removeUnreferencedVertices

REMOVEUNREFERENCEDVERTICES Remove unreferenced vertices of a mesh.

   [V2, F2] = removeUnreferencedVertices(V, F)
   Remove unreferenced/unindexed vertices of a mesh defined by the
   vertices V and faces F.

   [VIDX, FIDX] = removeUnreferencedVertices(V, F, 'indexOutput', true)
   Gives the indices instead of the final mesh. This means:
       V2 = V(VIDX,:)
       F2 = FIDX(F)

   Example:
     [v, f] = createCube;
     % Add unreferenced vertices
     for idx = [2, 5, 7]
         v = [v(1:idx,:); rand(1,3); v(idx+1:end,:)];
         f(find(f>idx))=f(find(f>idx))+1; %#ok<FNDSB> 
     end
     [v2, f2] = removeUnreferencedVertices(v, f);

   See also
     trimMesh, removeDuplicateFaces, removeDuplicateVertices

   Source
     remove_unreferenced.m by Alec Jacobson:
       https://github.com/alecjacobson/gptoolbox

0001 function varargout = removeUnreferencedVertices(v, varargin)
0002 %REMOVEUNREFERENCEDVERTICES Remove unreferenced vertices of a mesh.
0003 %
0004 %   [V2, F2] = removeUnreferencedVertices(V, F)
0005 %   Remove unreferenced/unindexed vertices of a mesh defined by the
0006 %   vertices V and faces F.
0007 %
0008 %   [VIDX, FIDX] = removeUnreferencedVertices(V, F, 'indexOutput', true)
0009 %   Gives the indices instead of the final mesh. This means:
0010 %       V2 = V(VIDX,:)
0011 %       F2 = FIDX(F)
0012 %
0013 %   Example:
0014 %     [v, f] = createCube;
0015 %     % Add unreferenced vertices
0016 %     for idx = [2, 5, 7]
0017 %         v = [v(1:idx,:); rand(1,3); v(idx+1:end,:)];
0018 %         f(find(f>idx))=f(find(f>idx))+1; %#ok<FNDSB>
0019 %     end
0020 %     [v2, f2] = removeUnreferencedVertices(v, f);
0021 %
0022 %   See also
0023 %     trimMesh, removeDuplicateFaces, removeDuplicateVertices
0024 %
0025 %   Source
0026 %     remove_unreferenced.m by Alec Jacobson:
0027 %       https://github.com/alecjacobson/gptoolbox
0028 
0029 % ------
0030 % Author: oqilipo
0031 % E-mail: N/A
0032 % Created: 2023-07-14, using Matlab 9.13.0.2080170 (R2022b) Update 1
0033 % Copyright 2023-2024
0034 
0035 %% Parse input
0036 if isstruct(v)
0037     [v, f] = parseMeshData(v);
0038 else
0039     f = varargin{1};
0040     varargin(1) = [];
0041 end
0042 
0043 parser = inputParser;
0044 logParValidFunc = @(x) (islogical(x) || isequal(x,1) || isequal(x,0));
0045 addParameter(parser, 'indexOutput', false, logParValidFunc);
0046 parse(parser, varargin{:});
0047 indexOutput = parser.Results.indexOutput;
0048 
0049 %% Remove unreferenced/unindexed vertices
0050 if isempty(f)
0051     [vIdx, fIdx] = deal([]);
0052 else
0053     % Get list of unique vertex indices that occur in faces
0054     sF = sort(f(:));
0055     I = [true;diff(sF)~=0];
0056     U = sF(I);
0057     % Get list of vertices that do not occur in faces
0058     n = size(v,1);
0059     NU = find(0==sparse(U,1,1,n,1));
0060     % assert((size(U,1) + size(NU,1)) == n);
0061     % Allocate space for an indexmap
0062     fIdx = zeros(n,1);
0063     % Reindex vertices that occur in faces to be first
0064     fIdx(U) = 1:size(U,1);
0065     % Reindex vertices that do not occur in faces to come after those that do
0066     fIdx(NU) = size(U,1) + (1:size(NU,1));
0067     % New vertices
0068     vIdx = ismember(1:length(v),U);
0069     % v2(fIdx,:) = v;
0070     % v2 = v2(1:max(fIdx(f(:))),:);
0071 end
0072 
0073 %% Parse output
0074 if indexOutput
0075     % If indices are requested
0076     varargout = {vIdx, fIdx};
0077 else
0078     v2 = v(vIdx,:);
0079     f2 = fIdx(f);
0080     varargout = formatMeshOutput(nargout, v2, f2);
0081 end
0082 
0083 end