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geo/Decimate

Reduces the triangle count of a mesh while preserving its appearance.

Topology

Simplifies each input triangle mesh with a quadric error metric (the polyReduce operation), stopping at the requested target or when the error budget is reached, whichever comes first. Topology is preserved: a watertight mesh stays watertight, and a non-manifold mesh (a raw scan) is decimated as-is without ever failing the cook. Typical use is taming dense imports: decimate a multi-million-triangle scan before feeding remeshing or simulation nodes. Other geometry types pass through unchanged.

Parameters

Name Type What it does
mode UInt8 RATIO · TRIANGLE_COUNT How the target is expressed: as a fraction of the input triangle count, or as an absolute triangle count.
ratio Float Fraction of the input triangle count to keep (0.25 keeps a quarter of the triangles).
count UInt32 Triangle count to aim for, clamped to the input count. Useful to bring inputs of very different densities to the same budget.
maxError Float Maximum simplification error, as a fraction of the mesh extent (0.01 = 1%). The node stops simplifying once reaching the target would exceed this.
lockBoundaries Bool Keep open-boundary vertices in place (rims, cut edges), so a decimated piece still lines up with neighbouring geometry.
pruneSmallComponents Bool Remove disconnected components smaller than the error budget: scan dust and floaters.
weld Bool Merge coincident vertices first, so seamed or triangle-soup inputs (STL scans) decimate as one connected surface. An input that is already a closed manifold is left alone: welding it could only pinch it, which would cost triangles and open holes.
repair Bool Repair the simplifier's output: cancel the zero-volume face pairs it leaves, split the edges that still carry more than two faces, and only as a last resort drop a face. Turn it off to see exactly what the simplifier produced, or when a downstream node does its own repair. Editable-mesh consumers (geo/Remesh, geo/QuadRemesh) need it on.
lockGroup String A point group whose points stay exactly where they are and are never removed, such as the points on a feature line or the outline. Leave it empty to lock nothing.
importanceAttributeName AttributeName A point attribute saying which points matter, for example one built from geo/Silhouette and geo/RidgeValley. Points at or above the threshold are kept in preference to the others. Without the attribute, nothing is steered.
importanceThreshold Float Points whose importance is at least this are kept in preference. The simplifier treats importance as on or off, not as a gradient, so this is where the line is drawn.
allocator UInt8 TEMP · POOL · FLAT_POOL Which allocator backs the scratch buffers: a pool/flat-pool clears at end of cook, temp at end of frame.

Examples

Scenes you can open in the editor that teach this node.

Keep detail where it matters
Keep detail where it matters

A lumpy ball reduced to 5% of its triangles three ways: evenly, keeping more points where an importance attribute says so, and keeping a locked group of points untouched.

geo/Decimate geo/AttributeTransfer geo/AttributeDisplay geo/GroupCreate

Modeling

See also

This page is generated from the engine, so it describes the release you can download. The same text is in the editor's Help panel next to the node itself.