如何用 realitykit 在多个点之间,画出一条圆的粗的贝塞尔曲线,按顺序,串联各个点
在 RealityKit 中绘制贝塞尔曲线并不是直接支持的功能,但你可以通过一些技巧来实现。你可以使用多个小的几何体(如球体或圆柱体)来近似绘制贝塞尔曲线。以下是一个基本的步骤指南:
定义贝塞尔曲线函数:首先,你需要定义一个函数来计算贝塞尔曲线上的点。对于三次贝塞尔曲线,你可以使用以下公式:
func bezierPoint(t: Float, p0: SIMD3<Float>, p1: SIMD3<Float>, p2: SIMD3<Float>, p3: SIMD3<Float>) -> SIMD3<Float> {
let u = 1 - t
let tt = t * t
let uu = u * u
let uuu = uu * u
let ttt = tt * t
var p = uuu * p0 // (1-t)^3 * p0
p += 3 * uu * t * p1 // 3 * (1-t)^2 * t * p1
p += 3 * u * tt * p2 // 3 * (1-t) * t^2 * p2
p += ttt * p3 // t^3 * p3
return p
}
生成贝塞尔曲线上的点:使用上述函数生成贝塞尔曲线上的多个点。
let p0 = SIMD3<Float>(0, 0, 0)
let p1 = SIMD3<Float>(1, 2, 0)
let p2 = SIMD3<Float>(2, 2, 0)
let p3 = SIMD3<Float>(3, 0, 0)
var points: [SIMD3<Float>] = []
let segments = 100
for i in 0...segments {
let t = Float(i) / Float(segments)
let point = bezierPoint(t: t, p0: p0, p1: p1, p2: p2, p3: p3)
points.append(point)
}
创建几何体:使用生成的点创建几何体来近似贝塞尔曲线。你可以使用球体或圆柱体来表示这些点。
import RealityKit
var entities: [Entity] = []
for point in points {
let sphere = MeshResource.generateSphere(radius: 0.01)
let material = SimpleMaterial(color: .blue, isMetallic: false)
let modelEntity = ModelEntity(mesh: sphere, materials: [material])
modelEntity.position = point
entities.append(modelEntity)
}
let anchorEntity = AnchorEntity(world: .zero)
for entity in entities {
anchorEntity.addChild(entity)
}
arView.scene.addAnchor(anchorEntity)
显示在 ARView 中:将这些几何体添加到 ARView 中的场景里。
import ARKit
import RealityKit
import SwiftUI
struct ContentView: View {
var body: some View {
ARViewContainer().edgesIgnoringSafeArea(.all)
}
}
struct ARViewContainer: UIViewRepresentable {
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
// 添加贝塞尔曲线
let p0 = SIMD3<Float>(0, 0, 0)
let p1 = SIMD3<Float>(1, 2, 0)
let p2 = SIMD3<Float>(2, 2, 0)
let p3 = SIMD3<Float>(3, 0, 0)
var points: [SIMD3<Float>] = []
let segments = 100
for i in 0...segments {
let t = Float(i) / Float(segments)
let point = bezierPoint(t: t, p0: p0, p1: p1, p2: p2, p3: p3)
points.append(point)
}
var entities: [Entity] = []
for point in points {
let sphere = MeshResource.generateSphere(radius: 0.01)
let material = SimpleMaterial(color: .blue, isMetallic: false)
let modelEntity = ModelEntity(mesh: sphere, materials: [material])
modelEntity.position = point
entities.append(modelEntity)
}
let anchorEntity = AnchorEntity(world: .zero)
for entity in entities {
anchorEntity.addChild(entity)
}
arView.scene.addAnchor(anchorEntity)
return arView
}
func updateUIView(_ uiView: ARView, context: Context) {}
}
@main
struct MyApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
通过这种方式,你可以在 RealityKit 中近似绘制贝塞尔曲线。虽然这种方法不是最优的,但它可以帮助你在 RealityKit 中实现贝塞尔曲线的可视化。