| Zero-area faces | Faces with no area at all: three points on a line, or repeated points. They carry no surface and break normals, UVs and booleans. Clean removes them. |
| Sliver faces | Extremely thin, needle-like triangles. Legal geometry, but they wreck shading and make remeshing and simulation unstable. |
| Boundary edges | Edges with only one face attached (the rim of a hole). Any non-zero count means the mesh is not watertight, so it can't be 3D printed or used in a volume boolean. Fill Hole seals them. |
| Non-manifold edges | Edges shared by three or more faces, so the surface branches. No real solid can do this; it blocks watertight fills and booleans. Clean resolves them. |
| Non-manifold vertices | Vertices where two otherwise separate patches of surface meet at a single point (a bow-tie). The surface pinches to nothing there. Clean resolves them. |
| Crease edges | Edges where the UV layout is cut, so the two sides land in different places in the atlas. Expected wherever a model was unwrapped. A high count means a fragmented atlas. |
| UV seam edges | The edges along which the texture layout is cut into charts, with their total length in the model's units. A reduction pulls these out of line unless told otherwise; a Seams importance above 1 on Decimate, Remesh or LOD Set holds them. Reads n/a when the model carries no UVs. The viewer's Protected edges overlay draws them in teal. |
| Material boundary edges | The edges where one material meets another, with their total length in the model's units. A Materials importance above 1 on Decimate, Remesh or LOD Set holds them on their line. Reads n/a when the model carries a single material or none. The viewer's Protected edges overlay draws them in magenta. |
| Symmetry | Whether the model is a mirror image of itself across one of the three coordinate planes, judged on a sample of its vertices: the plane (YZ for left and right), where it sits when it is off the origin, and the share of sampled vertices that have a mirror image. A character or vehicle authored symmetrically reads close to 100%. Decimate and LOD Set can then keep the two halves identical through the reduction with their Symmetry setting, which finds the plane again on the full model. The viewer's Protected edges overlay draws the edges lying on the plane in gold. |
| Corner vertices | Vertices where several sharp feature edges meet. Remesh and Quad Mesher pin these in place, so they mark where hard detail is preserved. |
| Connected components | How many separate pieces the mesh is made of. More than one means loose parts. Combine can sew them together or drop them. |
| Debris parts | Separate pieces that are tiny next to the whole model: scan crumbs, stray triangles, floaters. Combine's Remove debris strategy drops exactly these, so the count predicts what that node would remove. The largest piece never counts. |
| Self-intersections | Pairs of faces where one surface passes through itself: folded-over surfaces, scan overlap. They break booleans, voxelization and printing. Clean with resolve self-intersections on repairs them; a very large count is rebuilt more reliably by Voxelize. Separate parts passing through each other are counted under Overlapping parts instead. Shows 'skipped' when the model is over the browser's face budget for this query. |
| Overlapping parts | Pairs of faces where two separate parts of the model pass through each other: a candle pushed into its holder, parts of an assembly modelled overlapping. This is how many models are built, not a defect: it renders and bakes correctly, so Clean leaves it as it is. Shows 'skipped' when the model is over the browser's face budget for this query. |
| Flipped faces | Faces wound the wrong way: either inside-out against their neighbours, or a whole closed shell wound inward. Zero on a consistently outward mesh. These are the faces Conform Normals would flip, so a non-zero count means that node is worth adding; a zero means it can be skipped. |
| Double wall | The surface carries a redundant second skin (an outer skin and an inner skin, fused into one sheet or nested inside) rather than one solid surface. Image-to-3D generators (Trellis and similar) emit these, at any gap between the skins. Downstream it doubles the faces Decimate must spend, makes Voxelize read the model as hollow, and confuses baking. Visual Hull removes the hidden inner skin. Only a hidden, layered skin counts: open scenes, ground planes and double-sided sheets do not qualify, and a shell shredded open by holes waits for Fill Hole to close it first. |
| Hidden interior | A large share of the surface is buried inside other parts of the model: frames inside furniture, the cabin of a vehicle, parts stacked inside a housing. This is how assemblies are built, not a defect, and it is different from a double wall (one surface doubled onto itself). The drafts that reduce a model (Reduce, Reduce & Bake, Retopo and the platform drafts) add a Visual Hull when they see it, so the face budget is not spent on geometry nobody can see. Fix & Clean leaves the interior alone: a repair should not delete the inside of your model. |
| Enclosed volume | How much of the volume the surface sweeps it actually encloses. A solid encloses most of it; a tight double wall encloses only the sliver between its skins; a double-sided sheet encloses nothing. Supporting evidence beside the double-wall verdict, not the verdict itself. n/a means every face was degenerate. |