Great question @Lu_Bacc — and you’re definitely not alone! The documentation on Physical Material Masks is pretty sparse, and the “8-color map” explanation often gets glossed over. Let’s break it down 
What is an 8-color Mask Map?
A Physical Material Mask in Unreal lets you define up to 8 different physical materials on a single mesh, based on a mask texture.
Each of those 8 physical materials corresponds to one of these 8 basic colors in the mask:
- Red (255,0,0)
- Green (0,255,0)
- Blue (0,0,255)
- Cyan (0,255,255)
- Magenta (255,0,255)
- Yellow (255,255,0)
- White (255,255,255)
- Black (0,0,0)
You don’t need 8 layers in Photoshop — just one image where each region is filled with one of those colors.
How to Make One in Photoshop:
- Create a new 8-bit RGB image.
- Paint the areas of your mesh you want to assign to each physical material using the solid colors listed above.
- Avoid blending or anti-aliasing — this mask needs to be sharp and uncompressed.
- Export as PNG or TGA (lossless).
Tip: Make sure compression settings in Unreal are set to Vector Displacementmap or Masks, so you don’t get smoothing/artifacts.
If You Want to Go Beyond Photoshop:
- Blender lets you bake masks using vertex colors or UV islands → export to texture
- Substance Painter is another great way to paint ID maps directly onto complex models
Bonus: Keeping Track of Which Color = Which Material
Once you’re using physical masks across multiple assets, it’s easy to forget what red vs. cyan meant, or which model has which assignments.
That’s why we built Asset Optics — a plugin that lets you:
Comment directly on meshes like “Red = grass, Blue = mud”- Track checklist steps like “mask baked,” “physical materials assigned,” etc.
Sync all notes to a web dashboard so your team (or future you) knows what’s been done
Super handy when dealing with material libraries, layered FX, or shared assets across levels.
Let us know how it goes — happy to drop a sample .PSD if you want something to test with!