From e579ae120290329fd697b50ea9138ffccb65a805 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Wed, 1 Apr 2026 13:57:32 +0200
Subject: feat: migrate GPU renderer from WebGL to wgpu/WASM

---
 rust/crates/gpu/src/shaders/jfa_distance.wgsl | 50 +++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 rust/crates/gpu/src/shaders/jfa_distance.wgsl

(limited to 'rust/crates/gpu/src/shaders/jfa_distance.wgsl')

diff --git a/rust/crates/gpu/src/shaders/jfa_distance.wgsl b/rust/crates/gpu/src/shaders/jfa_distance.wgsl
new file mode 100644
index 00000000..e65a7023
--- /dev/null
+++ b/rust/crates/gpu/src/shaders/jfa_distance.wgsl
@@ -0,0 +1,50 @@
+struct VertexOutput {
+    @builtin(position) position: vec4f,
+    @location(0) tex_coord: vec2f,
+}
+
+struct DistanceUniforms {
+    resolution: vec2f,
+    feather_half: f32,
+    _padding: f32,
+}
+
+@group(0) @binding(0) var inside_texture: texture_2d<f32>;
+@group(0) @binding(1) var inside_sampler: sampler;
+@group(1) @binding(0) var outside_texture: texture_2d<f32>;
+@group(1) @binding(1) var outside_sampler: sampler;
+@group(2) @binding(0) var<uniform> uniforms: DistanceUniforms;
+
+fn decode_seed(encoded: vec4f) -> vec2f {
+    let x = floor(encoded.r * 255.0 + 0.5) * 256.0 + floor(encoded.g * 255.0 + 0.5);
+    let y = floor(encoded.b * 255.0 + 0.5) * 256.0 + floor(encoded.a * 255.0 + 0.5);
+    return vec2f(x, y);
+}
+
+fn is_no_seed(encoded: vec4f) -> bool {
+    return encoded.r > 0.99 && encoded.g > 0.99 && encoded.b > 0.99 && encoded.a > 0.99;
+}
+
+@fragment
+fn fragment_main(input: VertexOutput) -> @location(0) vec4f {
+    let pixel_coord = floor(input.tex_coord * uniforms.resolution);
+    let inside_encoded = textureSample(inside_texture, inside_sampler, input.tex_coord);
+    let outside_encoded = textureSample(outside_texture, outside_sampler, input.tex_coord);
+
+    let has_inside = !is_no_seed(inside_encoded);
+    let has_outside = !is_no_seed(outside_encoded);
+    let distance_to_inside = select(
+        100000.0,
+        distance(pixel_coord, decode_seed(inside_encoded)),
+        has_inside,
+    );
+    let distance_to_outside = select(
+        100000.0,
+        distance(pixel_coord, decode_seed(outside_encoded)),
+        has_outside,
+    );
+    let signed_distance = distance_to_outside - distance_to_inside;
+    let alpha = smoothstep(-uniforms.feather_half, uniforms.feather_half, signed_distance);
+
+    return vec4f(alpha, alpha, alpha, alpha);
+}
-- 
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