How to Clean Up an AI-Generated 3D Model in Blender

AI-generated models get you 80% of the way in a couple of minutes. The last 20% (correct scale, a sensible origin, no floating junk, a reasonable triangle count) is what makes a model behave in a game engine, a render or a slicer. This is the routine we use in Blender 4.x. Every step is quick, and you can skip any that don't apply.

1. Import and look before you touch anything

File → Import → glTF 2.0 (.glb/.gltf). Then orbit around the model in Material Preview mode (Z → Material Preview) and look specifically at:

• the back and underside, which are inferred in image-to-3D and are where problems hide,
• loose bits floating near the model,
• dark patches in the texture that look like painted shadows.

Write down what you see. Fixing blind wastes time.

2. Fix scale and orientation

Generated models have arbitrary units. Press N to open the sidebar and check Dimensions. If a mug is 2 metres tall, scale it down: S, type the factor, Enter. Then apply the transforms with Ctrl+A → All Transforms, so the scale is baked into the mesh and exports cleanly. Check that the model is upright: glTF is Y-up, and Blender's importer converts it to Z-up for you.

3. Put the origin where it belongs

For anything that stands on the ground, the origin should be at the base. Select the model, snap the 3D cursor to the lowest point (or to the world origin if the model already sits on it), then use Object → Set Origin → Origin to 3D Cursor. Engines place objects by their origin, so this saves a lot of fiddling later.

4. Delete floating fragments

Tab into Edit Mode, press P → By Loose Parts, then Tab out. Every disconnected piece is now its own object. Delete the specks you don't want, then select the rest and press Ctrl+J to join them back together. On image-to-3D results there are often a few small fragments from the background.

5. Recalculate normals

In Edit Mode, select all (A) and press Shift+N to recalculate normals outside. Turn on Face Orientation in the Overlays menu: blue is outward, red is inward. Red patches cause black spots in engines and holes in 3D prints.

6. Bring the triangle count down

Add a Decimate modifier (Collapse mode) and lower the ratio while watching the silhouette. For a background prop, 0.2–0.5 is often invisible. Keep an eye on the triangle count in the status bar (enable Scene Statistics if it's hidden). See reducing polygon count for when to retopologise instead.

7. Deal with baked-in lighting

Image-to-3D textures often include the lighting from the original photo. Small amounts are fine. For a strong shadow, open the texture in the Texture Paint workspace and use the Clone or Soften brush. Or, in the material, lower the contrast slightly with a Hue/Saturation/Value node before the Base Color input. The real fix is a better source photo: evenly lit, no hard shadows.

8. Prepare for printing (if you're printing)

Install the 3D-Print Toolbox (a bundled add-on in older Blender versions, a free extension from Edit → Preferences → Get Extensions in 4.2 and later) and run Check All. It reports non-manifold edges, thin walls and intersections. For stubborn models, a Remesh modifier in Voxel mode rebuilds a watertight surface. Set the voxel size small enough to keep the detail you care about.

9. Export

Going to…	Export as	Key settings
Web, Godot, three.js	glTF Binary (.glb)	Apply Modifiers on; enable Draco compression if your viewer supports it
Unity, Unreal	FBX	Apply Scalings: FBX All; Forward: -Z; Up: Y
Slicer	STL or 3MF	Apply Modifiers on; Scene Unit checked

A ten-minute habit

Run these steps once and they become a quick routine. Most models only need steps 1–5 and 9. Start with a model from our image to 3D converter, or practise on any model in the free library.