"Concave Hull" documentation.

2188664b · Ilya Portnov · d707d5af · 2188664b · 2188664b
--- a/docs/nodes/spatial/concave_hull.rst
+++ b/docs/nodes/spatial/concave_hull.rst
+Concave Hull
+============
+
+Dependencies
+------------
+
+This node requires SciPy_ library to work.
+
+.. _SciPy: https://scipy.org/
+
+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.
+
+.. _AlphaShape: https://en.wikipedia.org/wiki/Alpha_shape
+.. _Delaunay: https://en.wikipedia.org/wiki/Delaunay_triangulation
+
+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:
+
+.. image:: https://user-images.githubusercontent.com/284644/99681287-c8163f80-2a9f-11eb-8f30-4afd49fd338f.png
+
+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:
+
+.. image:: https://user-images.githubusercontent.com/284644/100535011-f7167900-3236-11eb-85d2-764ce1f99e6a.png
+
--- a/docs/nodes/spatial/spatial_index.rst
+++ b/docs/nodes/spatial/spatial_index.rst
@@ -21,4 +21,5 @@ Spatial
   lloyd_solid
   lloyd_solid_face
   convex_hull_mk2
+   concave_hull