I did this a while back, but someone had an interest in this on hackaday so I tried to dig up my old code.
The goal is to generate wood grain patterns for laser cutting/CNC of plywood. Mainly, I wanted to have something similar to spalted maple laser etched onto the plain birch veneered plywood. The thing that inspired this project was this post of speaker boxes on imgur I came across. The design looked really cool, and while spalted maple is expensive, birch plywood is relatively cheap.
My first step was to procedurally create a random pattern. Similar to the imgur post, I looked at creating camouflage. I found a great example code on openprocessing by ThingOnItsOwn that used perlin noise to create a camouflage pattern. I tweaked the values a bit experimentally, then stretched the entire design to make the final design look more like woodgrain.
The next step was to just capture the edges of these blob shapes from the first pattern. I came across this example from Richard Bourne It is forked from this example from R. Luke DuBois. Honestly I was being lazy because I had written edge detection code in college as it is standard image processing, but I knew someone else had it already in processing. Instead of using for loops, this version manually calculates out the kernel.
This leaves me with a result that looks pretty realistic.
Camo:
Spalting:
This creates a PNG filetype which can be used to add texture to a 3D print in the slicer. The slicer will adjust the print to incorporate the texture in 3D giving it a woodgrain-like effect. You technically could use this as-is on a laser cutter to create spalting like my inspiration, however being raster data, it would take the laser a long time. It’d have to scan the laser (the thickness of a human hair) across the entire area of the panel you are applying the texture on. To make this faster, you can vectorize the PNG in inkscape or other software to outline the dark areas of the PNG. This will cut fast as it is a vector (the laser would just have to draw the lines the same way your hand would. That would save a lot of time.
If anyone wants to add vectorizing to my code, please do! You can clone my github and put it on P5.js. I was going to add it, but I got lazy again. I even asked ChatGPT3 to help combine this code with something like potrace or imagetracerjs but it produced code that looked great, some even compiled after a few tweaks, but never worked.