对象遮挡的SceneKit LiDAR特性

Question

使用LiDAR的对象遮挡在RealityKit中使用场景理解选项。基本上，扫描几何是用于遮挡。

arView.environment.sceneUnderstanding.options.insert(.occlusion)

遗憾的是，SceneKit中没有包括这一点。虽然仍然可以通过LiDAR通过ARMeshAnchor获取扫描的几何图形，但对象遮挡必须从这个几何图形中手工完成。下面是关于它的讨论：苹果论坛

这种方法是否已经有了解决办法？

Answer 1

我通过这样的操作在SceneKit中实现了对象遮挡：

//Before starting session, put this option in configuration
if ARWorldTrackingConfiguration.supportsSceneReconstruction(.mesh) {
        configuration.sceneReconstruction = .mesh
} else {
        // Handle device that doesn't support scene reconstruction
}
// Run the view's session
sceneView.session.run(configuration)

在这种方法中，您将获得场景重建网格，因此可以这样实现它

func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
    guard let meshAnchor = anchor as? ARMeshAnchor else {
            return nil
        }

    let geometry = createGeometryFromAnchor(meshAnchor: meshAnchor)

    //apply occlusion material
    geometry.firstMaterial?.colorBufferWriteMask = []
    geometry.firstMaterial?.writesToDepthBuffer = true
    geometry.firstMaterial?.readsFromDepthBuffer = true
        

    let node = SCNNode(geometry: geometry)
    //change rendering order so it renders before  our virtual object
    node.renderingOrder = -1
    
    return node
}

当网格更新时更新节点

func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
    guard let meshAnchor = anchor as? ARMeshAnchor else {
            return
        }
    let geometry = createGeometryFromAnchor(meshAnchor: meshAnchor)

        // Optionally hide the node from rendering as well
        geometry.firstMaterial?.colorBufferWriteMask = []
        geometry.firstMaterial?.writesToDepthBuffer = true
        geometry.firstMaterial?.readsFromDepthBuffer = true
        

    node.geometry = geometry
}

其余方法

// Taken from https://developer.apple.com/forums/thread/130599
func createGeometryFromAnchor(meshAnchor: ARMeshAnchor) -> SCNGeometry {
    let meshGeometry = meshAnchor.geometry
    let vertices = meshGeometry.vertices
    let normals = meshGeometry.normals
    let faces = meshGeometry.faces
    
    // use the MTL buffer that ARKit gives us
    let vertexSource = SCNGeometrySource(buffer: vertices.buffer, vertexFormat: vertices.format, semantic: .vertex, vertexCount: vertices.count, dataOffset: vertices.offset, dataStride: vertices.stride)
    
    let normalsSource = SCNGeometrySource(buffer: normals.buffer, vertexFormat: normals.format, semantic: .normal, vertexCount: normals.count, dataOffset: normals.offset, dataStride: normals.stride)
    // Copy bytes as we may use them later
    let faceData = Data(bytes: faces.buffer.contents(), count: faces.buffer.length)
    
    // create the geometry element
    let geometryElement = SCNGeometryElement(data: faceData, primitiveType: primitiveType(type: faces.primitiveType), primitiveCount: faces.count, bytesPerIndex: faces.bytesPerIndex)
    
    return SCNGeometry(sources: [vertexSource, normalsSource], elements: [geometryElement])
}

func primitiveType(type: ARGeometryPrimitiveType) -> SCNGeometryPrimitiveType {
        switch type {
            case .line: return .line
            case .triangle: return .triangles
        default : return .triangles
        }
}