# Trouble triangulating a surface

2 views (last 30 days)
David Winthrop on 5 Dec 2019
Commented: darova on 5 Dec 2019
I have attached a text file with the data I am discussing.
I need to triangulate this data so that I can write the triangulation to an stl file using stlwrite (from the file exchange). The problem is that this sequence produces triangles that are NOT in the plane for seemingly no reason. As can be seen, all of the points are in a circle. How can I triangulate this surface without the wierd out of plane triangles appearing??
>> D = importdata('Endcap.txt');
>> TRI = delaunay(D(:,1),D(:,2),D(:,3));
>> trisurf(TRI,D(:,1),D(:,2),D(:,3))
>> hold on
>> plot3(D(:,1),D(:,2),D(:,3),'*r')
Note that I expected something like this:
>> surf([D(:,1),repmat(mean(D(:,1)),length(D),1)],[D(:,2),repmat(mean(D(:,2)),length(D),1)],[D(:,3),repmat(mean(D(:,3)),length(D),1)])

darova on 5 Dec 2019
try alphaShape for triangulating
David Winthrop on 5 Dec 2019
Thank you but this didn't do the trick.
For example:
>> Du = unique(D,'rows');
>> TRI = alphaShape(Du(:,1),Du(:,2),Du(:,3));
>> trisurf(TRI.Points,Du(:,1),Du(:,2),Du(:,3))
Error using patch
Value must be of numeric type and greater than 1
Error in trisurf (line 91)
h = patch('faces',trids,'vertices',[x(:) y(:) z(:)],'facevertexcdata',c(:),...
darova on 5 Dec 2019
I don't have alphaShape
Try
plot(TRI)
see HELP

R2019a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!