ARKit 3.5 –如何使用LiDAR从新的iPad Pro导出OBJ? [英] ARKit 3.5 – How to export OBJ from new iPad Pro with LiDAR?

问题描述

如何将最新iPad Pro上新的SceneReconstruction API生成的ARMeshGeometry导出到.obj文件?

How can I export the ARMeshGeometry generated by the new SceneReconstruction API on the latest iPad Pro to an .obj file?

这是场景重建文档.

推荐答案

从Apple的可视化开始Scene Scemantics 示例应用程序，您可以从第一个锚点检索 ARMeshGeometry 对象在框架中.

Starting with Apple's Visualising Scene Scemantics sample app, you can retrieve the ARMeshGeometry object from the first anchor in the frame.

导出数据的最简单方法是先将其转换为MDLMesh:

The easiest approach to exporting the data is to first convert it to an 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]);
    }
}

拥有MDLMesh之后，轻而易举地导出到OBJ文件:

Once you have the MDLMesh, exporting to an OBJ file is a breeze:

    @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");
            }
        }
    }

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