如何将最新iPad Pro上由新的SceneReconstruction API生成的ARMeshGeometry导出为.obj文件？
这是SceneReconstruction文档链接：https://developer.apple.com/documentation/arkit/world_tracking/visualizing_and_interacting_with_a_reconstructed_scene
4个回答
18
从苹果的Visualising Scene Scemantics示例应用程序开始，您可以从帧中的第一个锚点检索ARMeshGeometry对象。
导出数据的最简单方法是先将其转换为MDLMesh：
extension ARMeshGeometry {
func toMDLMesh(device: MTLDevice) -> MDLMesh {
let allocator = MTKMeshBufferAllocator(device: device);
let data = Data.init(bytes: vertices.buffer.contents(), count: vertices.stride * vertices.count);
let vertexBuffer = allocator.newBuffer(with: data, type: .vertex);
let indexData = Data.init(bytes: faces.buffer.contents(), count: faces.bytesPerIndex * faces.count * faces.indexCountPerPrimitive);
let indexBuffer = allocator.newBuffer(with: indexData, type: .index);
let submesh = MDLSubmesh(indexBuffer: indexBuffer,
indexCount: faces.count * faces.indexCountPerPrimitive,
indexType: .uInt32,
geometryType: .triangles,
material: nil);
let vertexDescriptor = MDLVertexDescriptor();
vertexDescriptor.attributes[0] = MDLVertexAttribute(name: MDLVertexAttributePosition,
format: .float3,
offset: 0,
bufferIndex: 0);
vertexDescriptor.layouts[0] = MDLVertexBufferLayout(stride: vertices.stride);
return MDLMesh(vertexBuffer: vertexBuffer,
vertexCount: vertices.count,
descriptor: vertexDescriptor,
submeshes: [submesh]);
}
}
一旦你有了MDLMesh，导出到OBJ文件就非常容易：
@IBAction func exportMesh(_ button: UIButton) {
let meshAnchors = arView.session.currentFrame?.anchors.compactMap({ $0 as? ARMeshAnchor });
DispatchQueue.global().async {
let directory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0];
let filename = directory.appendingPathComponent("MyFirstMesh.obj");
guard let device = MTLCreateSystemDefaultDevice() else {
print("metal device could not be created");
return;
};
let asset = MDLAsset();
for anchor in meshAnchors! {
let mdlMesh = anchor.geometry.toMDLMesh(device: device);
asset.add(mdlMesh);
}
do {
try asset.export(to: filename);
} catch {
print("failed to write to file");
}
}
}
- swiftcoder
7
8
@swiftcoder的答案非常好。但是在存在多个锚点的情况下，您需要根据锚点变换将顶点坐标转换为世界坐标系。否则，所有网格将被放置在零位置，会很混乱。
更新后的代码如下：
extension ARMeshGeometry {
func toMDLMesh(device: MTLDevice, transform: simd_float4x4) -> MDLMesh {
let allocator = MTKMeshBufferAllocator(device: device)
let data = Data.init(bytes: transformedVertexBuffer(transform), count: vertices.stride * vertices.count)
let vertexBuffer = allocator.newBuffer(with: data, type: .vertex)
let indexData = Data.init(bytes: faces.buffer.contents(), count: faces.bytesPerIndex * faces.count * faces.indexCountPerPrimitive)
let indexBuffer = allocator.newBuffer(with: indexData, type: .index)
let submesh = MDLSubmesh(indexBuffer: indexBuffer,
indexCount: faces.count * faces.indexCountPerPrimitive,
indexType: .uInt32,
geometryType: .triangles,
material: nil)
let vertexDescriptor = MDLVertexDescriptor()
vertexDescriptor.attributes[0] = MDLVertexAttribute(name: MDLVertexAttributePosition,
format: .float3,
offset: 0,
bufferIndex: 0)
vertexDescriptor.layouts[0] = MDLVertexBufferLayout(stride: vertices.stride)
return MDLMesh(vertexBuffer: vertexBuffer,
vertexCount: vertices.count,
descriptor: vertexDescriptor,
submeshes: [submesh])
}
func transformedVertexBuffer(_ transform: simd_float4x4) -> [Float] {
var result = [Float]()
for index in 0..<vertices.count {
let vertexPointer = vertices.buffer.contents().advanced(by: vertices.offset + vertices.stride * index)
let vertex = vertexPointer.assumingMemoryBound(to: (Float, Float, Float).self).pointee
var vertextTransform = matrix_identity_float4x4
vertextTransform.columns.3 = SIMD4<Float>(vertex.0, vertex.1, vertex.2, 1)
let position = (transform * vertextTransform).position
result.append(position.x)
result.append(position.y)
result.append(position.z)
}
return result
}
}
extension simd_float4x4 {
var position: SIMD3<Float> {
return SIMD3<Float>(columns.3.x, columns.3.y, columns.3.z)
}
}
extension Array where Element == ARMeshAnchor {
func save(to fileURL: URL, device: MTLDevice) throws {
let asset = MDLAsset()
self.forEach {
let mesh = $0.geometry.toMDLMesh(device: device, transform: $0.transform)
asset.add(mesh)
}
try asset.export(to: fileURL)
}
}
我不是 ModelIO 的专家，也许有更简单的方式来转换顶点缓冲区 :) 但这段代码对我有效。
- Alexander Gaidukov
5
看起来很不错！你能给我们提供一个完整的 ViewController.swift 的示例或者将你的项目上传到 Github 上吗？ - Florian Thürkow
2当然，Florian，在这里。https://github.com/alexander-gaidukov/LiDarDetector - Alexander Gaidukov
这很棒，有没有办法也保存模型的纹理？ - Chris
很遗憾，目前不支持顶点颜色或纹理。 - Alexander Gaidukov
2我已经成功添加了纹理坐标并导出了网格。在此处添加了该方法：https://dev59.com/qFIH5IYBdhLWcg3wC4KJ#61790146 - Pavan K
7
导出LiDAR重建的几何形状
这段代码可以将LiDAR的几何形状保存为USD格式并通过AirDrop发送到Mac电脑。您不仅可以导出.usd格式，还可以导出.usda、.usdc、.obj、.stl、.abc和.ply文件格式。
此外，您还可以使用SceneKit的write(to:options:delegate:progressHandler:)方法来保存.usdz版本的文件。
import RealityKit
import ARKit
import MetalKit
import ModelIO
@IBOutlet var arView: ARView!
var saveButton: UIButton!
let rect = CGRect(x: 50, y: 50, width: 100, height: 50)
override func viewDidLoad() {
super.viewDidLoad()
let tui = UIControl.Event.touchUpInside
saveButton = UIButton(frame: rect)
saveButton.setTitle("Save", for: [])
saveButton.addTarget(self, action: #selector(saveButtonTapped), for: tui)
self.view.addSubview(saveButton)
}
@objc func saveButtonTapped(sender: UIButton) {
print("Saving is executing...")
guard let frame = arView.session.currentFrame
else { fatalError("Can't get ARFrame") }
guard let device = MTLCreateSystemDefaultDevice()
else { fatalError("Can't create MTLDevice") }
let allocator = MTKMeshBufferAllocator(device: device)
let asset = MDLAsset(bufferAllocator: allocator)
let meshAnchors = frame.anchors.compactMap { $0 as? ARMeshAnchor }
for ma in meshAnchors {
let geometry = ma.geometry
let vertices = geometry.vertices
let faces = geometry.faces
let vertexPointer = vertices.buffer.contents()
let facePointer = faces.buffer.contents()
for vtxIndex in 0 ..< vertices.count {
let vertex = geometry.vertex(at: UInt32(vtxIndex))
var vertexLocalTransform = matrix_identity_float4x4
vertexLocalTransform.columns.3 = SIMD4<Float>(x: vertex.0,
y: vertex.1,
z: vertex.2,
w: 1.0)
let vertexWorldTransform = (ma.transform * vertexLocalTransform).position
let vertexOffset = vertices.offset + vertices.stride * vtxIndex
let componentStride = vertices.stride / 3
vertexPointer.storeBytes(of: vertexWorldTransform.x,
toByteOffset: vertexOffset,
as: Float.self)
vertexPointer.storeBytes(of: vertexWorldTransform.y,
toByteOffset: vertexOffset + componentStride,
as: Float.self)
vertexPointer.storeBytes(of: vertexWorldTransform.z,
toByteOffset: vertexOffset + (2 * componentStride),
as: Float.self)
}
let byteCountVertices = vertices.count * vertices.stride
let byteCountFaces = faces.count * faces.indexCountPerPrimitive * faces.bytesPerIndex
let vertexBuffer = allocator.newBuffer(with: Data(bytesNoCopy: vertexPointer,
count: byteCountVertices,
deallocator: .none), type: .vertex)
let indexBuffer = allocator.newBuffer(with: Data(bytesNoCopy: facePointer,
count: byteCountFaces,
deallocator: .none), type: .index)
let indexCount = faces.count * faces.indexCountPerPrimitive
let material = MDLMaterial(name: "material",
scatteringFunction: MDLPhysicallyPlausibleScatteringFunction())
let submesh = MDLSubmesh(indexBuffer: indexBuffer,
indexCount: indexCount,
indexType: .uInt32,
geometryType: .triangles,
material: material)
let vertexFormat = MTKModelIOVertexFormatFromMetal(vertices.format)
let vertexDescriptor = MDLVertexDescriptor()
vertexDescriptor.attributes[0] = MDLVertexAttribute(name: MDLVertexAttributePosition,
format: vertexFormat,
offset: 0,
bufferIndex: 0)
vertexDescriptor.layouts[0] = MDLVertexBufferLayout(stride: ma.geometry.vertices.stride)
let mesh = MDLMesh(vertexBuffer: vertexBuffer,
vertexCount: ma.geometry.vertices.count,
descriptor: vertexDescriptor,
submeshes: [submesh])
asset.add(mesh)
}
let filePath = FileManager.default.urls(for: .documentDirectory,
in: .userDomainMask).first!
let usd: URL = filePath.appendingPathComponent("model.usd")
if MDLAsset.canExportFileExtension("usd") {
do {
try asset.export(to: usd)
let controller = UIActivityViewController(activityItems: [usd],
applicationActivities: nil)
controller.popoverPresentationController?.sourceView = sender
self.present(controller, animated: true, completion: nil)
} catch let error {
fatalError(error.localizedDescription)
}
} else {
fatalError("Can't export USD")
}
}
点击 保存 按钮，在活动视图控制器中选择 更多 并通过 AirDrop 将准备好的模型发送到 Mac 的 下载 文件夹。
P.S.
在此处您可以找到有关 捕捉真实世界纹理 的额外信息。
- Andy Jazz
10
1你可以查看 @swiftcoder 的回答。在 ARMeshGeometry 的文档中甚至有示例代码。 - pkuhar
1需要写一些代码来实现它，并不意味着你不能做到。如果苹果公司将这些信息保留给自己，那么你可能会说NO，但在这种情况下并非如此。 - pkuhar
1你能给我们提供这个示例的git链接吗？我尝试运行这段代码时出现了“ARMeshGeometry类型的值没有成员'vertex'”的错误。 - yaali
1@AndyFedoroff 是的，看起来还不错，但我不喜欢网格本身的精度！我不知道是因为我使用的是2018年版的iPad Pro，还是所有设备都一样。 - Kawe
1非常好，它有效了！不知道为什么我之前没有尝试这个选项)) - Andy Jazz
显示剩余5条评论
0
我正在使用激光雷达进行3D扫描，但是我是初学者，请问如何使用Swift代码将其导出到以下文件格式：
- GLTF（在Android设备上共享AR）
- GLB
- STL（用于3D打印的非纹理文件）
- 点云（PCD PLY PTS XYZ LAS e57）
- 所有数据（包括捕获的图像）
- DAE（与Sketchfab兼容）
- FBX 谢谢
- Quach Tam
网页内容由stack overflow 提供, 点击上面的可以查看英文原文，
原文链接
原文链接
OBJ导出是否有效？我无法测试它，因为我没有带LiDAR扫描仪的iPad。 - Andy Jazz