Add 3D noise(vec3) support to p5.strands

src/webgl/ShaderGenerator.js

@@ -8,6 +8,7 @@ import { parse } from 'acorn';
 import { ancestor } from 'acorn-walk';
 import escodegen from 'escodegen';
 import noiseGLSL from './shaders/functions/noiseGLSL.glsl';
+import noise3DGLSL from './shaders/functions/noise3DGLSL.glsl';
 
 function shadergenerator(p5, fn) {
 
@@ -1663,23 +1664,34 @@ function shadergenerator(p5, fn) {
   const originalNoise = fn.noise;
   fn.noise = function (...args) {
     if (!GLOBAL_SHADER?.isGenerating) {
-      return originalNoise.apply(this, args); // fallback to regular p5.js noise
+      return originalNoise.apply(this, args); // fallback to p5.js noise
     }
-
-    GLOBAL_SHADER.output.vertexDeclarations.add(noiseGLSL);
-    GLOBAL_SHADER.output.fragmentDeclarations.add(noiseGLSL);
-    // Handle noise(x, y) as noise(vec2)
+
     let nodeArgs;
-    if (args.length === 2) {
+
+    if (args.length === 3) {
+    // GLSL vec3 noise(x, y, z)
+      nodeArgs = [fn.vec3(args[0], args[1], args[2])];
+      GLOBAL_SHADER.output.vertexDeclarations.add(noise3DGLSL);
+      GLOBAL_SHADER.output.fragmentDeclarations.add(noise3DGLSL);
+
+      return fnNodeConstructor('noise', nodeArgs, {
+        args: ['vec3'],
+        returnType: 'float',
+      });
+    } else if (args.length === 2) {
+    // GLSL vec2 noise(x, y)
       nodeArgs = [fn.vec2(args[0], args[1])];
-    } else {
-      nodeArgs = args;
+      GLOBAL_SHADER.output.vertexDeclarations.add(noiseGLSL);
+      GLOBAL_SHADER.output.fragmentDeclarations.add(noiseGLSL);
+
+      return fnNodeConstructor('noise', nodeArgs, {
+        args: ['vec2'],
+        returnType: 'float',
+      });
     }
 
-    return fnNodeConstructor('noise', nodeArgs, {
-      args: ['vec2'],
-      returnType: 'float'
-    });
+    return originalNoise.apply(this, args); // fallback again if unexpected
   };
 
 }

src/webgl/shaders/functions/noise3DGLSL.glsl

@@ -0,0 +1,52 @@
+// Based on https://thebookofshaders.com/13/ and https://github.com/patriciogonzalezvivo/lygia
+// MIT licensed, adapted for p5.strands
+
+vec3 random3(vec3 p) {
+  return fract(sin(vec3(
+    dot(p, vec3(127.1, 311.7, 74.7)),
+    dot(p, vec3(269.5, 183.3, 246.1)),
+    dot(p, vec3(113.5, 271.9, 124.6))
+  )) * 43758.5453123);
+}
+
+float baseNoise(vec3 p) {
+  vec3 i = floor(p);
+  vec3 f = fract(p);
+
+  // Compute corner vectors
+  vec3 a = random3(i);
+  vec3 b = random3(i + vec3(1, 0, 0));
+  vec3 c = random3(i + vec3(0, 1, 0));
+  vec3 d = random3(i + vec3(1, 1, 0));
+  vec3 e = random3(i + vec3(0, 0, 1));
+  vec3 f1 = random3(i + vec3(1, 0, 1));
+  vec3 g = random3(i + vec3(0, 1, 1));
+  vec3 h = random3(i + vec3(1, 1, 1));
+
+  vec3 u = f * f * (3.0 - 2.0 * f);
+
+  return mix(
+    mix(
+      mix(dot(a, f - vec3(0, 0, 0)), dot(b, f - vec3(1, 0, 0)), u.x),
+      mix(dot(c, f - vec3(0, 1, 0)), dot(d, f - vec3(1, 1, 0)), u.x), u.y
+    ),
+    mix(
+      mix(dot(e, f - vec3(0, 0, 1)), dot(f1, f - vec3(1, 0, 1)), u.x),
+      mix(dot(g, f - vec3(0, 1, 1)), dot(h, f - vec3(1, 1, 1)), u.x), u.y
+    ),
+    u.z
+  );
+}
+
+float noise(vec3 p) {
+  float result = 0.0;
+  float amplitude = 1.0;
+  float frequency = 1.0;
+
+  for (int i = 0; i < 4; i++) {
+    result += amplitude * baseNoise(p * frequency);
+    frequency *= 2.0;
+    amplitude *= 0.5;
+  }
+  return result;
+}