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+   VCGLib  http://www.vcglib.net                                         o o     
+   Visual and Computer Graphics Library                            o     o   
+                                                                  _   O  _   
+   Copyright(C) 2005-2006                                           \/)\/    
+   Visual Computing Lab  http://vcg.isti.cnr.it                    /\/|      
+   ISTI - Italian National Research Council                           |      
+                                                                      \      
+   Metro 4.07 2007/05/11 
+   All rights reserved.                                                      
+   
+                                                                       
+This program is free software; you can redistribute it and/or modify      
+it under the terms of the GNU General Public License as published by      
+the Free Software Foundation; either version 2 of the License, or         
+(at your option) any later version.                                       
+                                                                          
+This program is distributed in the hope that it will be useful,           
+but WITHOUT ANY WARRANTY; without even the implied warranty of            
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             
+GNU General Public License (http://www.gnu.org/licenses/gpl.txt)          
+for more details.                                                 
+
+--- Synopsis ---
+
+Metro is a tool designed to evaluate the difference between two triangular meshes. 
+Metro adopts an approximated approach based on surface sampling and point-to-surface distance computation. 
+Please, when using this tool, cite the following reference:
+
+
+P. Cignoni, C. Rocchini and R. Scopigno
+"Metro: measuring error on simplified surfaces"
+Computer Graphics Forum, Blackwell Publishers, vol. 17(2), June 1998, pp 167-174
+
+
+For any question about this software please contact:
+Paolo Cignoni ( paolo.cignoni@isti.cnr.it )
+
+--- General Info ---
+
+Metro is a tool designed to evaluate the difference between two triangular meshes. 
+Metro adopts an approximated approach based on surface sampling and point-to-surface distance computation. 
+Three different surface sampling methods are implemented:
+
+    *   Montecarlo sampling (pick k random samples in the interior of each face)
+    *   Subdivision sampling (recursively subdivide each face along the longest edge and choose the sample in the center of each cell)
+    *   Similar Triangles sampling (subdivide each face F in k polygons similar to F and sample the face in correspondence with the vertices of these polygons, internal to F)
+
+Note that the three methods described above are used to sample only the interior of each face. 
+A different scheme is used to sample vertices and edges: vertices are sampled in the straightforward manner, 
+while edges are sampled by uniformly interleaving samples along each edge.
+
+Three different Spatial indexing structures can be used to find the closest point to a sample, a Statically Allocated Uniform Grid, a Hashed Uniform Grid and a Hierarchy of axis aligned bounding boxes.
+
+--- Basic usage ---
+
+Metro is a command-line tool which allows the user to select among different sampling schemes. 
+A list of the command-line parameters accepted by the tool is shown in the following.
+
+Usage: Metro file1 file2 [opts]
+
+where "file1" and "file2" are the input meshes in PLY, OFF or STL format, and opts can be:
+
+  -v         disable vertex sampling
+  -e         disable edge sampling
+  -f         disable face sampling
+  -u         ignore unreferred vertices
+  -sx        set the face sampling mode
+             where x can be:
+              -s0  montecarlo sampling
+              -s1  subdivision sampling
+              -s2  similar triangles sampling (Default)
+  -n#        set the required number of samples (overrides -A)
+  -a#        set the required number of samples per area unit (overrides -N)
+  -c         save a mesh with error as per-vertex colour and quality
+  -C # #     Set the min/max values used for color mapping
+  -L         Remove duplicated and unreferenced vertices before processing
+  -h         write files with histograms of error distribution
+  -G         Use a static Uniform Grid as Search Structure (default)
+  -A         Use an Axis Aligned Bounding Box Tree as Search Structure
+  -H         Use an Hashed Uniform Grid as Search Structure
+  -O         Use an Octree as Search Structure
+  
+  
+The -C option is useful in combination with -c option for creating a set of 
+meshes with a coherent coloring scheme. 
+It sets how the errors are mapped into color according to the following formula, 
+let e be the error and ColorRamp be a R->RGB function mapping 0..1 values 
+into a smooth RedYellowGreenCyanBlue ramp:
+
+			e=Clamp(e,min,max);
+			VertexColor = ColorRamp( (e-min)/(max-min) );
+
+The Histogram files saved by the -h option contains two column of numbers 
+e_i and p_i; p_i denotes the fraction of the surface having an error 
+between e_i and e_{i+1}. The sum of the second column values should give 1.