checkMeshAdjacentFaces

CHECKMESHADJACENTFACES Check if adjacent faces of a mesh have similar orientation.

   checkMeshAdjacentFaces(VERTICES, EDGES, FACES)
   The functions returns no output, but if two faces share a common edge
   with the same direction (meaning that adjacent faces have normals in
   opposite direction), a warning is displayed. 
   
   Example
   [v e f] = createCube();
   checkMeshAdjacentFaces(v, e, f);
   % no output -> all faces have normal outwards of the cube

   v = [0 0 0; 10 0 0; 0 10 0; 10 10 0];
   e = [1 2;1 3;2 3;2 4;3 4];
   f = [1 2 3; 2 3 4];
   checkMeshAdjacentFaces(v, e, f);
      Warning: Faces 1 and 2 run through the edge 3 (2-3) in the same direction

   See also
     meshes3d, trimeshMeanBreadth

0001 function checkMeshAdjacentFaces(vertices, edges, faces)
0002 %CHECKMESHADJACENTFACES Check if adjacent faces of a mesh have similar orientation.
0003 %
0004 %   checkMeshAdjacentFaces(VERTICES, EDGES, FACES)
0005 %   The functions returns no output, but if two faces share a common edge
0006 %   with the same direction (meaning that adjacent faces have normals in
0007 %   opposite direction), a warning is displayed.
0008 %
0009 %   Example
0010 %   [v e f] = createCube();
0011 %   checkMeshAdjacentFaces(v, e, f);
0012 %   % no output -> all faces have normal outwards of the cube
0013 %
0014 %   v = [0 0 0; 10 0 0; 0 10 0; 10 10 0];
0015 %   e = [1 2;1 3;2 3;2 4;3 4];
0016 %   f = [1 2 3; 2 3 4];
0017 %   checkMeshAdjacentFaces(v, e, f);
0018 %      Warning: Faces 1 and 2 run through the edge 3 (2-3) in the same direction
0019 %
0020 %   See also
0021 %     meshes3d, trimeshMeanBreadth
0022 %
0023 
0024 % ------
0025 % Author: David Legland
0026 % e-mail: david.legland@inra.fr
0027 % Created: 2010-10-06,    using Matlab 7.9.0.529 (R2009b)
0028 % Copyright 2010 INRA - Cepia Software Platform.
0029 
0030 % the message pattern that is displayed when an inconsistency is encountered
0031 pattern = 'Faces %d and %d run through the edge %d (%d-%d) in the same direction';
0032 
0033 % If edges are not specified, compute them
0034 if nargin == 2
0035     faces = edges;
0036     edges = meshEdges(vertices, faces);
0037 end
0038 
0039 % compute edges to faces map
0040 edgeFaces = meshEdgeFaces(vertices, edges, faces);
0041 Ne = size(edgeFaces, 1);
0042 
0043 for i = 1:Ne
0044     % indices of extreimty vertices
0045     v1 = edges(i, 1);
0046     v2 = edges(i, 2);
0047     
0048     % index of adjacent faces
0049     indF1 = edgeFaces(i, 1);
0050     indF2 = edgeFaces(i, 2);
0051     
0052     % if one of the faces has index 0, then the edge is at the boundary
0053     if indF1 == 0 || indF2 == 0
0054         continue;
0055     end
0056     % vertices of adjacent faces
0057     face1 = meshFace(faces, indF1);
0058     face2 = meshFace(faces, indF2);
0059     
0060     % position of vertices in face vertex array
0061     ind11 = find(face1 == v1);
0062     ind12 = find(face1 == v2);
0063     ind21 = find(face2 == v1);
0064     ind22 = find(face2 == v2);
0065     
0066     % check if edge is traveled forward or backard
0067     direct1 = (ind12 == ind11+1) | (ind12 == 1 & ind11 == length(face1));
0068     direct2 = (ind22 == ind21+1) | (ind22 == 1 & ind21 == length(face2));
0069     
0070     % adjacent faces should travel the edge in opposite direction
0071     if direct1 == direct2
0072         warning(pattern, indF1, indF2, i, v1, v2); %#ok<WNTAG>
0073     end
0074 end