From fbc5d7dd1a9192c29daccdf12a7a067037ff2c2a Mon Sep 17 00:00:00 2001
From: Matt Kosarek <matt.kosarek@canonical.com>
Date: Mon, 29 Dec 2025 10:02:38 -0500
Subject: Improve the sun shader with the help of AI

---
 themes/src/_shaders/sun.frag | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

(limited to 'themes/src/_shaders/sun.frag')

diff --git a/themes/src/_shaders/sun.frag b/themes/src/_shaders/sun.frag
index 8463e06..028c0c2 100644
--- a/themes/src/_shaders/sun.frag
+++ b/themes/src/_shaders/sun.frag
@@ -1,5 +1,43 @@
 varying lowp vec4 VertexColor;
+varying lowp vec2 TexCoord;
+uniform lowp float time;
+
+// Simple noise function for edge distortion
+lowp float noise(lowp vec2 p) {
+    return sin(p.x * 10.0 + time) * cos(p.y * 10.0 + time * 0.5) * 0.5 + 0.5;
+}
 
 void main() {
-    gl_FragColor = VertexColor;
+    // TexCoord is now normalized: center is (0,0), edges are at distance ~1
+    lowp float dist = length(TexCoord);
+
+    // Add animated noise to the edge
+    lowp float angle = atan(TexCoord.y, TexCoord.x);
+    lowp float wave = sin(angle * 8.0 + time * 2.0) * 0.05 + sin(angle * 4.0 - time * 1.5) * 0.03;
+    lowp float noiseValue = noise(TexCoord + time * 0.1) * 0.02;
+
+    // Create soft edge using smoothstep - ensure fade reaches zero at the actual edge
+    lowp float innerEdge = 0.2;
+    lowp float outerEdge = 1.0;
+    lowp float alpha = 1.0 - smoothstep(innerEdge, outerEdge, dist);
+
+    // Apply wave distortion to the edge
+    alpha *= 1.0 - smoothstep(0.85 + wave + noiseValue * 2.0, 1.0, dist);
+
+    // Make edges even more transparent with additional fade
+    alpha = alpha * alpha * alpha;
+
+    // Add slight glow effect at the edge
+    lowp float glow = smoothstep(0.5, 0.8, dist) * (1.0 - smoothstep(0.8, 1.0, dist));
+
+    // Create orange gradient from center
+    lowp vec3 orangeColor = vec3(1.0, 0.5, 0.1);
+    lowp float centerGradient = smoothstep(0.6, 0.0, dist);
+    lowp vec3 baseColor = mix(VertexColor.rgb, orangeColor, centerGradient * 0.6);
+
+    // Mix in the glow with a brighter color
+    lowp vec3 glowColor = baseColor * 1.3;
+    lowp vec3 finalColor = mix(baseColor, glowColor, glow * 0.5);
+
+    gl_FragColor = vec4(finalColor, VertexColor.a * alpha);
 }
-- 
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