# triSurfRemoveThreeConnect

Below is a demonstration of the features of the `triSurfRemoveThreeConnect` function

## Contents

```
clear; close all; clc;
```

Plot settings

```
fontSize=10;
faceColor='b';
faceAlpha=1;
edgeColor=0.3*ones(1,3);
edgeWidth=2;
markerSize=5;
```

Creating example geometry

```
[F,V]=geoSphere(2,1);
indRand=randperm(size(F,1),round(size(F,1)/5));
L=false(size(F,1),1);
L(indRand)=1;
C=double(L);
% Create mid-triangle coordinates and subtriangles
[Fn,Vn]=subTriCentre(F,V,L);
Ln=false(size(Fn,1),1); Ln(end-nnz(L)*3:end)=1;
Cn=double(Ln);
```

## Removing "3-connected" vertices and replacing associated faces

In a surface triangulation "3-connected" locations often contain poor quality triangles of a locally smaller area then the rest of the surface. Smoothening does not resolve this issue since the quality is not great improved even after vertex is at the centre of its neighbouring nodes. Hence the function triSurfRemoveThreeConnect instead removes the central nodes and groups the affected triangles into a single triangle.

[Ft,Vt,Ct]=triSurfRemoveThreeConnect(Fn,Vn,Cn);

Plotting results

hf=cFigure; hold on; subplot(1,2,1); title('Surface containing split triangles','FontSize',fontSize); xlabel('X','FontSize',fontSize); ylabel('Y','FontSize',fontSize); zlabel('Z','FontSize',fontSize); hp=patch('Faces',Fn,'Vertices',Vn,'FaceColor','flat','CData',Cn,'FaceAlpha',faceAlpha,'lineWidth',edgeWidth,'edgeColor',edgeColor); set(gca,'FontSize',fontSize); view(3); axis tight; axis equal; axis vis3d; axis off; colormap autumn; camlight('headlight'); lighting flat; drawnow; subplot(1,2,2); title('Restored surface','FontSize',fontSize); xlabel('X','FontSize',fontSize); ylabel('Y','FontSize',fontSize); zlabel('Z','FontSize',fontSize); hp=patch('Faces',Ft,'Vertices',Vt,'FaceColor','flat','CData',Ct,'FaceAlpha',faceAlpha,'lineWidth',edgeWidth,'edgeColor',edgeColor); % [hp]=patchNormPlot(Ft,Vt,0.25); set(gca,'FontSize',fontSize); view(3); axis tight; axis equal; axis vis3d; axis off; colormap autumn; camlight('headlight'); lighting flat; drawnow;

* GIBBON* www.gibboncode.org

*Kevin Mattheus Moerman*, gibbon.toolbox@gmail.com

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License: https://github.com/gibbonCode/GIBBON/blob/master/LICENSE

GIBBON: The Geometry and Image-based Bioengineering add-On. A toolbox for image segmentation, image-based modeling, meshing, and finite element analysis.

Copyright (C) 2019 Kevin Mattheus Moerman

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