Select Region: segment a mesh by marking seed triangles

Select Region selects one region of a mesh, such as the head of a figurine scan or a boss on a CAD part, when its border is hard to draw by hand. You mark a few triangles that belong to the region and a few that do not, and MeshInspector finds the border between them along the surface. To split a whole mesh into parts automatically, use Partitioner instead.

Select a region

1. Select one mesh in the Scene tree and click Select › Select Region. While the panel is open, the mesh is shown white, without its colors or texture.
2. Mark a few triangles inside the region with the selection tools at the top of the panel: Lasso, Rect, Polygon, Brush or Pick.
3. Click Select Region Part. The selected triangles become region seeds and turn green.
4. Mark a few triangles that must stay outside the region and click Select not Region. They become not-region seeds and turn gray.
5. Optionally, choose Curvature Preference (see the table below).
6. Click Select. MeshInspector finds the border between the green and gray seeds and selects the region.

In this example, a few triangles on the side of a cylindrical part are selected (red) before Select Region Part:

After Select Region Part, they become green region seeds:

The base of the part is then marked as the not-region and shown in gray:

The seeds do not have to touch the border: a few strokes well inside the region and well outside it are enough. If the border runs in the wrong place, add seeds closer to where it should be and click Select again.

Select Region Part and Select not Region replace the seeds with the current selection. To add triangles to the seeds, click Back next to the button: the seeds turn back into selected triangles, you can add or remove triangles, and then click the button again.

The selection tools work as in Select Primitives. In this tool, Select Only Visible Triangles is on by default. The hint at the bottom of the panel calls these tools Face Selector.

Let MeshInspector choose the not-region

If you clear Manually Select not Region Part, you mark only the region seeds:

1. Clear Manually Select not Region Part. The Uncertainty Distance field appears instead of Select not Region.
2. Set Uncertainty Distance: the border will be searched no farther than this distance from the region seeds. The default is 5% of the diagonal of the mesh bounding box.
3. Select the region triangles and click Select Region Part. All triangles farther than Uncertainty Distance from them become not-region seeds.
4. Click Select.

Set Uncertainty Distance before you click Select Region Part: the not-region is computed at that moment.

Settings

Setting	What it does	Default
Manually Select not Region Part	On: you mark the not-region seeds yourself. Off: MeshInspector takes every triangle farther than Uncertainty Distance from the region seeds	On
Uncertainty Distance	Shown only when Manually Select not Region Part is off. The distance between the region seeds and the automatic not-region	5% of the bounding box diagonal
Curvature Preference	Geodesic selects the shortest border. Convex allows a longer border that runs through convex areas. Concave allows a longer border that runs through concave areas, such as the groove between a head and a body	Geodesic

After the selection

The region stays selected after you close the panel, and the mesh gets its colors back. Then:

• click Select › Selection to Object to copy the region into a new object, see Selection to Object;
• click Select › Delete Selected to delete the region from the mesh, see Delete Selected.

Here, the region found by Select is selected in red, and Selection to Object makes a new object from it; the original object is hidden: