# Skill: VTK Visualization Pipeline

This skill defines how to bridge domain objects with the VTK 3D visualization layer.

## Context
- **Wrapper**: `Prop3D` (wraps a `vtkProp`).
- **Mapping**: `Viewport` maintains `m_ObjectToProp3D` for synchronization.
- **GUI Integration**: `QViewport` handles Qt events and selection signals.

## Implementation Patterns

### 1. Creating a Prop3D
A `Prop3D` should wrap a domain object and update its visual state when the object changes.
```cpp
class MyProp3D : public Prop3D {
public:
    MyProp3D(MyObject* obj) : Prop3D(obj) {
        // Connect domain updates to visual refreshes
        uLib::Object::connect(obj, &Object::Updated, [this]() { this->SyncFromObject(); });
        
        // Expose properties to the VTK side-panel
        ULIB_ACTIVATE_DISPLAY_PROPERTIES(*this)
    }
    
    void SyncFromObject() {
        // Update VTK actors/mappers from MyObject's properties
    }
};
```

### 2. Display Properties
Use `serialize_display` to choose which properties of the domain object or the `Prop3D` itself are visible in the sliding "Display Properties" panel in `gcompose`.
```cpp
void serialize_display(Archive::display_properties_archive &ar) {
    ar & boost::serialization::make_hrp("Opacity", m_Opacity);
    ar & boost::serialization::make_hrp("Wireframe", m_Wireframe);
}
```

### 3. Transformation Sync (TRS)
Always synchronize the object's `trs` (Translate, Rotate, Scale) with the VTK actor's user transform.
```cpp
void UpdateTransform() {
    auto matrix = GetContent()->GetTransform().GetMatrix();
    m_Actor->SetUserMatrix(uLib::ToVtkMatrix(matrix));
}
```

## Checklist
- [ ] Does the `Prop3D` connect to the object's `Updated()` signal?
- [ ] Are `ULIB_ACTIVATE_DISPLAY_PROPERTIES` and `serialize_display` implemented?
- [ ] Is the transformation (TRS) correctly mapped to the VTK actor?