Improved a lot!
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Visual Computing Lab http://vcg.isti.cnr.it /\/|
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ISTI - Italian National Research Council |
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Metro 4.05 04/05/2005
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TriDecimator 1.00 2/10/2005
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All rights reserved.
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@ -24,59 +24,53 @@ for more details.
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--- Synopsis ---
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Metro is a tool designed to evaluate the difference between two triangular meshes.
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Metro adopts an approximated approach based on surface sampling and point-to-surface distance computation.
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Please, when using this tool, cite the following reference:
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tridecimator fileIn fileOut face_num [opt]\
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Where opt can be:\
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-e# QuadricError threshold (range [0,inf) default inf)
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-b# Boundary Weight (default .5)
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-q# Quality threshold (range [0.0, 0.866], default .3 )
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-n# Normal threshold (degree range [0,180] default 90)
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-E# Minimal admitted quadric value (default 1e-15, must be >0)
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-Q[y|n] Use or not Quality Threshold (default yes)
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-N[y|n] Use or not Normal Threshold (default no)
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-A[y|n] Use or not Area Weighted Quadrics (default yes)
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-O[y|n] Use or not vertex optimal placement (default yes)
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-S[y|n] Use or not Scale Independent quadric measure(default yes)
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-B[y|n] Preserve or not mesh boundary (default no)
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-T[y|n] Preserve or not Topology (default no)
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-H[y|n] Use or not Safe Heap Update (default no)
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-P Before simplification, remove duplicate & unreferenced vertices
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Supported formats: PLY, OFF, STL
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P. Cignoni, C. Rocchini and R. Scopigno
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"Metro: measuring error on simplified surfaces"
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Computer Graphics Forum, Blackwell Publishers, vol. 17(2), June 1998, pp 167-174
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Available at http://vcg.sf.net
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-- Some technical notes --
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This simplification tool employ a quadric error based edge collapse iterative approach.
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Each possible collapse is scored taking into account
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- its quadric error
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- its quadric boundary error
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- the normal variation caused by the collapse itself
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- the future quality (aspect ratio) of the triangles involved in the collapse
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The simplification can ends when the desired number of triangles has been reached.
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The 'Safe Heap Update' change the set of edges re-inserted in the heap
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after a collapse resulting in a vertex v; this option put back in the
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heap not only incident in the vbut all the edges of the triangles incident
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in v. It slows down a lot.
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The 'Scale Independent quadric' is useful when you want simplify
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two different meshes at the same 'error'; otherwise the quadric
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error used in the heap is somewhat normalized and independent
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of the size of the mesh.
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The Normal threshold avoid to make large changes in variation of the normal
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of the surfaces, but on the other hand it prevent the removal of small 'folded'
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triangles that can be already present. Therefore in most cases is not very useful.
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Cleaning the mesh is mandatory for some input format like STL that always
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duplicates all the vertices.
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You can find some sample mesh to test in the 'Metro Sample dataset' package downloadable from sourceforge.
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For any question about this software please contact:
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Paolo Cignoni ( p.cignoni@isti.cnr.it )
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--- General Info ---
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Metro is a tool designed to evaluate the difference between two triangular meshes.
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Metro adopts an approximated approach based on surface sampling and point-to-surface distance computation.
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Three different surface sampling methods are implemented:
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* Montecarlo sampling (pick k random samples in the interior of each face)
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* Subdivision sampling (recursively subdivide each face along the longest edge and choose the sample in the center of each cell)
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* 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)
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Note that the three methods described above are used to sample only the interior of each face.
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A different scheme is used to sample vertices and edges: vertices are sampled in the straightforward manner,
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while edges are sampled by uniformly interleaving samples along each edge.
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--- Basic usage ---
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Metro is a command-line tool which allows the user to select among different sampling schemes.
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A list of the command-line parameters accepted by the tool is shown in the following.
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Usage: Metro file1 file2 [opts]
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where "file1" and "file2" are the input meshes in PLY, OFF or STL format, and opts can be:
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-v disable vertex sampling
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-e disable edge sampling
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-f disable face sampling
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-u does not ignore unreferred vertices and sample also unreferenced vertices
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(useful for sampling point clouds against meshes)
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-sx set the face sampling mode
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where x can be:
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-S0 montecarlo sampling
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-S1 subdivision sampling
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-S2 similar triangles sampling (Default)
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-n# set the required number of samples (overrides -a)
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-a# set the required number of samples per area unit (overrides -n)
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-c save computed error as vertex colour and quality in two ply files
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-C # # Set the min/max values used for color mapping (useful for taking snapshot with coherent color ramp)
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-L Remove duplicated and unreferenced vertices before processing to avoid
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-H write files with histograms of error distribution
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