Concave Hull

Dependencies

This node requires SciPy library to work.

Functionality

This node generates a “Concave Hull” mesh of given set of points, by use of AlphaShape algorithm. Alpha Shape algorithm uses Delaunay triangulation to work.

In many cases, Delaunay triangulation in 3D tends to generate almost flat tetrahedrons on the boundary. This node can automatically skip generation of such tetrahedrons.

Inputs

This node has the following inputs:

• Vertices. The vertices to generate concave hull for. This input is mandatory.

• Alpha. Alpha value for the Alpha Shape algorithm. Bigger values correspond to bigger volume of the generated mesh. If the value is too small, the mesh can be non-manifold (have holes in it). The default value is 2.0.

Parameters

This node has the following parameter:

• Correct normals. If checked, the node will recalculate the normals of generated mesh, so that they all point outside. Otherwise, the orientation of faces is not guaranteed. Checked by default.

Outputs

This node has the following outputs:

• Vertices. Vertices of generated mesh.

• Edges. Edges of generated mesh.

• Faces. Faces of generated mesh.

Examples of Usage

1. Generate points on Suzanne mesh, and generate concave hull for them:

• Generator-> Suzanne

• Spatial-> Populate Mesh

• Spatial-> Lloyd on Mesh

• Viz-> Viewer Draw

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2. In some cases, together with “Dual Shape” node, this node can be used to generate Voronoi diagrams on surface of Solid or mesh objects:

• Solids-> Torus (Solid)

• Spatial-> Populate Solid

• Modifiers->Modifier Make-> Dual Mesh

• Viz-> Viewer Draw