I have a set of points from which I am trying to perform a TIN triangulation.

However, the algorithm for the triangulation (i.e. the resulting raster) creates triangles that I would like avoid for the interpolation. This is how the interpolations looks like (i.e. the resulting Delaunay triangulation):

enter image description here

I'd like to get an output like this: enter image description here

I swear I have been researching on Google to get a solution but I can't find anything! Can anyone shed some light on how to solve this?

  • This might be referred to as a constrained Delaunay triangulation. What defines your predefined area? If you have that predefined area a polygon then clip or extract the final surface as needed.
    – GBG
    Mar 15, 2023 at 16:46

1 Answer 1


The constrained area looks like a "concave hull" or "alpha shape". If you create a concave hull from the points (which, unlike a convex hull isn't trivial, it requires a tuning parameter) then crop the full triangulation to that you should approximate your desired output.

Looking at your specific data, it might be hard to get the concave hull to include the pointy bit at the top left but still go into the round bay area on the right. You might want to edit the concave hull manually if you are really fussy about what's included.

You might also want to buffer the concave hull in our out a bit to include some triangles. Here's a recipe, add salt and pepper to taste:

Point data:

enter image description here

Full delaunay triangulation:

enter image description here

Plus Concave Hull created by the Concave Hull plugin:

enter image description here

Crop Delaunay Triangle layer by concave hull to get orange triangles (purple areas are the underlying Delaunay Triangle layer):

enter image description here

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