// Circle mask compute shader
// Generates a circular mask (1.0 inside, 0.0 outside)

struct Uniforms {
  radius: f32,
  aspect_ratio: f32,
  width: f32,
  height: f32,
};

@group(0) @binding(0) var<uniform> uniforms: Uniforms;

struct VSOutput {
  @builtin(position) position: vec4<f32>,
};

@vertex fn vs_main(@builtin(vertex_index) i: u32) -> VSOutput {
  var pos = array<vec2<f32>, 3>(
    vec2<f32>(-1, -1), vec2<f32>(3, -1), vec2<f32>(-1, 3));
  return VSOutput(vec4<f32>(pos[i], 0.0, 1.0));
}

@fragment fn fs_main(@builtin(position) p: vec4<f32>) -> @location(0) vec4<f32> {
  let uv = p.xy / vec2<f32>(uniforms.width, uniforms.height);
  let center = vec2<f32>(0.5, 0.5);
  let aspect_corrected_uv = (uv - center) * vec2<f32>(uniforms.aspect_ratio, 1.0);
  let dist = length(aspect_corrected_uv);

  let edge_width = 0.01;
  let mask = smoothstep(uniforms.radius + edge_width, uniforms.radius - edge_width, dist);

  return vec4<f32>(mask, mask, mask, 1.0);
}