Add noiseGLSL.glsl with MIT-licensed 2D noise for p5.strands

Author: LalitNarayanYadav

src/webgl/shaders/functions/noiseGLSL.glsl

@@ -1,13 +1,29 @@
-float baseNoise(vec2 st) {
-  return fract(sin(dot(st.xy ,vec2(12.9898,78.233))) * 43758.5453123);
+// Based on https://github.com/patriciogonzalezvivo/lygia/blob/main/generative/noise.glsl (MIT)
+// Adapted for use in p5.strands
+
+vec2 random2(vec2 st) {
+  st = vec2(dot(st, vec2(127.1, 311.7)),
+            dot(st, vec2(269.5, 183.3)));
+  return -1.0 + 2.0 * fract(sin(st) * 43758.5453123);
 }
 
-float noise(vec2 st) {
-  float result = 0.0;
-  for (int i = 0; i < 3; i++) {
-    float freq = pow(2.0, float(i));
-    float amp = pow(0.5, float(i));
-    result += amp * baseNoise(st * freq);
-  }
-  return result;
+float baseNoise(vec2 st) {
+  vec2 i = floor(st);
+  vec2 f = fract(st);
+
+  // Four corners in 2D of a tile
+  vec2 a = random2(i);
+  vec2 b = random2(i + vec2(1.0, 0.0));
+  vec2 c = random2(i + vec2(0.0, 1.0));
+  vec2 d = random2(i + vec2(1.0, 1.0));
+
+  // Smooth interpolation
+  vec2 u = f * f * (3.0 - 2.0 * f);
+
+  // Mix the results
+  return mix(mix(dot(a, f - vec2(0.0, 0.0)), 
+                 dot(b, f - vec2(1.0, 0.0)), u.x),
+             mix(dot(c, f - vec2(0.0, 1.0)), 
+                 dot(d, f - vec2(1.0, 1.0)), u.x), u.y);
 }
+