From b4e8ae9731eca175cd4e6e75a20da87ff86eb91f Mon Sep 17 00:00:00 2001
From: Matt Kosarek <matt.kosarek@canonical.com>
Date: Tue, 3 Feb 2026 08:13:30 -0500
Subject: feature: improve snowflake renderer

---
 themes/src/_shaders/snowflake.frag | 73 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 themes/src/_shaders/snowflake.frag

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

diff --git a/themes/src/_shaders/snowflake.frag b/themes/src/_shaders/snowflake.frag
new file mode 100644
index 0000000..d887cf5
--- /dev/null
+++ b/themes/src/_shaders/snowflake.frag
@@ -0,0 +1,73 @@
+// Procedural star fragment shader
+varying lowp vec2 vUV;
+varying lowp float vSeed;
+varying lowp float vScale;
+
+const lowp float PI = 3.14159265359;
+
+// Simple hash function for deterministic randomness
+lowp float hash(lowp float n) {
+    return fract(sin(n) * 43758.5453123);
+}
+
+// Generate star pattern procedurally
+lowp float starPattern(lowp vec2 uv) {
+    lowp float dist = length(uv);
+    lowp float angle = atan(uv.y, uv.x);
+
+    // Number of star points (4 or 5)
+    lowp float numPoints = 4.0 + floor(hash(vSeed) * 2.0);
+
+    // Create sharp star with triangular points
+    lowp float angleStep = 2.0 * PI / numPoints;
+    lowp float currentAngle = mod(angle + PI / numPoints, angleStep) - angleStep * 0.5;
+
+    // Create triangular points - distance from center to edge varies linearly with angle
+    lowp float normalizedAngle = abs(currentAngle) / (angleStep * 0.5);
+
+    // Outer tip radius and inner valley radius
+    lowp float tipRadius = 0.5;
+    lowp float valleyRadius = 0.15;
+
+    // Linear interpolation creates sharp triangular points
+    lowp float rayEdge = mix(tipRadius, valleyRadius, normalizedAngle);
+
+    // Hard cutoff for sharp edges
+    lowp float star = step(dist, rayEdge);
+
+    return star;
+}
+
+void main() {
+    lowp float pattern = starPattern(vUV);
+
+    // Color variation based on seed - white and blue tints
+    lowp float colorVar = hash(vSeed * 3.0);
+    lowp vec3 starColor;
+
+    if (colorVar < 0.5) {
+        // Pure white
+        starColor = vec3(1.0, 1.0, 1.0);
+    } else if (colorVar < 0.75) {
+        // Light blue tint
+        starColor = vec3(0.9, 0.95, 1.0);
+    } else {
+        // Stronger blue tint
+        starColor = vec3(0.85, 0.92, 1.0);
+    }
+
+    // Scale alpha based on size - smaller stars are more transparent
+    // Normalize scale from range [16, 48] to [0, 1]
+    lowp float sizeRatio = (vScale - 16.0) / (48.0 - 16.0);
+    // Map to alpha range [0.3, 1.0] - smaller stars at 30% opacity, larger at 100%
+    lowp float alpha = mix(0.3, 1.0, sizeRatio);
+
+    lowp vec4 color = vec4(starColor, pattern * alpha);
+
+    // Discard fully transparent pixels for performance
+    if (color.a < 0.01) {
+        discard;
+    }
+
+    gl_FragColor = color;
+}
-- 
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