Swift RealityKit如何获得两个相对大小相同的ModelEntity

如果您想要根据文本位置自动计算黑框(文本板)的大小和位置，请try 此代码:

import SwiftUI
import RealityKit

struct ContentView: View {
    let sample = "This is the text on the screen"
    let mat = SimpleMaterial(color: .red, roughness: 0.7, isMetallic: true)
    let headAnchor = AnchorEntity(.head)

    init() {
        headAnchor.anchoring.trackingMode = .once
    }
    var body: some View {
        RealityView { content in
            // Text
            let textModel = await getText(sample)
            let xPos = textModel.visualBounds(relativeTo: nil).extents.x / 2
            textModel.position = [-xPos, -1.25, -0.75]
            textModel.setParent(headAnchor)
            // Text BB Center
            let bb_Center = textModel.visualBounds(relativeTo: nil).center
            let x = bb_Center.x
            let y = bb_Center.y
            let z = bb_Center.z
            // Text BB Extents
            let bb_Extents = textModel.visualBounds(relativeTo: nil).extents
            let xE = bb_Extents.x
            let yE = bb_Extents.y
            let zE = bb_Extents.z
            // Black box
            let blackBoxModel = ModelEntity(
                                        mesh: .generateBox(size: [xE+0.3, yE+0.2, zE],
                                cornerRadius: 0.1),
                                   materials: [UnlitMaterial(color: .black)]
            )
            blackBoxModel.position = [x, y-0.02, z-0.05]
            blackBoxModel.setParent(headAnchor)
            content.add(headAnchor)
        }
    }
    
    func getText(_ newText: String) async -> ModelEntity {
        let depthVar: Float = 0.01
        let fontVar = UIFont.systemFont(ofSize: 0.1)
        let containerFrameVar = CGRect(x: 0, y: 0, width: 1, height: 1)
        let alignmentVar: CTTextAlignment = .center
        let lineBreakModeVar : CTLineBreakMode = .byWordWrapping
        
        let model: ModelEntity = await ModelEntity(
                                              mesh: .generateText(newText,
                                    extrusionDepth: depthVar,
                                              font: fontVar,
                                    containerFrame: containerFrameVar,
                                         alignment: alignmentVar,
                                     lineBreakMode: lineBreakModeVar),
                                         materials: [mat]
        )
        await model.components.set(InputTargetComponent())
        await model.generateCollisionShapes(recursive: false)
        await model.components.set(HoverEffectComponent())
        return model
    }
}