What merging masks means in Substance Painter

Merging masks in Substance Painter means combining two or more separate mask layers into a single layer. When you merge masks, Substance Painter flattens them together — the result is one mask that contains all the information from the masks you combined. This is different from deleting masks: merging keeps all the detail, just in a consolidated form.

You merge masks when you have finished layering and refining them, and you want to simplify your layer stack or prepare your work for export. Once masks are merged, you cannot separate them again, so this is a one-way operation. Most painters merge masks near the end of a project, after all the detail work is done.

Key Takeaways

  • Merging masks combines multiple mask layers into one, keeping all the visual information but removing the separate layer structure.
  • You can merge two masks at a time by right-clicking one mask and selecting "Merge Down", or merge all masks in a stack using the Layer menu.
  • Merging is permanent — once combined, you cannot undo the merge by separating the layers again, so save a backup version first.
  • Merged masks take up less file space and simplify your layer panel, but you lose the ability to edit individual masks separately.

How to merge two masks at once

The fastest way to merge two masks is to use the "Merge Down" command. Click on the upper mask in your layer stack — the one you want to merge into the mask below it. Right-click on that mask and select "Merge Down" from the context menu. Substance Painter will combine the selected mask with the mask directly beneath it.

The merged result stays in the position of the lower mask. The upper mask disappears from your layer panel. If you had any blend modes or opacity settings on the upper mask, those effects are baked into the merged result.

How to merge all masks in a stack

If you have three or more masks and want to combine them all at once, use the Layer menu instead. Click Layer in the top menu bar, then look for Merge Down or Flatten depending on your Substance Painter version. "Flatten" will merge all visible layers in the entire stack into a single layer.

Before you flatten, make sure every mask you want to keep is set to visible — click the eye icon next to each mask so you can see it. Any mask with the eye icon hidden will not be included in the merge. After you flatten, all masks become one, and your layer panel will show only that single merged mask.

What happens to blend modes and opacity when you merge

When you merge masks, Substance Painter applies the blend mode and opacity of the upper mask to the pixels it contains, then combines the result with the lower mask. This means the visual effect you see on screen becomes permanent in the merged mask — you cannot adjust the blend mode or opacity of that part afterward without editing the mask itself.

If you want to preserve the ability to change blend modes or opacity later, do not merge. Instead, keep the masks separate and export your texture map with all layers intact. If you do merge, the blended appearance is locked in.

When to merge masks and when to keep them separate

Merge masks when you have finished all your detail work and are ready to finalize the texture. Merging reduces file size, makes the layer panel easier to read, and speeds up your computer if you are working with many layers. It also simplifies export — a single merged mask is straightforward to save as a texture file.

Keep masks separate if you think you might need to adjust them later, or if you are still experimenting with blend modes and opacity. Separate masks give you flexibility. If your project file is already large or your computer is slow, merging earlier can help performance, but you trade that speed for the ability to edit individual masks.

How to save before you merge

Always save a copy of your project file before merging masks. Use File > Save As and give the file a new name — for example, "texture_final_merged" instead of "texture_working". Keep the original file with all the separate masks in case you need to go back and adjust something.

Substance Painter project files are saved as .spp files. These files store all your layers and masks in editable form. When you export your texture for use in a game engine or 3D software, you export as .png, .tga, or another image format — that export is separate from your project file and does not affect your ability to edit the masks later in the .spp file.

Frequently Asked Questions

Can I undo a merge after I have done it?

Yes, if you have not closed the file. Use Edit > Undo or press Ctrl+Z (Windows) or Command+Z (Mac) to step back through your recent actions. If you have closed and reopened the file, the undo history is gone and you cannot recover the separate masks — this is why saving a backup before you merge is important.

What is the difference between merging and flattening?

Merging combines two adjacent layers. Flattening combines all visible layers at once into a single layer. Use merge when you want to combine just a couple of masks; use flatten when you want to collapse your entire layer stack into one.

Do I need to merge masks before I export my texture?

No. You can export with all your masks separate — Substance Painter will flatten them automatically during export. Merging in your project file is optional and is mainly for organization and file size. Export settings control what gets saved to your final texture file.

Will merging masks change how my texture looks?

Only if the upper mask has a blend mode other than "Normal" or an opacity setting below 100 percent. In those cases, the blended appearance becomes permanent. If both masks are set to Normal blend mode and 100 percent opacity, merging will not change the visual result.

Can I merge a mask with a layer that is not a mask?

In Substance Painter, masks and paint layers are different things. You can merge masks with masks, and you can merge paint layers with paint layers, but the process is the same — right-click and select "Merge Down". The result depends on what you are merging: two masks become one mask, two paint layers become one paint layer.