removeMeshFaces

REMOVEMESHFACES Remove faces from a mesh by face indices.
   [V2, F2] = removeMeshFaces(V, F, FI) removes faces from the mesh by
   the face indices FI into faces F of the mesh. The mesh is represented 
   by the vertex array V and the face array F. The result is the new set 
   of vertices V2 and faces F2 without the faces indexed by FI. FI can be
   either a linear or a logical index.

   [V2, F2] = removeMeshFaces(MESH, FI) with the struct MESH containing 
   the fields "vertices" (V) and "faces" (F)
   
   MESH2 = removeMeshFaces(V, F, FI) with the struct MESH2 containing the
   fields "vertices" (V2) and "faces" (F2)
   
   MESH2 = removeMeshFaces(MESH, FI) with the structs MESH and MESH2 
   containing the fields "vertices" (V, V2) and "faces" (F, F2)
   
   Example
     [v, f] = createSoccerBall;
     f = triangulateFaces(f);
     fI = true(length(f),1);
     fI(1:length(f)/2) = false;
     [v2, f2] = removeMeshFaces(v, f, fI);
     drawMesh(v, f, 'faceColor', 'none', 'faceAlpha', .2);
     drawMesh(v2, f2, 'faceAlpha', .7);
     view(3); axis equal
   
   See also
   meshes3d, drawMesh

 ---------
 Authors: oqilipo, David Legland
 Created: 2017-07-04

0001 function varargout = removeMeshFaces(v, f, fI)
0002 %REMOVEMESHFACES Remove faces from a mesh by face indices.
0003 %   [V2, F2] = removeMeshFaces(V, F, FI) removes faces from the mesh by
0004 %   the face indices FI into faces F of the mesh. The mesh is represented
0005 %   by the vertex array V and the face array F. The result is the new set
0006 %   of vertices V2 and faces F2 without the faces indexed by FI. FI can be
0007 %   either a linear or a logical index.
0008 %
0009 %   [V2, F2] = removeMeshFaces(MESH, FI) with the struct MESH containing
0010 %   the fields "vertices" (V) and "faces" (F)
0011 %
0012 %   MESH2 = removeMeshFaces(V, F, FI) with the struct MESH2 containing the
0013 %   fields "vertices" (V2) and "faces" (F2)
0014 %
0015 %   MESH2 = removeMeshFaces(MESH, FI) with the structs MESH and MESH2
0016 %   containing the fields "vertices" (V, V2) and "faces" (F, F2)
0017 %
0018 %   Example
0019 %     [v, f] = createSoccerBall;
0020 %     f = triangulateFaces(f);
0021 %     fI = true(length(f),1);
0022 %     fI(1:length(f)/2) = false;
0023 %     [v2, f2] = removeMeshFaces(v, f, fI);
0024 %     drawMesh(v, f, 'faceColor', 'none', 'faceAlpha', .2);
0025 %     drawMesh(v2, f2, 'faceAlpha', .7);
0026 %     view(3); axis equal
0027 %
0028 %   See also
0029 %   meshes3d, drawMesh
0030 %
0031 % ---------
0032 % Authors: oqilipo, David Legland
0033 % Created: 2017-07-04
0034 
0035 % parse inputs
0036 narginchk(2,3)
0037 nargoutchk(1,2)
0038 
0039 if nargin == 2
0040     fI = f;
0041     [v, f] = parseMeshData(v);
0042 end
0043 
0044 p = inputParser;
0045 isIndexToFaces = @(x) ...
0046     (islogical(x) && isequal(length(x), size(f,1))) || ...
0047     (all(floor(x)==x) && min(x)>=1 && max(x)<=size(f,1));
0048 addRequired(p,'fI',isIndexToFaces)
0049 parse(p, fI);
0050 if ~islogical(p.Results.fI)
0051     fI=false(size(f,1),1);
0052     fI(p.Results.fI)=true;
0053 else
0054     fI=p.Results.fI;
0055 end
0056     
0057 
0058 % algorithm
0059 f2 = f(~fI,:);
0060 [unqVertIds, ~, newVertIndices] = unique(f2);
0061 v2 = v(unqVertIds,:);
0062 f2 = reshape(newVertIndices,size(f2));
0063 
0064 
0065 % parse outputs
0066 if nargout == 1
0067     mesh2.vertices=v2;
0068     mesh2.faces=f2;
0069     varargout{1}=mesh2;
0070 else
0071     varargout{1}=v2;
0072     varargout{2}=f2;
0073 end
0074 
0075 end