feature: improve snowflake rendererHEADmaster

2 files changed, 103 insertions, 0 deletions

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;
+}
diff --git a/themes/src/_shaders/snowflake.vert b/themes/src/_shaders/snowflake.vert
new file mode 100644
index 0000000..7cbfb99
--- /dev/null
+++ b/themes/src/_shaders/snowflake.vert
@@ -0,0 +1,30 @@
+// Instanced snowflake vertex shader
+attribute vec2 position;        // Base quad vertex position
+attribute vec2 instancePos;     // Per-instance: snowflake center position
+attribute float instanceRot;    // Per-instance: rotation angle
+attribute float instanceScale;  // Per-instance: size scale
+attribute float instanceSeed;   // Per-instance: random seed for variation
+
+uniform mat4 projection;
+uniform mat4 model;
+
+varying lowp vec2 vUV;           // UV coordinates for fragment shader
+varying lowp float vSeed;        // Pass seed to fragment shader
+varying lowp float vScale;       // Pass scale to fragment shader
+
+void main() {
+    // Rotate and scale the base quad
+    float c = cos(instanceRot);
+    float s = sin(instanceRot);
+    mat2 rotation = mat2(c, s, -s, c);
+
+    vec2 rotatedPos = rotation * (position * instanceScale);
+    vec2 worldPos = instancePos + rotatedPos;
+
+    gl_Position = projection * model * vec4(worldPos, 0.0, 1.0);
+
+    // Pass UV in range [-1, 1] for procedural generation
+    vUV = position;
+    vSeed = instanceSeed;
+    vScale = instanceScale;
+}