// This file is part of the 64k demo project.
// GPU composite shader: Blend two textures.

struct BlendParams {
  width: u32,
  height: u32,
  blend_factor: f32,
  _pad0: f32,
}

@group(0) @binding(0) var output_tex: texture_storage_2d<rgba8unorm, write>;
@group(0) @binding(1) var<uniform> params: BlendParams;
@group(0) @binding(2) var input_a: texture_2d<f32>;
@group(0) @binding(3) var input_b: texture_2d<f32>;
@group(0) @binding(4) var tex_sampler: sampler;

@compute @workgroup_size(8, 8, 1)
fn main(@builtin(global_invocation_id) id: vec3<u32>) {
  if (id.x >= params.width || id.y >= params.height) { return; }

  let uv = vec2<f32>(f32(id.x) / f32(params.width),
                      f32(id.y) / f32(params.height));

  let color_a = textureSampleLevel(input_a, tex_sampler, uv, 0.0);
  let color_b = textureSampleLevel(input_b, tex_sampler, uv, 0.0);
  let blended = mix(color_a, color_b, params.blend_factor);

  textureStore(output_tex, id.xy, blended);
}