# Creating complex concave polygonal surface from points

**URL:** https://discourse.vtk.org/t/creating-complex-concave-polygonal-surface-from-points/10959
**Category:** Support
**Tags:** python
**Created:** [March 14, 2023, 4:09am UTC](https://discourse.vtk.org/t/creating-complex-concave-polygonal-surface-from-points/10959 "2023-03-14T04:09:55Z")
**Posts on this page:** 1
**Showing post:** 2

<div class="post-metadata">

### Author: ![rexthor](https://discourse.vtk.org/user_avatar/discourse.vtk.org/rexthor/32/6481_2.png) [@rexthor](https://discourse.vtk.org/u/rexthor)
#### Post date: [March 14, 2023, 2:58pm UTC](https://discourse.vtk.org/t/creating-complex-concave-polygonal-surface-from-points/10959/2 "2023-03-14T14:58:58Z")

</div>

I think Delaunay triangulation will always give you a convex hull. I’m not a mathematician, but `vtkDelaunay2D` (or anything that uses Delaunay triangulation) will always give you a convex output.

There are probably algorithms that will work for you, but I think that all of them will need for you to give them hints about what is “inside” and “outside” for your polygon. That might be something like a signed distance function, or distance gradients evaluated at the polygon points.

This may only be semi-related to what you were looking for, but there are lots of other posts here that may have hints, such as: [How to triangulate a surface from point cloud - #4 by Paulo\_Carvalho](https://discourse.vtk.org/t/how-to-triangulate-a-surface-from-point-cloud/2240/4).

---

_[View the full topic](https://discourse.vtk.org/t/creating-complex-concave-polygonal-surface-from-points/10959)._