Add noiseDetail() support for p5.strands

src/math/noise.js

@@ -397,6 +397,22 @@ function noise(p5, fn){
     }
   };
 
+  /**
+   * @private
+   * Returns the current number of octaves used by noise().
+   */
+  fn._getNoiseOctaves = function() {
+    return perlin_octaves;
+  };
+
+  /**
+   * @private
+   * Returns the current falloff factor used by noise().
+   */
+  fn._getNoiseAmpFalloff = function() {
+    return perlin_amp_falloff;
+  };
+
   /**
    * Sets the seed value for the <a href="#/p5/noise">noise()</a> function.
    *

src/strands/strands_api.js

@@ -104,6 +104,20 @@ export function initGlobalStrandsAPI(p5, fn, strandsContext) {
   }
   // Add GLSL noise. TODO: Replace this with a backend-agnostic implementation
   const originalNoise = fn.noise;
+  const originalNoiseDetail = fn.noiseDetail;
+
+  strandsContext._noiseOctaves = null;
+  strandsContext._noiseAmpFalloff = null;
+
+  fn.noiseDetail = function (lod, falloff) {
+    if (!strandsContext.active) {
+      return originalNoiseDetail.apply(this, arguments);
+    }
+
+    strandsContext._noiseOctaves = lod;
+    strandsContext._noiseAmpFalloff = falloff;
+  };
+
   fn.noise = function (...args) {
     if (!strandsContext.active) {
       return originalNoise.apply(this, args); // fallback to regular p5.js noise
@@ -131,9 +145,20 @@ export function initGlobalStrandsAPI(p5, fn, strandsContext) {
         `It looks like you've called noise() with ${args.length} arguments. It only supports 1D to 3D input.`
       );
     }
+
+    const octaves = strandsContext._noiseOctaves !== null
+      ? strandsContext._noiseOctaves
+      : fn._getNoiseOctaves();
+    const falloff = strandsContext._noiseAmpFalloff !== null
+      ? strandsContext._noiseAmpFalloff
+      : fn._getNoiseAmpFalloff();
+
+    nodeArgs.push(octaves);
+    nodeArgs.push(falloff);
+
     const { id, dimension } = build.functionCallNode(strandsContext, 'noise', nodeArgs, {
       overloads: [{
-        params: [DataType.float3],
+        params: [DataType.float3, DataType.int1, DataType.float1],
         returnType: DataType.float1,
       }]
     });

src/webgl/shaders/functions/noise3DGLSL.glsl

@@ -93,15 +93,16 @@ float baseNoise(vec3 v)
         dot(p2,x2), dot(p3,x3) ) );
 }
 
-float noise(vec3 st) {
+float noise(vec3 st, int octaves, float ampFalloff) {
   float result = 0.0;
   float amplitude = 1.0;
   float frequency = 1.0;
 
-  for (int i = 0; i < 4; i++) {
+  for (int i = 0; i < 8; i++) {
+    if (i >= octaves) break;
     result += amplitude * baseNoise(st * frequency);
     frequency *= 2.0;
-    amplitude *= 0.5;
+    amplitude *= ampFalloff;
   }
 
   return result;