A minimalistic PLY file reader.

WARNING: This is a simplistic reader that can only handle one kind of
data formatting. The file must be a binary encoded following the
binary_little_endian format, there must be 3 floats per vertex, and 3
integer per face, nothing else. Any variation will result in a crash at
best.

Everything else I could find was super slow.

src/@deproj/deproj.m

@@ -127,6 +127,10 @@ classdef deproj
         
         % Sort x,y coordinates along a continuous contour.
         P2 = find_countour( P )
+
+        % Read a PLY file.
+        [ V, F, comments ] = ply_read( file_path )
+
         
 
     end

src/@deproj/ply_read.m

+function [ V, F, comments ] = ply_read( file_path )
+%% PLY_READ Read a PLY file.
+% WARNING: This is a simplistic reader that can only handle one kind of
+% data formatting. The file must be a binary encoded following the
+% binary_little_endian format, there must be 3 floats per vertex, and 3
+% integer per face, nothing else. Any variation will result in a crash at
+% best.
+
+% ply
+% format binary_little_endian 
+% comment VCGLIB generated -> I did it with MeshLab.
+% element vertex 2607
+% property float x
+% property float y
+% property float z
+% element face 5000
+% property list uchar int vertex_indices
+% end_header
+
+    INT_SIZE        = 8;
+    UCHAR_SIZE      = 1;
+
+    fid = fopen( file_path, 'r' );
+
+    % Check 1st line.
+    first_line = fgetl( fid );
+    if ~strcmpi( first_line, 'ply')
+        error( 'ply_read:NotPLYFile', '%s is not a PLY file.', file_path)
+    end
+
+    current_line = first_line;
+    comments = {};
+    while ~strcmpi( current_line, 'end_header')
+
+        current_line = fgetl( fid );
+
+        if startsWith( current_line, 'comment ', 'IgnoreCase', true )
+            comments = [ comments
+                current_line( numel( 'comment ' ) : end )
+                ]; %#ok<AGROW>
+        end
+
+        if startsWith( current_line, 'element vertex ', 'IgnoreCase', true )
+            n_vertices = str2double( current_line( numel( 'element vertex ' ) : end ) );
+        end
+
+        if startsWith( current_line, 'element face ', 'IgnoreCase', true )
+            n_faces = str2double( current_line( numel( 'element face ' ) : end ) );
+        end
+
+    end
+
+    vertex_record_length = 3;
+    V = fread( fid, vertex_record_length * n_vertices, 'single' );
+    V = reshape( V, [ vertex_record_length n_vertices ] )';
+
+    face_record_length = 3;
+    % Read the whole block as bytes, that we will decode later.
+    block = fread( fid, ( 3 * INT_SIZE + UCHAR_SIZE ) * n_faces, '*uint8' );
+
+    F = zeros( n_faces, face_record_length, 'int32' );
+    index = 1;
+    for i = 1 : n_faces
+
+        index = index + 1;
+        [ val, index ] = read_int( block, index );
+        F( i , 1 ) = 1 + val;
+        [ val, index ] = read_int( block, index );
+        F( i , 2 ) = 1 + val;
+        [ val, index ] = read_int( block, index );
+        F( i , 3 ) = 1 + val;
+    end
+
+
+    fclose( fid );
+    
+    
+    function [ val, index ] = read_int( block, index )
+        val = typecast( block( index : index + 3 ), 'int32' );
+        index = index + 4;
+    end
+
+end
\ No newline at end of file