Scratches Generator

Scratches are the fastest way to make a material stop looking like plastic, but generating them with a diffusion model is overkill and a lot of VRAM. Scratches Generator just draws them. It's a pure procedural node: give it a canvas size, a density, and a seed, and it paints a field of scratch lines on a black background. No model, no weights, no sampling - it's the kind of utility you reach for when you want a wear plate to multiply into a roughness or metallic map.

How it works

The generator picks a random start point for each scratch, a random length between length_min and length_max, and a random angle. angle_variation controls the angular spread - 0 makes every scratch vertical, 180 means all directions. Each line is rasterized with a soft-edged falloff at intensity brightness and a pixel width set by width_scratch. The number of scratches is width × height × density / 10000, so it scales with pixel area - quadruple the pixels and you get four times the scratches.

It outputs two things:

• scratches - white lines on black, ready to multiply into roughness or use as a wear mask.
• height - the same scratches as a height field (1 - scratches * 0.3), so grooves read as darker indentations. Wire it into a height input or a height-to-normal converter if you want actual geometry.

The seed input makes the pattern reproducible, which matters when you're iterating on a material set and want the same scratches on the albedo and the roughness map.

What to set first

Density is the one that shapes the result most - 0.3 is a light scuff, 0.8 is a heavily beat-up surface. intensity is brightness, not opacity of the effect; 0.8 reads as proper bright scratches, and dropping it to ~0.3 gives faint micro-scratches that sit nicely under a roughness detail pass. Keep width_scratch near 1 for believable hairline marks.

Installing and running it

It's part of the amtarr/ComfyUI-TextureAlchemy pack. Install via ComfyUI Manager (search "Texture Alchemy") or:

cd ComfyUI/custom_nodes
git clone https://github.com/amtarr/ComfyUI-TextureAlchemy

Then restart and find it under right-click → Add Node → Texture Alchemist → Procedural. The pack has no extra dependencies and no model files - everything runs on the PyTorch/PIL/NumPy that ComfyUI ships.

The honest gotchas

This one is CPU-bound in a way that hurts. Each line is drawn in a Python loop with a hand-rolled line rasterizer, and the scratch count scales with pixel area. At 2048×2048 with high density it turns into a wait, and 8192 (the max) with density near 1.0 is genuinely slow. Build and preview at 512 or 1024, then bump up for the final pass. Also worth knowing: the pack prints a banner to the console on every run - normal behavior, not an error. If your scratches come out looking like a scribble pad, lower density and raise length_min; dense short scratches read as noise, sparse long ones read as wear.