Compute perimeter 3d.

RunExample.m

@@ -147,11 +147,14 @@ for i = 1 : n_objects
     o = objects( i );
     
     area = area3d( o.boundary );
+    perim = perimeter3d( o.boundary );
+    
+    objects( i ).area = area;
+    objects( i ).perimeter = perim;
     
     uncorr = struct();
     uncorr.area = polyarea( o.boundary(:,1), o.boundary(:,2) );
-    
-    objects( i ).area = area;
+    uncorr.perimeter = perimeter3d( o.boundary( :, 1:2 ) );
     objects( i ).uncorr = uncorr;
     
 end
@@ -181,7 +184,10 @@ for i = 1 : n_objects
     
     o = objects( i );
     P = o.boundary;
-    patch( P(:,1), P(:,2), P(:,3), o.area / o.uncorr.area, ...
+    
+    err = o.perimeter / o.uncorr.perimeter - 1;
+    
+    patch( P(:,1), P(:,2), P(:,3), err, ...
         'LineWidth', 2 );
     text( o.center(1), o.center(2), o.center(3) + 0.5, num2str( i ), ...
         'HorizontalAlignment', 'center', ...

src/perimeter3d.m

+function perim = perimeter3d( p )
+%PERIMETER3D Perimeter of a closed N-dimensional polygon.
+%   p can be a N x d matrix, with d being the dimensionality.
+
+    p2 = [ p ; p( 1, : ) ];
+    p_diff = diff( p2 );
+
+    p_diff_2 = p_diff .* p_diff;
+    p_diff_2_sum  = sum( p_diff_2, 2 );
+    sls = sqrt( p_diff_2_sum );
+    perim = sum( sls );
+
+end
+