CC Bubbles: bubbles at the layer's edges refract its edge pixels, not a pale fill (#2024)

Near the borders a bubble's refraction (liquid) or reflection (metal) sample
lands outside the layer. sample_bilinear returns transparent there, so the
pale stand-in colour for transparent pixels showed through, a band of washed-out
bubbles along every edge. Sample with edge pixels repeated instead, on the CPU
and in the GPU kernel; the pale colour stays for genuinely transparent pixels.

The CC Bubbles golden hashes are re-pinned (the half-resolution cases pad the
buffer with transparent pixels and are unchanged).

crates/effects/src/sim/tests.rs

@@ -97,6 +97,21 @@ fn bubbles_rise() {
     assert!(y0 >= 0.0 && y1 >= 0.0 && (y1 < y0 || y0 < 8.0), "{y0} -> {y1}");
 }
 
+/// #2024: bubbles near the layer's edges show its edge pixels, not the pale colour that stands
+/// in for transparent ones.
+#[test]
+fn bubbles_near_edges_show_the_layer() {
+    let blue = Image::filled(40, 40, [0.0, 0.0, 1.0, 1.0]);
+    let pale = [0, 1].map(|reflection| {
+        let vals = [("bubbleAmount", num(200.0)), ("bubbleSize", num(3.0)), ("reflectionType", Value::Enum(reflection))];
+        let a = run("ec.sim.ccbubbles", &vals, blue.clone(), 0.3);
+        assert!(a.data.iter().any(|p| p[3] > 0.5), "bubbles drawn");
+        // Blue plus the white highlight keeps blue − red = alpha; the pale colour leaves 0.2 · alpha.
+        a.data.iter().filter(|p| (p[2] - p[0] - p[3]).abs() > 1e-4).count()
+    });
+    assert_eq!(pale, [0, 0], "pale bubble pixels (liquid, metal)");
+}
+
 #[test]
 fn drizzle_ripples() {
     let a = run("ec.sim.ccdrizzle", &[], ramp(48, 48), 0.6);

crates/effects/src/sim/weather.rs

@@ -182,7 +182,7 @@ pub(super) fn bubbles(ctx: &EffectCtx, mut b: Buf) -> Buf {
             // Liquid refracts (inverted, magnified), metal reflects (wide-angle mirror).
             let k = if metal { 1.6 } else { -0.7 };
             let nz = (1.0 - d2).max(0.0).sqrt();
-            let p = src.sample_bilinear((q.sx + dx * q.r * k) as f64, (q.sy + dy * q.r * k) as f64);
+            let p = src.sample_bilinear_clamped((q.sx + dx * q.r * k) as f64, (q.sy + dy * q.r * k) as f64);
             let (c, sa) = unpremul(p);
             let mut c = if sa <= 0.0 { [0.6, 0.7, 0.8] } else { c };
             let mut a = cov;

crates/effects/tests/it/sim_golden.rs

@@ -433,26 +433,26 @@ const GOLDEN: &[(&str, u64)] = &[
     ("ec.sim.ccstarburst/1/32bpc/t1.5", 0x5c39f8b1bd0e9e43),
     ("ec.sim.ccstarburst/1/32bpc/t0.8", 0xdf20aa9dcf4b3e22),
     ("ec.sim.ccstarburst/1/32bpc/t2.2", 0x4fa441737bfcb64d),
-    ("ec.sim.ccbubbles/0/8bpc/t0.5", 0xdcd187e75eeb2fae),
-    ("ec.sim.ccbubbles/0/8bpc/t1.5", 0x835ca088747736ed),
-    ("ec.sim.ccbubbles/0/8bpc/t0.8", 0x5cbb1a6fbb77b41d),
-    ("ec.sim.ccbubbles/0/8bpc/t2.2", 0x3b168068f5bfa533),
-    ("ec.sim.ccbubbles/0/32bpc/t0.5", 0x524b84d14edd77e2),
-    ("ec.sim.ccbubbles/0/32bpc/t1.5", 0xfd7a17f0d40f2a27),
-    ("ec.sim.ccbubbles/0/32bpc/t0.8", 0x70dd2b2b4ff0f7ce),
-    ("ec.sim.ccbubbles/0/32bpc/t2.2", 0xae21dd5cc2c2c07c),
+    ("ec.sim.ccbubbles/0/8bpc/t0.5", 0x6cb63df0c062fdf4),
+    ("ec.sim.ccbubbles/0/8bpc/t1.5", 0x5bb1350114234ac3),
+    ("ec.sim.ccbubbles/0/8bpc/t0.8", 0xaa824d49f12c4156),
+    ("ec.sim.ccbubbles/0/8bpc/t2.2", 0x3528577358c4fc90),
+    ("ec.sim.ccbubbles/0/32bpc/t0.5", 0xdcd8e71222c13a9a),
+    ("ec.sim.ccbubbles/0/32bpc/t1.5", 0xd09565e124d8f5db),
+    ("ec.sim.ccbubbles/0/32bpc/t0.8", 0x91242f8e1fd0ad84),
+    ("ec.sim.ccbubbles/0/32bpc/t2.2", 0x1f9782131e62149d),
     ("ec.sim.ccbubbles/0/8bpc/half/t0.5", 0x931b4ca707604220),
     ("ec.sim.ccbubbles/0/8bpc/half/t1.5", 0x21c25d4555abebe9),
     ("ec.sim.ccbubbles/0/8bpc/half/t0.8", 0x7e05972683359632),
     ("ec.sim.ccbubbles/0/8bpc/half/t2.2", 0xadc4f7219dab4921),
-    ("ec.sim.ccbubbles/1/8bpc/t0.5", 0x89d27a2fe2011067),
-    ("ec.sim.ccbubbles/1/8bpc/t1.5", 0x2bbfee897bf5bf6e),
-    ("ec.sim.ccbubbles/1/8bpc/t0.8", 0x26cc704e7b06fffc),
-    ("ec.sim.ccbubbles/1/8bpc/t2.2", 0x959d331545d96479),
-    ("ec.sim.ccbubbles/1/32bpc/t0.5", 0xaf486cebfcbf4641),
-    ("ec.sim.ccbubbles/1/32bpc/t1.5", 0xe150e9fdb558036f),
-    ("ec.sim.ccbubbles/1/32bpc/t0.8", 0x6395f3967cb24284),
-    ("ec.sim.ccbubbles/1/32bpc/t2.2", 0x68a55894d86ffb9e),
+    ("ec.sim.ccbubbles/1/8bpc/t0.5", 0x2f5415c679ff0980),
+    ("ec.sim.ccbubbles/1/8bpc/t1.5", 0xfcfc354dcd22e6d0),
+    ("ec.sim.ccbubbles/1/8bpc/t0.8", 0xdf90fd57c217019c),
+    ("ec.sim.ccbubbles/1/8bpc/t2.2", 0xd365c88c12219802),
+    ("ec.sim.ccbubbles/1/32bpc/t0.5", 0x50f20497f40bb46d),
+    ("ec.sim.ccbubbles/1/32bpc/t1.5", 0x74760599ffba220a),
+    ("ec.sim.ccbubbles/1/32bpc/t0.8", 0x028de52900ed8618),
+    ("ec.sim.ccbubbles/1/32bpc/t2.2", 0xaf0e21d9a7f625fe),
     ("ec.sim.ccdrizzle/0/8bpc/t0.5", 0x2bdfbc17d92b65b5),
     ("ec.sim.ccdrizzle/0/8bpc/t1.5", 0x8c354c46f99e35d3),
     ("ec.sim.ccdrizzle/0/8bpc/t0.8", 0x891f331ba47ee557),

crates/gpu/src/shaders/fx_sim.wgsl

@@ -180,7 +180,7 @@ fn fxm_bubble(at: u32, x: f32, y: f32) -> FxmShade {
     }
     let k = select(-0.7, 1.6, P.u[1].y != 0u);
     let nz = sqrt(max(1.0 - d2, 0.0));
-    let s = fxm_unpremul(sample_bilinear(src, data[at + 4u] + dx * qr * k, data[at + 5u] + dy * qr * k));
+    let s = fxm_unpremul(sample_bilinear_clamped(src, data[at + 4u] + dx * qr * k, data[at + 5u] + dy * qr * k));
     var c = s.xyz;
     if (s.w <= 0.0) {
         c = vec3<f32>(0.6, 0.7, 0.8);