STL Simplifier & Smoother (Reduce Triangles, Decimate)

See STL Simplifier & Smoother (Reduce Triangles, Decimate) in action

azrscorp.com/quickfix/stl-decimate-simplify-smooth-reduce-triangles/

1Drop in a dense STL, OBJ, 3MF or scan.

2Choose Reduce, Smooth or both and set the strength.

3Optionally set a maximum deviation in mm.

Free STL Simplifier & Smoother — Reduce Triangles Online

Photogrammetry scans, sculpts and exports from some CAD programs can contain millions of triangles — files too big to upload, slow to slice and heavy to open. This tool reduces the triangle count with quadric-error edge collapse, the same family of algorithm used in professional mesh software: it repeatedly removes the edge whose loss changes the surface least, so flat regions lose triangles first and curved, detailed regions keep them. You choose how many triangles to keep and, optionally, a maximum surface deviation in millimetres so the reduction stops before it distorts the part.

A second mode smooths rough, noisy or stair-stepped meshes using Taubin (λ|μ) smoothing, which relaxes vertices without the shrinkage of plain Laplacian smoothing, and can leave sharp edges alone above an angle you choose. You can run both in one go. The result shows triangle count, file size, volume change and whether the solid is still watertight, and you can step back to the original at any time. All processing runs in a background thread in your browser, so the page stays responsive and the model is never uploaded.

Key features

How to use it

1. Drop in a dense STL, OBJ, 3MF or scan.
2. Choose Reduce, Smooth or both and set the strength.
3. Optionally set a maximum deviation in mm.
4. Check the result in the viewer and download it.

Worked example

Example

A 400,000-triangle scan reduced to 20% keeps about 80,000 triangles; a smooth sphere or torus can lose 90% of its triangles with under 2% volume change, while a cube stops at 12 triangles because every further collapse would break its corners.

Who uses this tool

Tips for the best results

• Reduce to 20–50% for printing; the difference is invisible at 0.2 mm layers.
• Use a deviation limit of about 0.05–0.2 mm for parts that must stay accurate.
• Smooth before reducing if the scan is noisy.
• Keep the original — decimation cannot be undone after you download.

Common mistakes to avoid

• Reducing a low-poly CAD part: it has few triangles already and corners will suffer.
• Smoothing mechanical parts and rounding their sharp edges — raise the sharp-edge angle protection.
• Ignoring a not-watertight warning before printing.

Frequently asked questions