I think figured out what I was doing wrong. I was using the extents of the anchor to create meshes, then placing the meshes at the transform for the anchor. I was expecting an anchor plane to be something I could turn into a geometric plane.
Diving deeper into it, anchors are not planes the sense that a plane mesh is. These anchors are actually n-gons that don't necessarily line up with shape of a plane. Apple has an example project that creates these, but applies an occlusion material. I swapped that for a material with random colors so I could visualize what is happening. Each anchor has a n-gon, represented with meshVertices. The example project used some extensions to use that data to create shapes for the meshes.
Personally, I found the example project difficult to understand. It has way too much abstraction and stashes the good stuff in extensions.
Here is a modified version of the example from the first post, without the abstractions from the Apple example project.
I'd love to hear any more ideas from you folks. How can we improve this?
import SwiftUI
import RealityKit
import RealityKitContent
import ARKit
struct Example068: View {
@State var session = ARKitSession()
@State private var planeAnchors: [UUID: Entity] = [:]
@State private var planeColors: [UUID: Color] = [:]
var body: some View {
RealityView { content in
} update: { content in
for (_, entity) in planeAnchors {
if !content.entities.contains(entity) {
content.add(entity)
}
}
}
.task {
try! await setupAndRunPlaneDetection()
}
}
func setupAndRunPlaneDetection() async throws {
let planeData = PlaneDetectionProvider(alignments: [.horizontal, .vertical, .slanted])
if PlaneDetectionProvider.isSupported {
do {
try await session.run([planeData])
for await update in planeData.anchorUpdates {
switch update.event {
case .added, .updated:
let anchor = update.anchor
if planeColors[anchor.id] == nil {
planeColors[anchor.id] = generatePastelColor()
}
let planeEntity = createPlaneEntity(for: anchor, color: planeColors[anchor.id]!)
planeAnchors[anchor.id] = planeEntity
case .removed:
let anchor = update.anchor
planeAnchors.removeValue(forKey: anchor.id)
planeColors.removeValue(forKey: anchor.id)
}
}
} catch {
print("ARKit session error \(error)")
}
}
}
private func generatePastelColor() -> Color {
let hue = Double.random(in: 0...1)
let saturation = Double.random(in: 0.2...0.4)
let brightness = Double.random(in: 0.8...1.0)
return Color(hue: hue, saturation: saturation, brightness: brightness)
}
private func createPlaneEntity(for anchor: PlaneAnchor, color: Color) -> Entity {
let entity = Entity()
entity.name = "Plane \(anchor.id)"
entity.setTransformMatrix(anchor.originFromAnchorTransform, relativeTo: nil)
// Generate a mesh for the plane (for occlusion).
var meshResource: MeshResource? = nil
do {
var contents = MeshResource.Contents()
contents.instances = [MeshResource.Instance(id: "main", model: "model")]
var part = MeshResource.Part(id: "part", materialIndex: 0)
// Convert vertices to SIMD3<Float>
let vertices = anchor.geometry.meshVertices
var vertexArray: [SIMD3<Float>] = []
for i in 0..<vertices.count {
let vertex = vertices.buffer.contents().advanced(by: vertices.offset + vertices.stride * i).assumingMemoryBound(to: (Float, Float, Float).self).pointee
vertexArray.append(SIMD3<Float>(vertex.0, vertex.1, vertex.2))
}
part.positions = MeshBuffers.Positions(vertexArray)
// Convert faces to UInt32
let faces = anchor.geometry.meshFaces
var faceArray: [UInt32] = []
let totalFaces = faces.count * faces.primitive.indexCount
for i in 0..<totalFaces {
let face = faces.buffer.contents().advanced(by: i * MemoryLayout<Int32>.size).assumingMemoryBound(to: Int32.self).pointee
faceArray.append(UInt32(face))
}
part.triangleIndices = MeshBuffer(faceArray)
contents.models = [MeshResource.Model(id: "model", parts: [part])]
meshResource = try MeshResource.generate(from: contents)
} catch {
print("Failed to create a mesh resource for a plane anchor: \(error).")
}
var material = PhysicallyBasedMaterial()
material.baseColor.tint = UIColor(color)
if let meshResource {
entity.components.set(ModelComponent(mesh: meshResource, materials: [material]))
}
return entity
}
}
#Preview {
Example068()
}
