Add custom fn.noise() in p5.strands with conditional GLSL injection

Author: LalitNarayanYadav

src/webgl/ShaderGenerator.js

@@ -1631,11 +1631,19 @@ function shadergenerator(p5, fn) {
       return originalLerp.apply(this, args); // Fallback to normal p5.js lerp
     }
   };
+  fn.noise = function (...args) {
+    if (GLOBAL_SHADER?.isGenerating) {
+      GLOBAL_SHADER.output.fragmentDeclarations.add(noiseGLSL);
+      return fnNodeConstructor('noise', args, { args: ['vec2'], returnType: 'float' });
+    } else {
+      p5._friendlyError(
+        `It looks like you've called noise() outside of a shader's modify() function.`
+      );
+    }
+  };
 }
 
 
-GLOBAL_SHADER.output.fragmentDeclarations.add(noiseGLSL);
-
 export default shadergenerator;
 
 if (typeof p5 !== 'undefined') {