How do I create a view with custom shader?

To create a view with a custom shader in SwiftUI, you can follow these steps:

1. Instantiate a Shader: You start by calling a function with the shader's name on the shader library. You can also pass additional parameters to your shader function, such as colors, numbers, or images.

2. Apply the Shader to a View: Use the layerEffect view modifier to apply the shader to a view. SwiftUI will call your shader function for every pixel of your view, running the shader on the GPU for real-time performance.

3. Write the Shader in Metal: Shaders are written in the Metal shading language. The shader function in Metal should match the invocation on the shader library in SwiftUI. The function will be executed on the GPU for each pixel of your view.

4. Create a View Modifier: To call the shader function from SwiftUI, create a view modifier that exposes all the parameters of the shader function to SwiftUI. This modifier will instantiate the shader and apply it to its content.

5. Drive the Animation: Since shaders have no concept of time, you need to drive the animation from SwiftUI. You can use a view modifier like keyframeAnimator to run animations based on external changes like gestures.

Here is a brief example based on the context provided:

// SwiftUI code to instantiate and apply the shader
struct RippleModifier: ViewModifier {
    var time: Float
    var origin: CGPoint

    func body(content: Content) -> some View {
        content
            .layerEffect(ShaderLibrary.ripple(time: time, origin: origin), maxSampleOffset: .zero)
    }
}

// Metal shader function
#include <metal_stdlib>
using namespace metal;

half4 ripple(float2 position [[position]], float2 origin, float time) {
    float dist = distance(position, origin);
    float ripple = sin(dist - time * 10.0) * 0.1;
    return half4(ripple, ripple, ripple, 1.0);
}

For more detailed steps and examples, you can refer to the session Create custom visual effects with SwiftUI.

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