1// The vignette postprocessing effect.
2
3#define_import_path bevy_post_process::effect_stack::vignette
4
5#import bevy_post_process::effect_stack::chromatic_aberration::source_texture
6
7// See `bevy_post_process::effect_stack::Vignette` for more
8// information on these fields.
9struct VignetteSettings {
10    intensity: f32,
11    radius: f32,
12    smoothness: f32,
13    roundness: f32,
14    center: vec2<f32>,
15    edge_compensation: f32,
16    unused: u32,
17    color: vec4<f32>
18}
19
20const VISUAL_THRESHOLD: f32 = 1e-4;
21
22// The settings supplied by the developer.
23@group(0) @binding(4) var<uniform> vignette_settings: VignetteSettings;
24
25fn vignette(uv: vec2<f32>, color: vec3<f32>) -> vec3<f32> {
26    let intensity = vignette_settings.intensity;
27    if (intensity < VISUAL_THRESHOLD) {
28        return color;
29    }
30    let radius = vignette_settings.radius;
31    let smoothness = vignette_settings.smoothness;
32    let roundness = vignette_settings.roundness;
33    let edge_comp = vignette_settings.edge_compensation;
34
35    // Get the screen resolution.
36    let dims = textureDimensions(source_texture);
37    let resolution = vec2<f32>(dims.xy);
38    let screen_aspect = resolution.x / resolution.y;
39
40    // Calculate the aspect ratio.
41    //
42    // We divide by the smallest dimension to normalize the scale.
43    // This will be used later to force the vignette to be circular, not oval.
44    let aspect_ratio = resolution / min(resolution.x, resolution.y);
45
46    // Center the UV coordinates at (0,0).
47    let centered_uv = uv - 0.5;
48
49    // Calculate the normalized offset from the center.
50    //
51    // (vignette_settings.center - 0.5) maps the 0.0-1.0 input to -0.5-0.5.
52    // Multiplying by (1.0, y/x) compensates for the screen's aspect ratio.
53    // This ensures that a movement of 0.1 looks the same distance horizontally and vertically.
54    let offset = (vignette_settings.center - 0.5) * vec2<f32>(1.0, resolution.y / resolution.x);
55
56    let uv_from_center = centered_uv - offset;
57    var scale_vec = aspect_ratio * vec2<f32>(1.0, 1.0 / roundness);
58
59    // Apply edge compensation to make the vignette fit the screen better.
60    if (screen_aspect >= 1.0) {
61        let compensation_factor = mix(1.0, 1.0 / screen_aspect, edge_comp);
62        scale_vec.x *= compensation_factor;
63    } else {
64        let compensation_factor = mix(1.0, screen_aspect, edge_comp);
65        scale_vec.y *= compensation_factor;
66    }
67
68    let final_uv = uv_from_center * scale_vec;
69
70    // Calculate distance from center.
71    let dist = length(final_uv) * (1.0 / radius);
72    let base_curve = 1.0 - (dist * dist);
73    let clamped_factor = clamp(base_curve, 0.0, 1.0);
74    let factor = pow(clamped_factor, smoothness);
75
76    // Blend the original color with the vignette color.
77    return mix(color, vignette_settings.color.rgb, (1.0 - factor) * intensity);
78}