The Simplify tool, located under the Lines tab, reduces the number of vertices and edges of a polyline while keeping its shape as close as possible to the original. Its tooltip reads "Decimate polyline - reduce the number of structural elements in the polyline while keeping the general shape close to the original."
When to Use It
Lines made by Section, Distance Map to IsoLines or Points to Lines often have far more vertices than their shape needs: a straight wall of a CAD part is cut into hundreds of short segments. Simplify such a line before you save it or process it further. For example, a section of a CAD housing had 1,076 vertices; Simplify with the default values left 49, and the length of the contour changed from 1,143.76 to 1,143.79 mm. To smooth a jagged line instead, use To Spline; to add vertices, use Subdivide. For meshes, see Simplify for meshes.
Simplify a Polyline
- Select exactly one polyline in the Scene tree.
- Open the Lines tab.
- Click Simplify.
Clicking Simplify opens a panel with the decimation settings. Max error is always visible; the other settings are under Advanced.
| Parameter | What it does | Default |
|---|---|---|
| Max error | The maximum allowed estimated distance from the original line. Decimation stops when the estimated deviation would exceed this value | 1/1000 of the line's bounding-box diagonal |
| Target edges | The minimum number of edges that should remain after decimation | 1 |
| Stabilizer | A dimensionless coefficient: higher values keep the density of the original points more closely. At 0, only the shape of the line is kept, which may produce artifacts on completely straight sections | 0.000001 |
| Longest edge length | The maximum edge length that can be created during decimation | The bounding-box diagonal |
| Optimize vertex positions | After each edge collapse, moves the remaining vertex to keep the local shape. Off: the edge collapses into one of its vertices, which keeps its position | On |
| Move boundary vertices | Allows collapsing edges at the ends of an open polyline. Off: the end vertices stay fixed | On |
Apply (or Enter) simplifies the selected line in place and closes the panel; press Ctrl+Z (Cmd+Z on macOS) to undo. A good start is Max error equal to the tolerance of your part.
Example
To make the effect easy to see, the example uses aggressive settings:
- Max error: 3 mm
- Target edges: 30
- Stabilizer: 0.000001
- Longest edge length: 40 mm
- Optimize vertex positions: on
- Move boundary vertices: off, so the end points stay fixed and the before-and-after comparison is easier to follow
After Apply, the smooth, densely sampled curve becomes more angular, but its general shape remains recognizable. The Information panel shows the change:
- Vertices: from 601 to 31.
- Edges: from 600 to 30.
- Average edge length: from about 0.563 mm to 11.309 mm.
The total line length changes only slightly, from 337.923 mm to 339.281 mm.
