NAME

       polymerge  -  merge  coincident  vertices,  collinear edges, coplanar faces in an OOGL OFF
       object

SYNOPSIS

       polymerge [-v vertex_thresh] [-e edge_thresh] [-f face_thresh] [-V] [-E]  [-F]  [-d]  [-b]
       [inputfile.off]

DESCRIPTION

       Polymerge eliminates redundancies from polyhedral objects in OOGL's OFF format, and writes
       another OFF object to its standard output.  (Optionally it can produce  instead  an  input
       file for Brakke's Evolver.)  Specifically, it combines nearly-coincident vertices, nearly-
       collinear edges, and nearly-coplanar faces.  Vertices which aren't used on  any  face  are
       deleted,  as are faces with less than three vertices.  Thresholds for approximate equality
       are adjustable from the command line.  Options are:

       -v vertex_thresh
              Merge vertices when they're closer than vertex_thresh apart; the default is .00001.

       -V     Don't attempt to merge vertices.

       -e edge_thresh
              Merge edges where |sin(vertex_angle)| < edge_thresh; the default is When edges  are
              merged, the corresponding vertex is removed.

       -E     Don't attempt to merge edges.  (4OFF edges are never merged.)

       -f face_thresh
              Merge   faces   sharing   an  edge  where  the  faces  are  nearly  coplanar:  when
              |sin(angle_between_face_normal_vectors)| < face_thresh.  The  default  is  .03,  or
              about two degrees.  Note that merging can create faces which are concave polygons.

       -F     Don't attempt to merge faces. (4OFF faces are never merged.)

       -b     Produce an output file in .fe format for Brakke's Surface Evolver, instead of a new
              OFF file.

       -d     Include debugging information as comments in the  new  OFF  object.   The  comments
              indicate which vertices and faces in the original object correspond to which in the
              new one.  Messages include:

       # Vtx nnn->mmm
              Merged vertices nnn and mmm (both indices in the original object).

       # Merged face nnn into mmm (vertices vvv www) n1.n2 s
              Faces nnn and mmm in the original object were  merged;  their  common  edge  joined
              original  vertices  vvv  and www.  The cosine of the angle between the face normals
              was s.

       vertex coordinates  # newvertno [order] # oldvertno
              Each vertex written appears with its new index, its order (number of edges touching
              that  vertex),  and  its old index (index of a corresponding vertex in the original
              object).

       face description  # oldvertno ...
              For each new face, with  N  vertices  after  reduction,  the  comment  indicates  N
              corresponding vertices in the original object.

AUTHOR

       Stuart Levy, Geometry Center, University of Minnesota

SEE ALSO

       anytooff(1), offconsol(1)

BUGS

       Coplanar  faces are merged even if they were assigned different colors.  Should be able to
       handle binary OFF objects, but this hasn't been tested.