Ios Swift在SceneKit中为scnnode添加自定义几何体(视图)

要使用自定义SwiftUI视图作为SceneKit中SCNNode的几何体，可以从将SwiftUI视图渲染为UIImage开始.这可以通过创建视图的快照来完成.

Once you have the UIImage, you can apply it as a texture to the SCNMaterial of your SCNNode.
See for instance "Updating SCNMaterial texture in SceneKit" from Benoit Layer.

最后，创建一个geometry(例如，SCNPlane)，并将具有自定义纹理的material 应用于此几何体.

这一过程将是:

[ SwiftUI View ]
    │
    ├─ Render to UIImage
    │
[ UIImage ]
    │
    ├─ Apply as Texture to Material
    │
[ SCNMaterial ]
    │
    ├─ Attach to SCNPlane or other geometry
    │
[ SCNNode ]

您的SwiftUI View to UIImage将是:

import SwiftUI

extension View {
    func snapshot() -> UIImage {
        let controller = UIHostingController(rootView: self)
        let view = controller.view

        let targetSize = controller.view.intrinsicContentSize
        view?.bounds = CGRect(x: 0, y: 0, width: targetSize.width, height: targetSize.height)
        view?.backgroundColor = .clear

        let renderer = UIGraphicsImageRenderer(size: targetSize)
        return renderer.image { _ in
            view?.drawHierarchy(in: controller.view.bounds, afterScreenUpdates: true)
        }
    }
}

然后应用自定义几何体:

import SceneKit
import SwiftUI

// Example SwiftUI View
struct CustomView: View {
    var body: some View {
        Text("Hello World")
            .frame(width: 100, height: 100)
            .background(Color.red)
    }
}

// Convert SwiftUI view to UIImage
let image = CustomView().snapshot()

// Create material with this image
let material = SCNMaterial()
material.diffuse.contents = image

// Create a geometry, e.g., SCNPlane
let plane = SCNPlane(width: 1.0, height: 1.0)
plane.materials = [material]

// Create a SCNNode with this geometry
let customNode = SCNNode(geometry: plane)

// Position and add the custom node as needed
customNode.position = SCNVector3(x: 0, y: 0, z: 0)
dotNode.addChildNode(customNode)

但是:SwiftUI视图呈现为静态图像，因此它们在SceneKit上下文中不是交互式的.

警告=== AttributeGraph: cycle detected through attribute 1517200 ===表示SwiftUI中存在循环依赖或与视图布局相关的问题.当视图的状态发生变化，导致SwiftUI不断重新计算视图的布局，从而导致无限循环时，就会发生这种情况.

所以试着简化SwiftUI视图:暂时用一个非常简单的视图(比如一个Text元素)替换SwiftUI视图，以确认是否是视图的复杂性导致了问题.

并确保您没有使用任何可能导致循环依赖的视图修改器，例如那些依赖于视图自身大小或布局的修改器.在将SwiftUI视图渲染为UIImage之前，为其设置明确的帧大小.这有助于防止与可能导致循环的大小计算相关的问题.

extension View {
    func snapshot() -> UIImage {
        let controller = UIHostingController(rootView: self.frame(width: 100, height: 100))
        let view = controller.view

        let targetSize = CGSize(width: 100, height: 100)
        view?.bounds = CGRect(origin: .zero, size: targetSize)
        view?.backgroundColor = .clear

        let renderer = UIGraphicsImageRenderer(size: targetSize)
        return renderer.image { _ in
            view?.drawHierarchy(in: CGRect(origin: .zero, size: targetSize), afterScreenUpdates: true)
        }
    }
}

确保在主线程上执行所有与UI相关的任务，包括将SwiftUI视图呈现为UIImage.

DispatchQueue.main.async {
    let image = CustomView().snapshot()

    // Create material with this image
    let material = SCNMaterial()
    material.diffuse.contents = image

    // Rest of the code to create and add SCNNode
    // 
}