Object occlusion with LiDAR works in RealityKit with the scene understanding option. Basically the scanned geometry is used for the occlusion.
arView.environment.sceneUnderstanding.options.insert(.occlusion)
Sadly this is not included in SceneKit. While it is still possible to get the scanned geometry from LiDAR via ARMeshAnchor, the object occlusion has to de done by hand from this geometry. Here is discussion on it: Apple Forum
Is there already a solution for this approach?
I acheived object occlusion in SceneKit by doing something like this:
//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)
You will get scene reconstruction mesh in this method, so implement it like this
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
}
Update your node when mesh updates
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
}
Rest of methods
// 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
}
}
