Add detail to a large background with smart objects

Last updated: October 11, 2026

Paint more detail into one part of a very large game background, a keep, a hero prop, a focal building, at the resolution it has in the final file, without repainting the whole canvas.

Why this works

A model generates and edits pictures up to a fixed size, a few megapixels. Hand it a whole 8K background and it works on a scaled-down copy, so whatever it adds is soft once the result is stretched back over the full canvas. A smart object turns one part of the background into a document of its own, at that part's own pixel size. Edit that document and the model's whole output resolution goes into the keep alone; save it, and Photoshop writes the new pixels back into the background at full size. The rest of the background is never touched.

What you need

  • Photoshop with the Layer panel installed and signed in (see Layer for Photoshop for the supported versions).
  • A large background with the part you want to detail on a layer of its own, or a selection you can copy to one.
  • The panel's Prompt edit tool. Upscale and Restore work the same way (see Variations).

The workflow

Find the part that falls apart at full size

Zoom the background to 100%, the size a player sees it at. The parts painted at a smaller size, or upscaled from one, look soft next to everything else: that is where the detail goes.

Open that part as a smart object

Put the part on a layer of its own and convert it to a smart object, then open its contents.

  1. Select the layer, right-click it and choose Convert to Smart Object.

  2. Double-click the layer's thumbnail. Photoshop opens its contents in a new tab, a .psb document the size of that part of the background.

Describe the detail in the Layer panel

With the smart object's tab in front, the Layer panel works on that document. Its layer is already selected as the source.

  1. Select Prompt edit.

  2. Describe what the part needs: materials, light sources, the small features that read at full size. Ask it to keep the composition, palette and style as they are.

  3. Select Edit image.

Check the result in the smart object

The edit comes back as a new layer named Prompt edit, above the original, which the panel hides. Compare the two by toggling the original's visibility, and run the tool again if the first take is not right: every take is a layer, so nothing is lost.

Save it back into the background

  1. Press Cmd+S (Windows: Ctrl+S) to save the smart object.

  2. Press Cmd+W (Ctrl+W) to close its tab.

Photoshop updates the smart object in the background. At 100% the part now holds the new detail, and the rest of the canvas is as it was.

Variations

Upscale instead of repaint

When the part only needs to be sharper, not changed, use Upscale inside the smart object instead of Prompt edit. The detail is rebuilt from what is there rather than reinvented.

Restore old or compressed art

For a part that comes from an older, compressed or scanned source, use Restore inside the smart object, then save it back.

Edit only part of the smart object

Make a selection inside the smart object before running Prompt edit. Only the selection changes, and the result comes back as a masked layer.

Production tips

  • Keep the smart object a little larger than the part you are detailing. The model has context at the edges, and you can mask the result back to the part.
  • When the edit shifts the colours, add a layer mask to the result inside the smart object and feather it into the original, so the new detail meets the old paint without a seam.
  • Name each smart object for what it holds (Keep, Bridge, Market stalls): the panel names its session after the open document, so the takes for each part stay together.
  • Work part by part. A background with several smart objects can be detailed in any order, and each one can go back to an earlier take by changing which layer is visible inside it.
  • Before handing the file on, rasterize the smart objects only if the engine import or the next artist needs it; kept as smart objects they stay editable.

If something goes wrong

  • The background did not change after closing the smart object. The contents were closed without saving. Open the smart object again, check the new layer is visible, save with Cmd+S, then close.
  • The panel says it is reading the whole document instead. A group is selected inside the smart object. Select the pixel layer you want to detail.
  • The edit changed more than the part. Describe what to keep as well as what to add, or make a selection inside the smart object so only that area changes.
  • The result looks soft at 100%. The smart object is larger than the model's output size. Split the part into two smart objects, or upscale the result inside the smart object.

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