88 lines
3.1 KiB
WebGPU Shading Language
88 lines
3.1 KiB
WebGPU Shading Language
#import bevy_pbr::{
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mesh_view_bindings::globals,
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forward_io::VertexOutput,
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}
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@group(2) @binding(0) var<uniform> ring_radius: f32;
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@group(2) @binding(1) var<uniform> jupiter_radius: f32;
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const jupiter_radius_Mm: f32 = 71.492;
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const brightness = 0.025;
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fn smooth_edge(start: f32, end: f32, value: f32) -> f32 {
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var x: f32 = (value - start) / (end - start);
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return 4 * x * x * (1 - x * x);
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}
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fn ring_density(radius: f32) -> f32 {
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// NOTE: Keep this in sync with src/nature.rs::ring_density
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// Input: distance to center of jupiter in million meters
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// Output: relative brightness of the ring
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let halo_inner: f32 = 92.0;
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let halo_outer: f32 = 122.5;
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let main_inner: f32 = 122.5;
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let main_outer: f32 = 129.0;
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let amalthea_inner: f32 = 129.0;
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let amalthea_outer: f32 = 182.0;
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let thebe_inner: f32 = 129.0;
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let thebe_outer: f32 = 229.0;
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let metis_notch_center: f32 = 128.0;
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let metis_notch_width: f32 = 0.6;
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let halo_brightness: f32 = 0.75;
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let main_brightness: f32 = 1.0;
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let almathea_brightness: f32 = 0.5;
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let thebe_brightness: f32 = 0.5;
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var density: f32 = 0.0;
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if (radius >= halo_inner && radius <= halo_outer) {
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density = halo_brightness * smooth_edge(halo_inner, halo_outer, radius);
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} else if (radius >= main_inner && radius <= main_outer) {
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var metis_notch_effect: f32 = 1.0;
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if (radius > metis_notch_center - metis_notch_width * 0.5 && radius < metis_notch_center + metis_notch_width * 0.5) {
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metis_notch_effect = 0.5 * (1.0 - smooth_edge(metis_notch_center - metis_notch_width * 0.5, metis_notch_center + metis_notch_width * 0.5, radius));
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}
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density = main_brightness * metis_notch_effect * smooth_edge(main_inner, main_outer, radius);
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} else {
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if (radius >= amalthea_inner && radius <= amalthea_outer) {
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density = almathea_brightness * smooth_edge(amalthea_inner, amalthea_outer, radius);
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}
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if (radius >= thebe_inner && radius <= thebe_outer) {
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density += thebe_brightness * smooth_edge(thebe_inner, thebe_outer, radius);
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}
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}
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return density;
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}
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@fragment
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fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
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let jupiter_percent = jupiter_radius / ring_radius;
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let color = vec3<f32>(0.3, 0.3, 0.3);
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var alpha = brightness;
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let r_uv = 2 * distance(in.uv, vec2<f32>(0.5));
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let r = r_uv * ring_radius / jupiter_radius * jupiter_radius_Mm;
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alpha *= ring_density(r);
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alpha -= 0.001;
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if alpha <= 0.0 {
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return vec4<f32>(color, 0.0);
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}
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if in.uv[0] < 0.5 {
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let dist = (0.5 - in.uv[0]) * 2.0; // 0.0=jupiter's center, 1.0=edge of the ring
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let side_dist = abs(in.uv[1] - 0.5);
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let cutoff = 0.5 * jupiter_percent * cos(dist);
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if side_dist < cutoff {
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return vec4<f32>(color, 0.0);
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}
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let fuzzy_boundary = 0.01;
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if side_dist < cutoff + fuzzy_boundary {
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return vec4<f32>(color, alpha * (side_dist - cutoff) / fuzzy_boundary);
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}
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}
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return vec4<f32>(color, alpha);
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}
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