Added vtkCenterOfArea and vtkCenterOfVolume

Author: Steffen Schuler

.gitignore

@@ -2,3 +2,4 @@
 build/
 *.mex*
 *.m~
+*.asv

MATLAB/remeshTriangleMesh.m

@@ -28,8 +28,7 @@
     instantmeshes = '/Applications/Instant Meshes.app/Contents/MacOS/Instant Meshes';
 end
 if ~exist(instantmeshes, 'file')
-    instantmeshes = '/Users/ss029/Applications/Instant Meshes.app/Contents/MacOS/Instant Meshes';
-%     instantmeshes = '/Volumes/ServerApps/Instant Meshes.app/Contents/MacOS/Instant Meshes';
+    instantmeshes = '/Volumes/ServerApps/Instant Meshes.app/Contents/MacOS/Instant Meshes';
 end
 if ~exist(instantmeshes, 'file')
     error('Instant Meshes could not be found.');

MATLAB/vtkCenterOfArea.m

@@ -0,0 +1,27 @@
+% Computes the center of area (center of mass of a surface, assuming 
+% uniform density) of a triangle mesh.
+% Relies on gptoolbox by Alec Jacobson.
+%
+% Syntax:
+% [centerOfArea,area,a] = vtkCenterOfArea(inStruct)
+%
+% Written in 2020 by Steffen Schuler
+% Institute of Biomedical Engineering, KIT
+% www.ibt.kit.edu
+
+function [centerOfArea,area,a] = vtkCenterOfArea(inStruct)
+
+P = double(inStruct.points);
+C = inStruct.cells;
+
+if size(C,2) ~=3
+    error('This function can only be applied to triangle meshes.');
+end
+
+centroids = squeeze(mean(reshape(P(C,:),[],size(C,2),size(P,2)),2));
+a = doublearea(P,C)/2;
+area = sum(a);
+
+centerOfArea = sum(repmat(a,1,3) .* centroids, 1) ./ area;
+
+end

MATLAB/vtkCenterOfVolume.m

@@ -0,0 +1,43 @@
+% Computes the center of volume (center of mass assuming uniform density)
+% of a tetrahedral mesh or a closed triangle mesh.
+% Relies on gptoolbox by Alec Jacobson.
+%
+% Syntax:
+% [centerOfVolume,volume,v] = vtkCenterOfVolume(inStruct)
+%
+% Written in 2020 by Steffen Schuler
+% Institute of Biomedical Engineering, KIT
+% www.ibt.kit.edu
+
+function [centerOfVolume,volume,v] = vtkCenterOfVolume(inStruct)
+
+P = double(inStruct.points);
+C = inStruct.cells;
+
+dim = size(C,2);
+if dim == 3
+    P = [P; mean(P,1)];
+    C = [C repmat(size(P,1), size(C,1), 1)];
+end
+
+a = P(C(:,1),:);
+b = P(C(:,2),:);
+c = P(C(:,3),:);
+d = P(C(:,4),:);
+v = dot(a-d, cross(b-d, c-d, 2), 2)./6;
+volume = sum(v);
+
+if dim == 3
+    d0 = repmat([0 0 0], size(C,1), 1);
+    v0 = dot(a-d0, cross(b-d0, c-d0, 2), 2)./6;
+    volume0 = sum(v0);
+    if abs(volume-volume0) > 1e-5
+        warning('The surface is not closed.');
+    end
+end
+
+centroids = squeeze(mean(reshape(P(C,:),[],size(C,2),size(P,2)),2));
+
+centerOfVolume = sum(repmat(v,1,3) .* centroids, 1) ./ volume;
+
+end