Glossary · Data

3D printing

Mesh (triangle mesh)

The surface of a 3D model, made up of a great many small triangles. This is how STL, 3MF and OBJ files store their shape.

Explained in more detail

A mesh describes a shape only through its surface: vertices connected into triangles. The more triangles, the smoother curves look and the larger the file becomes. For printing, a mesh must be closed, meaning without holes and without faces that intersect themselves, so that the slicer can tell inside from outside (known as manifold). A mesh is easy to print but hard to edit: enlarging a hole precisely is laborious in a mesh, but easy in a CAD format such as STEP. Scans first produce a point cloud, from which the software calculates a mesh.

Where does the term come from?

English mesh means net or netting. In computer graphics one speaks of a polygon mesh, a net of polygons; in 3D printing these are almost always triangles.

In practice

• Reduce the triangle count of large scans just enough that the necessary details are preserved. This makes files smaller and slicers faster.
• You repair open or faulty meshes with MeshLab or the 3D Print Toolbox in Blender, which closes open areas with "Make Manifold".
• STL and OBJ do not store a unit. Check after import whether the dimensions are right.
• If you want to change dimensions later, design the part in CAD software and only export a mesh at the end.

Not to be confused

Not to be confused with the mesh in auto bed levelling: there it means a grid of height measurement points on the build plate, not a 3D model.

Frequently asked questions

What does manifold mean?

A mesh is manifold, colloquially watertight, if it forms a closed shell without holes, open edges or intersecting faces. Only then can the slicer determine unambiguously what is inside and what is outside.

Why is a mesh difficult to edit?

A mesh knows no holes, radii or dimensions, only triangles. For precise changes you need the design file, for example as STEP, or you rebuild the part in CAD.