Auto cleanup and Tidy geometry

Two cards in the right sidebar, under Clean up, hold one-click commands. Each is one undo step.

Auto cleanup

Remove empty parts

Deletes parts that contain no triangles. Files often carry a few of these.

Fix degenerate parts

Removes parts whose triangles have no area, which can confuse the programs that draw them.

Delete empty groups

Removes groups that have no parts left in them.

Deduplicate geometry

Looks for parts whose mesh data is identical to another part’s. See the note below before you use it.

Each command reports what it did, or says that it found nothing.

Tidy geometry

Recompute smooth normals

Works out the shading directions of every surface again. Use it when parts look oddly faceted or dark after large changes.

Recentre on origin

Moves the model so the centre of its bounding box sits at 0,0,0.

Bake gizmo transforms

Makes the moves, turns and scalings you did with the gizmo permanent in the mesh itself.

Centre pivot

Moves the pivot of each selected part to the centre of its bounding box. The part does not move on screen.

Flags

The card Filters & flags, under Inspect, marks suspicious parts without changing them:

Flag low-triangle parts

Marks parts with fewer triangles than the slider says.

Flag thin slivers

Marks parts that are extremely long for their width, such as gaskets, wires and decals.

The status bar shows how many parts are flagged. Click that number to isolate them, look at them, and decide what to do.