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How to create 3D effects like Cover Flow using ScrollView and GeometryReader

Paul Hudson    @twostraws   

Updated for Xcode 13.0 beta 2

If we combine GeometryReader with any view that can change position – such as something that has a drag gestures or is inside a List – we can create 3D effects that look great on the screen. GeometryReader allows us to read the coordinates for a view, and feed those values directly into a rotation3DEffect() modifier.

For example, we could create a Cover Flow-style scrolling effect by stacking up many text views horizontally in a scroll view, then applying rotation3DEffect() so that as they move in the scroll view they gently spin around, like this:

ScrollView(.horizontal, showsIndicators: false) {
    HStack(spacing: 0) {
        ForEach(1..<20) { num in
            VStack {
                GeometryReader { geo in
                    Text("Number \(num)")
                        .font(.largeTitle)
                        .padding()
                        .background(Color.red)
                        .rotation3DEffect(.degrees(-Double(geo.frame(in: .global).minX) / 8), axis: (x: 0, y: 1, z: 0))
                        .frame(width: 200, height: 200)
                }
                .frame(width: 200, height: 200)
            }
        }
    }
}

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You don’t always need to use GeometryReader to get interesting effects like – you could something similar with a DragGesture(), for example. So, this code creates a card-like rectangle that can be dragged around in both X and Y axes, and uses two rotation3DEffect() modifiers to apply values from that drag:

struct ContentView: View {
    @State var dragAmount = CGSize.zero

    var body: some View {
        VStack {
            Rectangle()
                .fill(LinearGradient(gradient: Gradient(colors: [.yellow, .red]), startPoint: .topLeading, endPoint: .bottomTrailing))
                .frame(width: 200, height: 150)
                .clipShape(RoundedRectangle(cornerRadius: 20))
                .rotation3DEffect(.degrees(-Double(dragAmount.width) / 20), axis: (x: 0, y: 1, z: 0))
                .rotation3DEffect(.degrees(Double(dragAmount.height / 20)), axis: (x: 1, y: 0, z: 0))
                .offset(dragAmount)
                .gesture(
                    DragGesture()
                        .onChanged { dragAmount = $0.translation }
                        .onEnded { _ in
                            withAnimation(.spring()) {
                                dragAmount = .zero
                            }
                        }
                )
        }
        .frame(width: 400, height: 400)
    }
}

Download this as an Xcode project

As you drag the card around you’ll see it rotates to give a perspective effect.

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