GLOSSARY
Mesh Decimation
Mesh decimation is the process of reducing the number of triangles in a mesh while keeping the overall shape recognizable. The standard algorithms — quadric edge collapse and clustering — preserve silhouette better than naive uniform reduction.
Definition
Decimation algorithms iteratively merge or remove triangles based on a quality metric. Quadric edge collapse — the most common — repeatedly chooses the edge whose collapse introduces the least geometric error and merges its endpoints into one vertex. The mesh shrinks by one triangle per iteration.
MeshLab, Blender (the Decimate modifier), and Open3D all implement quadric decimation. You typically specify either a target triangle count or a percentage reduction.
Why it matters
Decimation is the right tool when you have a heavyweight mesh you do not need at full resolution: a 5-million-triangle scan you want to ship as a 200k-triangle web preview, or a high-detail STL whose file size is causing problems for an older slicer.
For 3D printing, decimation rarely improves outcomes. Slicers rasterize the mesh at the printer's resolution; if your mesh is well-sized for the part, decimating loses fine detail for no benefit. Use it only when file size or memory is the actual bottleneck.
Common confusion
Decimation does not produce clean quad topology. The result is still a triangle soup, just a sparser one. For animation or sculpting workflows, you want retopology instead.
Aggressive decimation can break manifold properties — collapsing two non-adjacent edges into the same vertex creates non- manifold geometry. Verify the result before slicing.