Decimator

from ArtisanPlugin.Scripting import MeshApi as mesh

Repaired and scanned meshes are heavy — millions of faces that slow down slicers, viewers and file transfers. Two reducers, with opposite priorities: Decimate hits a face count and lets the shape suffer; DecimateToTolerance guarantees the shape stays within a deviation budget and takes whatever face count falls out. For final delivery of jewellery geometry, the tolerance-driven one is usually the right tool.

Both replace each mesh in place, keeping its Guid, so wrap the calls in a Transaction. In both, objectIds = None (or empty) means the current selection, and non-mesh objects are skipped silently.

Decimate

Rhino’s quadric edge-collapse reduction (the ArtisanMeshDecimate command, headless). Distortion is allowed: the reducer prioritises hitting the target face count over shape fidelity, so heavy percentages give a faceted low-poly look.

r = mesh.Decimate(objectIds = None, percentage = 50)

Parameter	Default	Meaning
objectIds	None = current selection	Meshes to decimate
percentage	50	Faces to remove, 1–99. percentage = 80 keeps 20% of the faces

The target is floored at 4 faces, so a tiny mesh never collapses to nothing. A mesh whose reduction fails is skipped and simply not counted.

Returns a DecimateResult with the totals, so the script can report “N meshes: X faces → Y faces”:

Field	Type	Meaning
MeshesDecimated	int	Meshes actually replaced
FacesBefore	int	Total faces across those meshes, before
FacesAfter	int	Total faces after

Validation that throws:

• Out-of-range percentage: "Percentage must be between 1 and 99."
• No meshes at all: "Nothing to decimate: select (or pass) at least one mesh."

DecimateToTolerance

Reduces each mesh as much as a deviation budget allows (the ArtisanMeshDecimateTolerance command, headless): the mesh is taken to the heaviest reduction whose result still stays within toleranceMm of the original surface. The shape is guaranteed; the face count is whatever falls out.

r = mesh.DecimateToTolerance(objectIds = None, toleranceMm = 0)

Parameter	Default	Meaning
objectIds	None = current selection	Meshes to decimate
toleranceMm	0 = 0.05	Maximum deviation from the original surface, in millimetres, regardless of the document’s units. Valid range 0.001–100

A mesh that cannot lose even one percent within the tolerance is left untouched and counted in MeshesUnchanged — the call never makes a mesh worse than the budget just to shrink it.

Returns a DecimateToleranceResult:

Field	Type	Meaning
MeshesDecimated	int	Meshes replaced
MeshesUnchanged	int	Meshes left untouched because nothing fit the budget
TrianglesBefore	int	Total triangles before, across the decimated meshes
TrianglesAfter	int	Total triangles after
MaxDeviationMm	float	Largest deviation across every decimated mesh (mm) — always ≤ toleranceMm

The counts are in triangles, not faces: the reducer triangulates quads first, so a quad mesh’s face count is not comparable with the result’s.

Validation that throws:

• Out-of-range tolerance: "Tolerance must be between 0.001 and 100 mm."
• No meshes at all: "Nothing to decimate: select (or pass) at least one mesh."

from ArtisanPlugin.Scripting import MeshApi as mesh, Transaction

with Transaction.Begin("Decimate for delivery"):
    r = mesh.DecimateToTolerance(toleranceMm = 0.05)
    print(f"{r.MeshesDecimated} meshes: {r.TrianglesBefore} -> {r.TrianglesAfter} triangles, "
          f"max deviation {r.MaxDeviationMm:.3f} mm ({r.MeshesUnchanged} unchanged)")