Polygon mesh: what a 3D model is made of
A polygon mesh is the surface of a 3D model made up of a large number of small faces, most often triangles. The printer reads the shape of the model from it.
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What is in a mesh
A polygon mesh is a list of points in space and the faces between them. The faces are most often triangles, because a triangle is always flat and unambiguous. Thousands of triangles can build up any surface.
The STL, 3MF and OBJ formats store exactly this kind of mesh. STEP is different, it describes exact surfaces and has to be converted to a mesh before printing.
Mesh resolution
A curve in a mesh is made of straight segments. With a coarse mesh a sphere is visibly faceted, with a fine one it looks smooth. A very fine mesh makes the file bigger, and we accept files up to 50 MB, but it prints just the same.
If you export from CAD, set the resolution so that curves have no visible edges. A good test is a shape that still looks smooth when you zoom in on screen.
What a mesh has to satisfy
- Be closed. No holes, so it is clear what is inside. See manifold model.
- Have correct face directions. The normals must point outwards.
- Not intersect itself. Overlapping faces cause errors.
The mesh and your order
After you upload, we prepare the model on our server and repair small holes in the mesh automatically. For bigger errors we will write to you, see model repair. A mesh from a 3D scan or digital sculpting can have millions of triangles, but that does not bother the printer.
Common questions
What is a mesh?
The surface of a 3D model made of triangles. Both STL and 3MF store exactly such a mesh.
How many triangles should a model have?
Enough that curves do not look visibly faceted. For printing, a file under 50 MB matters more than the triangle count.
Why is STEP not a mesh?
STEP stores exact surfaces and curves. It has to be converted to a mesh before printing.
Related terms
Manifold (watertight model)
A manifold model is a 3D model whose surface has no holes or overlapping faces, so it is clear what is inside and what is outside.
Model repair
Model repair means editing a polygon mesh to close holes, fix flipped faces and remove self-intersections, so the model can be printed.
STL
STL is the most common file format for 3D printing. It describes only the surface of a model as a mesh of triangles, with no colours, material or units.
3MF
3MF is a 3D printing file format that carries units, colours, materials and several parts as well as the shape of the model. It succeeds STL and is the best choice for multicolour printing.
OBJ
OBJ is an open 3D model format that describes the surface as a mesh of polygons and can refer to materials and textures. Graphics programs and 3D scanners commonly export it.
STEP
STEP is the standard format for exchanging 3D models between CAD programs, defined by ISO 10303. Unlike STL it describes exact geometry with curves and surfaces, not a mesh of triangles.
SourcesSources checked 1 November 2026, 2
- Polygon mesh, Wikipedia, checked 2026-11-01
- Triangle mesh, Wikipedia, checked 2026-11-01
We will print it for you
Upload a model and see the price per piece, the total with shipping and the date at once. We print in Košice, Slovakia, from PLA and PETG.
No model? No problem, pick a ready one
These sites have thousands of free models. Download an STL or 3MF and upload it here. If you sell it or use it for business, check the model licence. How to pick a model and licence