Subdivide: split large triangles of a mesh or long line segments

Mesh Repair › Subdivide splits large triangles into smaller ones. The shape of the mesh stays the same, but the mesh gets more triangles where they were too large. You need it when a part of a mesh is too coarse for the next step, for example a hole patch made of a few large triangles that you want to smooth. The Subdivide button on the Lines tab does the same for line segments: see Subdivide lines.

When to use Subdivide

• A patch after Fill Holes. The Flat option of Fill Holes fills a hole with as few triangles as possible. Smoothing tools move vertices, and such a patch has almost none inside. Subdivide the patch first, then smooth it.
• Large triangles next to small ones, for example in a CAD export, before an operation that needs a dense surface in that area.

Subdivide only adds triangles and never removes them. To make a mesh lighter, use Simplify; to make all triangles about the same size, use Remesh.

Subdivide a mesh

1. Select one mesh in the Scene tree. Subdivide works with exactly one selected mesh.
2. Optional: select the part of the surface you want to refine. With a selection, only edges inside the selection and on its border are split, so triangles right next to the selection can be split too.
3. Open Mesh Repair › Subdivide.
4. Set Max New Vertices. To stop at a given triangle size instead, set Max Edge Length under Advanced.
5. Turn on Preview to check the result, then click Apply.

Before you start, press L to see the triangles. In this example, triangle sizes vary across the surface.

Example: a hole patch before smoothing

A real case on a scan with 403,116 triangles and 169 holes:

1. We filled one large hole with Fill Holes and the Flat option. The patch had 2,155 triangles, with vertices only along the hole border.
2. We selected the patch triangles and opened Subdivide. Max New Vertices was set to 1,608, the number of vertices of the selection. Apply split 1,608 edges in 0.3 s, and the patch grew to 4,512 triangles. Only triangles of the patch and the ones touching its border were split.
3. To match the patch to the rest of the scan, we raised Max New Vertices and set Max Edge Length under Advanced to 2.37 mm, the Avg Edge Length of the scan. The patch grew to 8,377 triangles.

Now the patch has enough vertices inside for smoothing tools such as Reduce Noise to shape it.

Settings

Subdivide splits the longest edges first (with Curvature Priority above 0%, edges in curved areas count as longer). It stops when it has added Max New Vertices vertices or when another stop condition under Advanced is met, whichever comes first.

Parameter	What it does	Default / tip
Max New Vertices	The top limit on the number of edge splits, which is also the number of new vertices	The number of vertices in the mesh, or in the selection if there is one, so the default run roughly doubles the vertex count
Curvature Priority	0% subdivides the same way everywhere. 100% makes the subdivision much finer in curved areas than in flat ones	0%

Advanced settings

Parameter	What it does	Default / tip
Smooth Mode	Puts new vertices so that they form a smooth surface together with the existing ones. Best for natural, organic surfaces	Off
Project on Original Mesh	Moves every new vertex onto the original surface. The shape can still change slightly, because Subdivide also flips edges (up to Max Angle Change)	On
Max Angle Change	An edge is flipped only if this changes the angle between the two triangles by no more than this value	30°
Min Sharp Dihedral Angle	Shown with Smooth Mode. Turns smoothing off at edges whose dihedral angle is at least this value, so sharp edges stay sharp	30°
Max Edge Length	Subdivision stops when all edges inside and on the border of the region are not longer than this value	0 (no limit). Set it to the Avg Edge Length of the mesh from the Information panel to match the patch to the rest of the surface
Max Tri Aspect Ratio	Subdivision stops when all triangles in the region have an aspect ratio at or below this value	0.999 (not used)
Critical Tri Aspect Ratio	Triangles with a larger aspect ratio are treated as degenerate, and Max Angle Change is ignored for them	10000

Preview updates the mesh while you change the parameters; it may freeze for a moment on heavy meshes. Apply runs the subdivision and closes the panel.

In this example, we applied the default settings. Large triangles are split into smaller ones, and the triangle sizes become more even across the surface. On a CAD part of 79,516 triangles, the default settings added 39,730 vertices (one per existing vertex) and gave 158,976 triangles in 0.7 s. Triangles may still differ in size depending on the local geometry, and the total triangle count goes up.

Subdivide lines

Lines › Subdivide splits long segments of a line (polyline) into shorter ones; its tooltip reads "Split large line segments on smaller ones." Use it when a line has too few points for the next step, for example before you smooth it with Reduce Noise. It needs the Professional plan.

1. Select one or more lines in the Scene tree.
2. Open Lines › Subdivide.
3. Set the parameters below and click Apply. There is no preview; the panel closes after Apply.

The longest segments are split first.

Parameter	What it does	Default
Max new vertices	The top limit on the number of segment splits and new points	The number of segments in the first selected line, so the default run roughly doubles the point count
Shortest split segment	Subdivision stops when all segments are shorter than this value	0 (no limit)
Curvature-based	Off: each new point goes to the middle of a segment, and the line keeps its exact shape. On: new points are placed on a smooth curve through the neighboring points, so the line becomes rounder. Works best for natural lines with segments of similar length and no sharp corners	Off