Decimating¶

In one sentence: Reduce the number of triangles in the mesh while preserving the overall shape within a specified tolerance.

Overview¶

Workbench: Mesh
Menu: Mesh → Meshes → Decimate…
Command: Mesh_Decimating
Shortcut: none

Reduces the triangle count of the mesh while trying to maintain the surface shape within a user-specified tolerance. Useful for reducing file size and improving performance on over-detailed meshes.

Intuition¶

A mesh from a fine scan or a high-resolution tessellation may have far more triangles than needed for the intended use. A 3-D printer with 0.2 mm layer height does not benefit from mesh triangles smaller than 0.2 mm — they just inflate the file size and slow down the slicer. Decimation removes redundant triangles while keeping the surface shape within the allowed tolerance.

When to use it¶

An STL from a high-resolution scan is too large for the slicer.
You need to reduce file size for web or game use.
After Smoothing, the mesh has many small triangles that represent noise that was smoothed away.

When NOT to use it¶

Don't decimate below the print resolution — if triangles become larger than 0.2 mm on a 0.2 mm layer-height printer, the mesh facets will be visible in the print.

Parameters¶

Parameter	Description
Reduction (%)	Target reduction in triangle count
Tolerance	Maximum allowable deviation from the original surface (mm)

Use Tolerance for engineering work — it maintains accuracy and stops decimating when the error limit is reached. Use Reduction % when a specific count target is needed.

Common mistakes and pitfalls¶

Aggressive decimation introduces visible facets

Reducing below 10% of the original count can make flat panels visible on smooth surfaces. For 3-D printing, ensure triangles remain smaller than your layer height after decimation.

Decimation is not reversible without undo

Decimation modifies the mesh in place. Keep a backup copy before decimating.