// Vertex shader bindings
struct VertexOutput {
@location(0) tex_coord: vec2<f32>,
@location(1) color: vec4<f32>, // gamma 0-1
@builtin(position) position: vec4<f32>,
};
struct Locals {
screen_size: vec2<f32>,
/// 1 if dithering is enabled, 0 otherwise
dithering: u32,
/// 1 to do manual filtering for more predictable kittest snapshot images.
/// See also https://github.com/emilk/egui/issues/5295
predictable_texture_filtering: u32,
};
@group(0) @binding(0) var<uniform> r_locals: Locals;
// -----------------------------------------------
// Adapted from
// https://www.shadertoy.com/view/llVGzG
// Originally presented in:
// Jimenez 2014, "Next Generation Post-Processing in Call of Duty"
//
// A good overview can be found in
// https://blog.demofox.org/2022/01/01/interleaved-gradient-noise-a-different-kind-of-low-discrepancy-sequence/
// via https://github.com/rerun-io/rerun/
fn interleaved_gradient_noise(n: vec2<f32>) -> f32 {
let f = 0.06711056 * n.x + 0.00583715 * n.y;
return fract(52.9829189 * fract(f));
}
fn dither_interleaved(rgb: vec3<f32>, levels: f32, frag_coord: vec4<f32>) -> vec3<f32> {
var noise = interleaved_gradient_noise(frag_coord.xy);
// scale down the noise slightly to ensure flat colors aren't getting dithered
noise = (noise - 0.5) * 0.95;
return rgb + noise / (levels - 1.0);
}
// 0-1 linear from 0-1 sRGB gamma
fn linear_from_gamma_rgb(srgb: vec3<f32>) -> vec3<f32> {
let cutoff = srgb < vec3<f32>(0.04045);
let lower = srgb / vec3<f32>(12.92);
let higher = pow((srgb + vec3<f32>(0.055)) / vec3<f32>(1.055), vec3<f32>(2.4));
return select(higher, lower, cutoff);
}
// 0-1 sRGB gamma from 0-1 linear
fn gamma_from_linear_rgb(rgb: vec3<f32>) -> vec3<f32> {
let cutoff = rgb < vec3<f32>(0.0031308);
let lower = rgb * vec3<f32>(12.92);
let higher = vec3<f32>(1.055) * pow(rgb, vec3<f32>(1.0 / 2.4)) - vec3<f32>(0.055);
return select(higher, lower, cutoff);
}
// 0-1 sRGBA gamma from 0-1 linear
fn gamma_from_linear_rgba(linear_rgba: vec4<f32>) -> vec4<f32> {
return vec4<f32>(gamma_from_linear_rgb(linear_rgba.rgb), linear_rgba.a);
}
// [u8; 4] SRGB as u32 -> [r, g, b, a] in 0.-1
fn unpack_color(color: u32) -> vec4<f32> {
return vec4<f32>(
f32(color & 255u),
f32((color >> 8u) & 255u),
f32((color >> 16u) & 255u),
f32((color >> 24u) & 255u),
) / 255.0;
}
fn position_from_screen(screen_pos: vec2<f32>) -> vec4<f32> {
return vec4<f32>(
2.0 * screen_pos.x / r_locals.screen_size.x - 1.0,
1.0 - 2.0 * screen_pos.y / r_locals.screen_size.y,
0.0,
1.0,
);
}
@vertex
fn vs_main(
@location(0) a_pos: vec2<f32>,
@location(1) a_tex_coord: vec2<f32>,
@location(2) a_color: u32,
) -> VertexOutput {
var out: VertexOutput;
out.tex_coord = a_tex_coord;
out.color = unpack_color(a_color);
out.position = position_from_screen(a_pos);
return out;
}
// Fragment shader bindings
@group(1) @binding(0) var r_tex_color: texture_2d<f32>;
@group(1) @binding(1) var r_tex_sampler: sampler;
fn sample_texture(in: VertexOutput) -> vec4<f32> {
if r_locals.predictable_texture_filtering == 0 {
// Hardware filtering: fast, but varies across GPUs and drivers.
return textureSample(r_tex_color, r_tex_sampler, in.tex_coord);
} else {
// Manual bilinear filtering with four taps at pixel centers using textureLoad
let texture_size = vec2<i32>(textureDimensions(r_tex_color, 0));
let texture_size_f = vec2<f32>(texture_size);
let pixel_coord = in.tex_coord * texture_size_f - 0.5;
let pixel_fract = fract(pixel_coord);
let pixel_floor = vec2<i32>(floor(pixel_coord));
// Manual texture clamping
let max_coord = texture_size - vec2<i32>(1, 1);
let p00 = clamp(pixel_floor + vec2<i32>(0, 0), vec2<i32>(0, 0), max_coord);
let p10 = clamp(pixel_floor + vec2<i32>(1, 0), vec2<i32>(0, 0), max_coord);
let p01 = clamp(pixel_floor + vec2<i32>(0, 1), vec2<i32>(0, 0), max_coord);
let p11 = clamp(pixel_floor + vec2<i32>(1, 1), vec2<i32>(0, 0), max_coord);
// Load at pixel centers
let tl = textureLoad(r_tex_color, p00, 0);
let tr = textureLoad(r_tex_color, p10, 0);
let bl = textureLoad(r_tex_color, p01, 0);
let br = textureLoad(r_tex_color, p11, 0);
// Manual bilinear interpolation
let top = mix(tl, tr, pixel_fract.x);
let bottom = mix(bl, br, pixel_fract.x);
return mix(top, bottom, pixel_fract.y);
}
}
@fragment
fn fs_main_linear_framebuffer(in: VertexOutput) -> @location(0) vec4<f32> {
// We expect "normal" textures that are NOT sRGB-aware.
let tex_gamma = sample_texture(in);
var out_color_gamma = in.color * tex_gamma;
// Dither the float color down to eight bits to reduce banding.
// This step is optional for egui backends.
// Note that dithering is performed on the gamma encoded values,
// because this function is used together with a srgb converting target.
if r_locals.dithering == 1 {
let out_color_gamma_rgb = dither_interleaved(out_color_gamma.rgb, 256.0, in.position);
out_color_gamma = vec4<f32>(out_color_gamma_rgb, out_color_gamma.a);
}
let out_color_linear = linear_from_gamma_rgb(out_color_gamma.rgb);
return vec4<f32>(out_color_linear, out_color_gamma.a);
}
@fragment
fn fs_main_gamma_framebuffer(in: VertexOutput) -> @location(0) vec4<f32> {
// We expect "normal" textures that are NOT sRGB-aware.
let tex_gamma = sample_texture(in);
var out_color_gamma = in.color * tex_gamma;
// Dither the float color down to eight bits to reduce banding.
// This step is optional for egui backends.
if r_locals.dithering == 1 {
let out_color_gamma_rgb = dither_interleaved(out_color_gamma.rgb, 256.0, in.position);
out_color_gamma = vec4<f32>(out_color_gamma_rgb, out_color_gamma.a);
}
return out_color_gamma;
}