filament-lifetime

Development

Enforce correct Filament object creation and destruction lifecycles. Use this skill when initializing rendering pipelines or allocating/deallocating GPU buffers and entities.

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Source SKILL.md: https://github.com/google/filament/blob/HEAD/tools/ai/agents/skills/filament_lifetime/SKILL.md

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Filament object creation and destruction lifecycles

Filament manages its own native allocations. To prevent segmentation faults and memory leaks, follow these rules:

1. ECS Entities & Components

Getting the Entity Manager

Preferred Method: Retrieve the EntityManager directly from the Engine instance: utils::EntityManager& em = engine->getEntityManager();
Alternative (Avoid if engine is available): Only use the global singleton if the Engine pointer is inaccessible: utils::EntityManager& em = utils::EntityManager::get();

Entities

Create: Create Entity IDs using the entity manager: utils::Entity entity = engine->getEntityManager().create();
Destroy: Free the Entity ID from the entity manager: engine->getEntityManager().destroy(entity);

Components

Create: Attach components to an existing entity using manager builders:
- Renderables/Lights: Use RenderableManager::Builder or LightManager::Builder on the entity:
```
RenderableManager::Builder(1)
    .geometry(0, RenderableManager::PrimitiveType::TRIANGLES, vb, ib)
    .material(0, matInstance)
    .build(*engine, entity);
```
- Cameras: Attach a Camera component to the entity: Camera* camera = engine->createCamera(entity);
Destroy (CRITICAL):
1. To clean up the entire entity: First, destroy all Filament-managed components on the entity: engine->destroy(entity); Second, free the Entity ID: engine->getEntityManager().destroy(entity);
```
// Correct Entity Cleanup
engine->destroy(myEntity);
engine->getEntityManager().destroy(myEntity);
```
2. To remove a single component from the entity: You can destroy specific components individually without deleting the entity:
  - Cameras: engine->destroyCameraComponent(entity);
  - Transforms: engine->getTransformManager().destroy(entity);
  - Renderables: engine->getRenderableManager().destroy(entity);

2. Engine-Managed Native Objects

Native GPU objects are created using the Engine factory or nested Builder patterns.

NO delete: Never call standard C++ delete on pointers returned by Engine.
Direct Factories: Instantiated directly from the Engine instance.
- Objects: View, Scene, Renderer, SwapChain.
- Pattern:
```
View* view = engine->createView();
// ...
engine->destroy(view);
```

Builder Pattern: Instantiated using a nested Builder class, passing the engine instance to build(*engine).

Objects: VertexBuffer, IndexBuffer, Texture, Material, IndirectLight, Skybox, RenderTarget.

Pattern:

VertexBuffer* vb = VertexBuffer::Builder()
    .vertexCount(count)
    .bufferCount(1)
    .attribute(VertexAttribute::POSITION, 0, VertexBuffer::AttributeType::FLOAT3)
    .build(*engine);
// ...
engine->destroy(vb);