struct Params {
	divisor: f32,
}

struct Vertex {
	@location(0) screen: vec2f,
}

struct Varying {
	@location(0) tex: vec2f,
	@builtin(position) v: vec4f,
}

@group(0) @binding(0) var smp: sampler;
@group(0) @binding(1) var tex: texture_2d<f32>;
@group(0) @binding(2) var<uniform> params: Params;

@vertex
fn on_vertex(in: Vertex) -> Varying {
	let uv = in.screen;
	let xy = vec2(2. * uv.x - 1., 1. - 2. * uv.y);
	return Varying(uv, vec4(xy, 0., 1.));
}

@fragment
fn on_fragment(in: Varying) -> @location(0) vec4f {
	let pixel = textureSample(tex, smp, in.tex) / params.divisor;
	return vec4(rational_tone_map(pixel.xyz), 1.0);
}

fn rational_tone_map(hdr: vec3<f32>) -> vec3<f32> {
	let luminosity = dot(hdr, vec3(0.2126, 0.7152, 0.0722));
	let color = hdr / luminosity;
	let luma = luminosity / (luminosity + 1.0);
	return luma * color;
}