View License

Download apps, toolboxes, and other File Exchange content using Add-On Explorer in MATLAB.

» Watch video

Highlights from

5.0 | 1 rating Rate this file 12 Downloads (last 30 days) File Size: 4.63 KB File ID: #43013 Version: 1.2
image thumbnail



Sven (view profile)


09 Aug 2013 (Updated )

Aligns adjacent faces in a triangulated mesh surface or volume

| Watch this File

File Information

UNIFYMESHNORMALS Aligns mesh normals to all point in a consistent direction.

F_OUT = UNIFYMESHNORMALS(F,V) takes an N-by-3 array of faces F, and
returns an equivalent set of faces F_OUT with all adjacent faces in F_OUT
pointing in a consistent direction. Vertices V are also required in "in"
or "out" face alignment is specified (see below).

FV_OUT = UNIFYMESHNORMALS(FV) instead take a structure array with field
"faces" (and "vertices"), returning that structure with adjacent faces
aligned consistently as above.

[F_OUT, FLIPPED] = UNIFYMESHNORMALS(...) also returns FLIPPED, an N-by-1
logical mask showing which faces in F/FV were flipped during unification.

[...] = UNIFYMESHNORMALS(...,'alignTo','in')
[...] = UNIFYMESHNORMALS(...,'alignTo','out')
[...] = UNIFYMESHNORMALS(...,'alignTo',FACE) allows the user to specify a
single trusted FACE number which will remain unflipped, and all other
faces will be aligned to it. FACE may also be the string 'in' or 'out'.
'in' will result in all faces aligned, with direction towards the center
of the object. 'out' will result in directions pointing outwards.

      tmpvol = zeros(20,20,20); % Empty voxel volume
      tmpvol(5:15,8:12,8:12) = 1; % Turn some voxels on
      tmpvol(8:12,5:15,8:12) = 1;
      tmpvol(8:12,8:12,5:15) = 1;
      fv = isosurface(tmpvol, 0.99); % Create the patch object
      % Display patch object normal directions
      facets = fv.vertices';
      facets = permute(reshape(facets(:,fv.faces'), 3, 3, []),[2 1 3]);
      edgeVecs = facets([2 3 1],:,:) - facets(:,:,:);
      allFacNorms = bsxfun(@times, edgeVecs(1,[2 3 1],:), edgeVecs(2,[3 1 2],:)) - ...
          bsxfun(@times, edgeVecs(2,[2 3 1],:), edgeVecs(1,[3 1 2],:));
      allFacNorms = bsxfun(@rdivide, allFacNorms, sqrt(sum(allFacNorms.^2,2)));
      facNorms = num2cell(squeeze(allFacNorms)',1);
      facCents = num2cell(squeeze(mean(facets,1))',1);
      facEdgeSize = mean(reshape(sqrt(sum(edgeVecs.^2,2)),[],1,1));
      patch(fv,'FaceColor','g','FaceAlpha',0.2), hold on, quiver3(facCents{:},facNorms{:},facEdgeSize), view(3), axis image
      title('All normals point IN')
      % Turn over some random faces to point the wrong way
      flippedFaces = rand(size(fv.faces,1),1)>0.75;
      fv_turned = fv;
      fv_turned.faces(flippedFaces,:) = fv_turned.faces(flippedFaces,[2 1 3]);
      figure, patch(fv_turned,'FaceColor','flat','FaceVertexCData',double(flippedFaces))
      colormap(summer), caxis([0 1]), view(3), axis image
      % Fix them to all point the same way
      [fv_fixed, fixedFaces] = unifyMeshNormals(fv_turned);
      figure, patch(fv_fixed,'FaceColor','flat','FaceVertexCData',double(xor(flippedFaces,fixedFaces)))
      colormap(summer), caxis([0 1]), view(3), axis image


Required Products MATLAB
MATLAB release MATLAB 8.1 (R2013a)
Tags for This File   Please login to tag files.
Please login to add a comment or rating.
Comments and Ratings (1)
10 Aug 2013 Scott

Scott (view profile)

15 Aug 2013 1.1

Added ability to align faces to point 'in' or 'out' from an object

11 Sep 2013 1.2

Added more robust 'in' vs 'out' alignment via calculated mesh volume.

Contact us