Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
Prevent long edges in triangulation

Subject: Prevent long edges in triangulation

From: AJP

Date: 1 Jun, 2011 16:45:21

Message: 1 of 2

After triangulating my points (x,y) using delaunay(x,y) I have many undesirable long edges around the outer perimeter of the triangulation.

Is there any way to prevent these from appearing or modifying them so that edges are computed to more nearby points?

I am aware that this problem is inherent to the Delaunay Triangulation and has something to do with encroaching on the convex hull of the data, but beyond that I'm lost.

I have looked at doing a constrained triangulation, but since I have no knowledge of the points or triangulation in advance, I don't know how to specify the constraint matrix.

Any ideas would be great. Thanks to all for contributions.

Subject: Prevent long edges in triangulation

From: matt dash

Date: 1 Jun, 2011 18:50:20

Message: 2 of 2

"AJP" wrote in message <is5qb1$hmd$1@newscl01ah.mathworks.com>...
> After triangulating my points (x,y) using delaunay(x,y) I have many undesirable long edges around the outer perimeter of the triangulation.
>
> Is there any way to prevent these from appearing or modifying them so that edges are computed to more nearby points?
>
> I am aware that this problem is inherent to the Delaunay Triangulation and has something to do with encroaching on the convex hull of the data, but beyond that I'm lost.
>
> I have looked at doing a constrained triangulation, but since I have no knowledge of the points or triangulation in advance, I don't know how to specify the constraint matrix.
>
> Any ideas would be great. Thanks to all for contributions.

I dont know about computing edges to closer points, but you might be able to remove the long edges completely by calculating the alpha shape of your points (search the file exchange for this) for an appropriate value of alpha, then remove any triangles whose centroid falls outside of the alpha shape (tested using inpolygon). You might still need some prior knowledge of the points to choose a value for alpha, which basically defines what you consider to be too long of an edge.

Tags for this Thread

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us