p5.js performance issues using blendMode()

Hi there!

Inspired by your tutorials on noise I went ahead and made a [simplex noise demo](https://codepen.io/geletina/pen/PoqxNJp). Ideally I would love to also add a multiply blend mode to it but my computer tries to combust when I attempted to add it to `setup()`. Would you happen to have any thoughts on how I might achieve the same effect less intensively and/or make my code more efficient? I was thinking of refactoring to OOP but even then there doesn't seem to be a way to update my geometries without redrawing. Here's [the issue on stackoverflow](https://stackoverflow.com/questions/60921155/blendmode-rendering-issues-p5-js) as well in case you prefer to use that platform.

🙏

Riproduci la demo del rumore simplex nel CodePen collegato con blendMode() abilitato, quindi esamina la discussione collegata su Stack Overflow. L'issue non indica file o test del repository; una risoluzione utile stabilirebbe la causa del rallentamento e documenterebbe un approccio concreto meno dispendioso o una modifica al codice.

Scritto dal modello di indicizzazione a partire dal testo della issue.