume();
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AxisAlignedBoundingBox bounds = mesh.GetAxisAlignedBoundingBox();
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```
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Used for:
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- Material estimation
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- Scale validation
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- Build volume checking
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### Design Rationale
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**Custom Mesh Library**: Using PolygonMesh provides:
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- Full control over algorithms
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- Optimized for 3D printing use cases
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- No external dependencies
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**BSP Acceleration**: Spatial indexing enables:
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- Fast ray casting for selection
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- Efficient boolean operations
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- Real-time collision checks
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**MCX Format**: Custom format allows:
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- Full scene preservation
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- Parametric object storage
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- Efficient streaming
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## Reference
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### Core Classes
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| Class | Location | Description |
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|-------|----------|-------------|
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| `Mesh` | Submodules/agg-sharp/PolygonMesh | Mesh data structure |
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| `Face` | Submodules/agg-sharp/PolygonMesh | Triangle face |
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| `Vertex` | Submodules/agg-sharp/PolygonMesh | Vertex data |
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### Processing
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| Class | Location | Description |
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|-------|----------|-------------|
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| `StlProcessing` | Submodules/agg-sharp | STL I/O |
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| `CsgOperations` | Submodules/agg-sharp | Boolean ops |
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| `MeshHelper` | Submodules/agg-sharp | Utilities |
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| `FaceBspTree` | Submodules/agg-sharp | Spatial index |
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### MatterControl Classes
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| Class | Location | Description |
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|-------|----------|-------------|
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| `RepairObject3D` | [DesignTools/Operations/](MatterControlLib/DesignTools/Operations/) | Mesh repair |
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| `DecimateObject3D` | [DesignTools/Operations/](MatterControlLib/DesignTools/Operations/) | Decimation |
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| `MeshContentProvider` | [Library/ContentProviders/](MatterControlLib/Library/ContentProviders/) | Mesh loading |
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