simpledistortion.metal

#include <metal_stdlib>
#include <SwiftUI/SwiftUI.h>
using namespace metal;

[[ stitchable ]] half4 simpledistort(float2 pos, SwiftUI::Layer l, float4 boundingRect, float progress, float distortion) {
    
    float2 size = boundingRect.zw;
    float2 uv = pos / size;
    float2 center = float2(0.5, 0.5);
    float2 delta = uv - center;
    
    float distance = length(delta);
    
    //Creating Liquid Circle-esque distortion
    float outsideMask = smoothstep(distortion, 0.51, distance);
    //Inner distortion
    float2 ripple = float2(sin(delta.x * 3), cos(delta.y * 3));
    
    float2 newpos = uv;
    newpos -= ripple * distortion;
    newpos += pow(outsideMask,2.0);
    
    half4 color = l.sample(newpos * size);
    
    //Blocking out pixels outside of radius
    float holeMask = 1.0 - step(0.5, distance);
    color *= holeMask;

    return color;
}