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// Maps HDR values to linear values
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// Based on http://www.oscars.org/science-technology/sci-tech-projects/aces
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fn aces_tone_map(hdr: vec3<f32>) -> vec3<f32> {
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let m1 = mat3x3(
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0.59719, 0.07600, 0.02840,
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0.35458, 0.90834, 0.13383,
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0.04823, 0.01566, 0.83777,
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);
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let m2 = mat3x3(
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1.60475, -0.10208, -0.00327,
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-0.53108, 1.10813, -0.07276,
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-0.07367, -0.00605, 1.07602,
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);
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let v = m1 * hdr;
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let a = v * (v + 0.0245786) - 0.000090537;
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let b = v * (0.983729 * v + 0.4329510) + 0.238081;
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return clamp(m2 * (a / b), vec3(0.0), vec3(1.0));
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}
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struct VertexOutput {
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@location(0) uv: vec2<f32>,
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@builtin(position) clip_position: vec4<f32>,
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};
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@vertex
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fn vs_main(
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@builtin(vertex_index) vi: u32,
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) -> VertexOutput {
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var out: VertexOutput;
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// Generate a triangle that covers the whole screen
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out.uv = vec2<f32>(
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f32((vi << 1u) & 2u),
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f32(vi & 2u),
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);
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out.clip_position = vec4<f32>(out.uv * 2.0 - 1.0, 0.0, 1.0);
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// We need to invert the y coordinate so the image
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// is not upside down
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out.uv.y = 1.0 - out.uv.y;
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return out;
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}
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@group(0)
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@binding(0)
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var hdr_image: texture_2d<f32>;
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@group(0)
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@binding(1)
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var hdr_sampler: sampler;
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@fragment
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fn fs_main(vs: VertexOutput) -> @location(0) vec4<f32> {
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let hdr = textureSample(hdr_image, hdr_sampler, vs.uv);
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let sdr = aces_tone_map(hdr.rgb);
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return vec4(sdr, hdr.a);
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}
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