how do you use lowlevelmesh

To use low-level mesh in RealityKit, you can follow these steps:

1. Declare Vertex and Index Buffers: Start by declaring the required capacity for the vertex and index buffers. This involves specifying the list of vertex attributes and their layouts. Each vertex attribute uses one of the layouts, and you can use up to four Metal buffers for your vertex data.

2. Initialize Low-Level Mesh: Create a low-level mesh descriptor, which is conceptually similar to Metal's MTLVertexDescriptor but also contains information that RealityKit needs to ingest your mesh. Populate a list of parts, where each part spans a region of the index buffer. You can assign different RealityKit material indices to each mesh part.

3. Update Vertex Data: When it's time to update the vertex data of a low-level mesh, you can use the withUnsafeMutableBytes API. This API gives you access to the actual buffer that will be submitted to the GPU for rendering, minimizing overhead. You can also update your low-level mesh index buffers via withUnsafeMutableIndices.

4. Create Mesh Resource: Finally, create a mesh resource from your low-level mesh and assign it to an entity's model component.

For more detailed information, you can refer to the session Build a spatial drawing app with RealityKit.

Relevant Sessions

• Build a spatial drawing app with RealityKit
• Bring your iOS or iPadOS game to visionOS

If you need more specific details or examples, please let me know!