kirra-docs

Clean Mesh

Finds and repairs the faults that stop a surface working as a solid — open edges, crossing and overlapping triangles, unwelded points and mixed-up normals. Use it before a volume, a boolean, a clip or a slice, and whenever a surface imported from another package behaves oddly.

Clean Mesh dialog on an open surface — the Open Edges row shows 45

Check and repair a surface

Click Clean Mesh on the Surface toolbar. The Clean Mesh dialog opens on the first visible surface, switches the view to 3D, and runs a check.
Choose the surface from the list, or click the target button and click it in the 3D view.
Tick the faults you want to look for under Diagnostics, then click Check. Each row shows a count, and the faults are highlighted in 3D.
Click the button on a row to repair that fault. Kirra re-checks afterwards.
Click Close when the counts are where you want them.

Repairs change the surface in place and are saved straight away. Each repair is one step you can undo with Ctrl+Z and redo with Ctrl+Y. On a surface of more than 500,000 triangles a repair cannot be undone — the status bar says so — so keep a copy or export it first.

Tip: When the surface is not closed, an orange banner reads “Priority: Close the solid to achieve a valid volume”. Deal with Open Edges first: several remove buttons stay disabled until it is fixed, with the tip “Fix open edges first. Removing triangles may break topology.”

Diagnostics

Row	On by default	Repair	What it finds
Open Edges	Yes	Fill, Close	Edges used by only one triangle — gaps and holes
Non-Manifold	No	Remove	Edges shared by more than two triangles
Co-linear XY Triangles	No	Remove	Triangles with no area in plan (vertical slivers)
Zero Area Degenerate	No	Remove	Triangles with no area at all
Crossing Tris	No	Remove	Triangles that pass through each other
Coincident Overlaps	No	Resolve	Triangles lying on top of each other
T-Junctions	No	Resolve	A point sitting on another triangle’s edge without joining it
XY Overlapping Tris	No	Remove	Triangles overlapping in plan
Unwelded Verts	Yes	Weld	Points that should be one point

Tolerance: sets the weld distance — default 0.0012 m. It is remembered in this browser and used only by Clean Mesh.

Open the arrow on a row to list each fault. Click an item to zoom to it; its own repair button fixes only that one, after showing a before-and-after with Apply or Cancel.

Fill or Close?

Fill patches holes whose edges form a clean loop, and keeps the result only if the open edges went down. If it cannot, it suggests a Weld at about 0.001–0.002 m first.
Close works harder: it welds, removes bad triangles, stitches nearby edges and caps what is left. Use it when Fill says “Fill couldn’t close these”.

Some repairs check first and warn when they would open the mesh or remove a lot — Continue or Cancel.

Tools and normals

Control	What it does
Edit Mesh	Opens the Mesh Edit tool to fix triangles by hand
Resolve Winding	Re-cuts triangles that fold through each other
Show Normals	Draws the direction each triangle faces
In / Out	Points every normal into or out of a closed solid
Flip	Reverses every triangle of an open surface
Align	Makes the triangles of an open surface face the same way
Orient	Fixes winding across the whole mesh and reports the volume

In and Out appear only for closed solids; Flip and Align only for open surfaces.

Stats at the foot of the dialog lists points, edges and faces, whether the surface is Closed, the open edges and the volume. A volume is only reliable when Closed reads Yes.

Troubleshooting

Symptom	Cause	Fix
“No editable surfaces loaded.”	No surface, or only textured meshes	Clean Mesh does not edit textured OBJ meshes
Closed reads No	The surface has open edges, so its volume is unreliable	Clear Open Edges with Fill or Close
“Fill couldn’t close these — repair by hand”	The gap edges do not meet cleanly	Weld at 0.001–0.002 m, then Close, or fill in Edit Mesh
Lighting looks patchy	Triangles face different ways	Orient, or Align on an open surface
A boolean or slice fails on this surface	Open edges or crossing triangles	Clear every row, then try again

Other ways to use it

Method	Result
Right-click a surface → Clean in its properties	Opens Clean Mesh on that surface
The ⚠ volume badge on a solid in the tree → Clean	Opens Clean Mesh from the Unreliable Volume warning
One item’s own repair button	Fixes a single fault, with a before-and-after