trimMesh

TRIMMESH Reduce memory footprint of a polygonal mesh.

   [V2, F2] = trimMesh(V, F)
   Unreferenced vertices are removed.
   Following functions are implemented only for numeric faces:
       Duplicate vertices are removed.
       Duplicate faces are removed.

   Example
     [V, F] = createIcosahedron;
     F(13:20, :) = [];
     [V2, F2] = trimMesh(V, F);
     figure; drawMesh(V2, F2)
     view(3); axis equal;
     axis([-1 1 -1 1 0 2])

   See also
     meshes3d, clipMeshVertices

0001 function varargout = trimMesh(varargin)
0002 %TRIMMESH Reduce memory footprint of a polygonal mesh.
0003 %
0004 %   [V2, F2] = trimMesh(V, F)
0005 %   Unreferenced vertices are removed.
0006 %   Following functions are implemented only for numeric faces:
0007 %       Duplicate vertices are removed.
0008 %       Duplicate faces are removed.
0009 %
0010 %   Example
0011 %     [V, F] = createIcosahedron;
0012 %     F(13:20, :) = [];
0013 %     [V2, F2] = trimMesh(V, F);
0014 %     figure; drawMesh(V2, F2)
0015 %     view(3); axis equal;
0016 %     axis([-1 1 -1 1 0 2])
0017 %
0018 %   See also
0019 %     meshes3d, clipMeshVertices
0020 
0021 % ------
0022 % Author: David Legland, oqilipo
0023 % E-mail: david.legland@inrae.fr
0024 % Created: 2014-08-01, using Matlab 8.3.0.532 (R2014a)
0025 % Copyright 2014-2024 INRA - Cepia Software Platform
0026 
0027 % parse input data
0028 [vertices, faces] = parseMeshData(varargin{:});
0029 
0030 if isnumeric(faces)
0031     % Process meshes with faces given as Nf-by-3 or Nf-by-4 numeric arrays
0032 
0033     % Delete duplicate vertices
0034     [tempVertices, tempFaces] = removeDuplicateVertices(vertices, faces);
0035     % Delete unindexed/unreferenced vertices
0036     [tempVertices2, tempFaces2] = removeUnreferencedVertices(tempVertices, tempFaces);
0037     % Delete duplicate faces
0038     [~, uniqueFaceIdx, ~] = unique(tempFaces2, 'rows');
0039     duplicateFaceIdx = ~ismember(1:size(tempFaces2,1), uniqueFaceIdx);
0040     [vertices2, faces2] = removeMeshFaces(tempVertices2, tempFaces2, duplicateFaceIdx);
0041 
0042 elseif iscell(faces)
0043     % Process meshes with faces given as cell array of row vectors
0044 
0045     nVertices = size(vertices, 1);
0046     nFaces = length(faces);
0047 
0048     % identify vertices referenced by at least one face
0049     vertexUsed = false(nVertices, 1);
0050     for iFace = 1:nFaces
0051         face = faces{iFace};
0052         vertexUsed(face) = true;
0053     end
0054     vertices2 = vertices(vertexUsed, :);
0055 
0056     % compute map from old index to new index
0057     inds = find(vertexUsed);
0058     newInds = zeros(nVertices, 1);
0059     for iIndex = 1:length(inds)
0060         newInds(inds(iIndex)) = iIndex;
0061     end
0062     
0063     % change labels of vertices referenced by faces
0064     faces2 = cell(1, nFaces);
0065     for iFace = 1:nFaces
0066         faces2{iFace} = newInds(faces{iFace})';
0067     end
0068     
0069 else
0070     error('matGeom:trimMesh', ...
0071         'Unsupported representation for mesh faces');
0072 end
0073 
0074 % format output arguments
0075 varargout = formatMeshOutput(nargout, vertices2, faces2);