visionOS空间计算实战开发教程Day 8 附属视图和动画

本节我们开始初探在visionOS中添加动画效果，我们的入口文件和??ContentView???和??Day 6???中并没有什么区别，所以重点来看??ViewModel???和??ImmersiveView??。

首先是??ViewModel.swift??文件：

import SwiftUI
import RealityKit

class ViewModel: ObservableObject {
    private var contentEntity = Entity()
    
    func setupContentEntity() -> Entity {
        return contentEntity
    }
    
    func getTargetEntity(name: String) -> Entity? {
        return contentEntity.children.first { $0.name == name }
    }
    
    func addCube(name: String, position: SIMD3<Float>, color: UIColor) -> ModelEntity {
        let entity = ModelEntity(
            mesh: .generateBox(size: 0.5, cornerRadius: 0),
            materials: [SimpleMaterial(color: color, isMetallic: false)],
            collisionShape: .generateBox(size: SIMD3<Float>(repeating: 0.5)),
            mass: 0.0
        )
        
        entity.name = name
        entity.position = position
        entity.components.set(InputTargetComponent(allowedInputTypes: .indirect))
        entity.components.set(CollisionComponent(shapes: [ShapeResource.generateBox(size: SIMD3<Float>(repeating: 0.5))], isStatic: true))
        entity.components.set(HoverEffectComponent())
        
        contentEntity.addChild(entity)
        
        return entity
    }
    
    func playAnimation(entity: Entity) {
        let goUp = FromToByAnimation<Transform>(
            name: "goUp",
            from: .init(scale: .init(repeating: 1), translation: entity.position),
            to: .init(scale: .init(repeating: 1), translation: entity.position + .init(x:0 ,y: 0.4, z: 0)),
            duration: 0.2,
            timing: .easeOut,
            bindTarget: .transform
        )
        
        let pause = FromToByAnimation<Transform>(
            name: "pause",
            from: .init(scale: .init(repeating: 1), translation: entity.position + .init(x:0 ,y: 0.4, z: 0)),
            to: .init(scale: .init(repeating: 1), translation: entity.position + .init(x:0 ,y: 0.4, z: 0)),
            duration: 0.1,
            bindTarget: .transform
        )
        
        let goDown = FromToByAnimation<Transform>(
            name: "goDown",
            from: .init(scale: .init(repeating: 1), translation: entity.position + .init(x:0 ,y: 0.4, z: 0)),
            to: .init(scale: .init(repeating: 1), translation: entity.position),
            duration: 0.2,
            timing: .easeOut,
            bindTarget: .transform
        )
        
        let goUpAnimation = try! AnimationResource.generate(with: goUp)
        
        let pauseAnimation = try! AnimationResource.generate(with: pause)
        
        let goDownAnimation = try! AnimationResource.generate(with: goDown)
        
        let animation = try! AnimationResource.sequence(with: [goUpAnimation, pauseAnimation, goDownAnimation])
        
        entity.playAnimation(animation, transitionDuration: 0.5)
    }
}

通过前面的学习我们已经知道??setupContentEntity???用于初始化实体对象，??getTargetEntity???用于根据模型的名称查找到指定模型。??addCube(name: String, position: SIMD3<Float>, color: UIColor)???中包含三个参数，??name???用于指定所创建盒子的名称，??position???用于指定盒子所处的位置，同样是按人所处位置为参照坐标，??color??用于指定盒体的颜色。

接下来就是本节的一个重要的知识点了，??playAnimation???用于创建动画效果，传入的参数??entity??就是要实现动画效果的模型。

结构体??FromToByAnimation???可用于实现实体对象和场景的动画，方式为逐渐修改参数值。??from???值表示动画属性的起始值，??to???表示动画结束时的属性值，也可以通过??by???值让框架来计算动画结束时的值。??duration???顾名思义是指动画的时长，??timing???参数通过??AnimationTimingFunction??结构体中的定时函数进行指定，包含的值有：

• default：生成默认过渡曲线的定时函数，不指定时此即为默认值。
• linear：生成线性过渡效果的定时函数。
• easeIn：生成淡入效果的定时函数。
• easeOut：生成淡出效果的定时函数。
• easeInOut：生成淡入淡出效果的定时函数。

??bindTarget???参数指定为??tranform??时表示动画作用于对象本身。

我们定义了三个动画函数，分别为??goUp???、??pause???和??goDown???，实现在纵坐标上完成上下移动0.4个单位的动画效果。接下来通过这三个动画定义来生成动画资源并指定动画的顺序，最后对实体对象调用??playAnimation???来播放动画，这里的??transitionDuration??参数与三个动画函数中用时的总和相同。

接下来是我们的??ImmersiveView??:

import SwiftUI
import RealityKit

struct ImmersiveView: View {
    @State var model = ViewModel()
    @State var cube1 = ModelEntity()
    @State var cube2 = ModelEntity()
        
    var body: some View {
        RealityView { content, attachments in
            content.add(model.setupContentEntity())
            cube1 = model.addCube(name: "Cube1", position: SIMD3<Float>(x: 1, y: 1, z: -2), color: .red)
            cube2 = model.addCube(name: "Cube2", position: SIMD3<Float>(x: -1, y: 1, z: -2), color: .blue)
            
            if let attachment = attachments.entity(for: "cube1_label") {
                attachment.position = [0, -0.35, 0]
                cube1.addChild(attachment)
            }
            
            if let attachment = attachments.entity(for: "cube2_label") {
                attachment.position = [0, -0.35, 0]
                cube2.addChild(attachment)
            }
        } attachments: {
            Attachment(id: "cube1_label") {
                Text("Cube1")
                    .font(.system(size: 48))
            }
            Attachment(id: "cube2_label") {
                Text("Cube2")
                    .font(.system(size: 48))
            }
        }
        .gesture(
            SpatialTapGesture()
                .targetedToEntity(cube1)
                .onEnded { value in
                    print(value)
                    model.playAnimation(entity: cube1)
                }
        )
        .gesture(
            SpatialTapGesture()
                .targetedToEntity(cube2)
                .onEnded { value in
                    print(value)
                    model.playAnimation(entity: cube2)
                }
        )
    }
}

??cube1???为红色，位于我们的右侧，??cube2???为蓝色，位于我们的左侧，为方便标识，我们通过??RealityView???的??AttachmentContentBuilder???（即??attachments???参数）来创建附属视图，但附属视图并不会自动添加到??RealityView???的对象上。我们需要显式地进行指定，这里??attachments.entity???中的??for???与??Attachment???的??id???相对应，我们只添加了两个文本视图，并通过??position??指定了相对于父对象的位置。

接着通过??SpatialTapGesture???指定在点击相应盒子时执行前面所定义的??playAnimation??。

运行应用，点击??Show ImmersiveSpace??会显示两个盒子，盒子下方分别显示一个附属视图，点击盒体会执行上下移动的动画。

示例代码：??GitHub仓库??

其它相关内容请见??虚拟现实(VR)/增强现实(AR)&visionOS开发学习笔记??