Convex Hull creates the smallest convex closed mesh that contains the selected mesh or point cloud, like a film stretched tightly over its outermost points. Use it when you need the overall envelope of an object rather than its detailed shape:
- to see the space a part occupies, for example when you plan how parts fit on a build plate or in a box;
- to compare the volume of the envelope with the volume of the part in the Information panel;
- to get a simple closed body around a point cloud or an open scan surface.
How to create a convex hull
- Select exactly one mesh or one point cloud in the Scene tree.
- Click Mesh Edit › Convex Hull. The same button is on the Points tab.
The tool has no settings and works at once. The result is a new mesh named after the source with "convex hull" at the end, for example Points convex hull. It is placed exactly over the source, shown with flat shading and selected; the source object stays visible and is unselected.
Keep in mind that a convex hull keeps nothing of the inner shape: concave areas, grooves, holes and inner cavities are all bridged by flat faces. The hull usually has far fewer triangles than the source, because it only connects the outermost points.
Example: a mesh
A mesh with detailed outer geometry, including teeth, a central hole and surface contours, is selected in the Scene tree:
After Convex Hull, the new mesh is selected in the Scene tree, and both objects are visible, so you can compare their shapes:
Hide the source mesh in the Scene tree to see only the hull. The teeth and the central hole are gone: the hull is a simple convex body.
Example: a point cloud
For a point cloud, Convex Hull gives a closed mesh around all the points. Here the hull of a scanned part is shown semi-transparent over the points. The Information panel shows its size, volume and number of triangles:
A convex hull is not a surface reconstruction: to turn a point cloud into a mesh that follows its shape, see How to turn point clouds into a mesh.
