.TH POLYMERGE 1gv "25 July 1993" "Geometry Center"
.SH NAME
polymerge \- merge coincident vertices, collinear edges, coplanar faces 
in an OOGL OFF object
.SH SYNOPSIS
\fBpolymerge\fP [\fB\-v\fP \fIvertex_thresh\fP] [\fB\-e\fP \fIedge_thresh\fP]
[\fB\-f\fP \fIface_thresh\fP] [\fB\-V\fP] [\fB\-E\fP] [\fB\-F\fP]
[\fB\-d\fP] [\fB\-b\fP] [\fIinputfile.off\fP]
.SH DESCRIPTION
\fIPolymerge\fP 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:
.IP "\fB\-v\fP \fIvertex_thresh\fP"
Merge vertices when they're closer than \fIvertex_thresh\fP apart;
the default is .00001.
.IP "\fB\-V\fP"
Don't attempt to merge vertices.
.IP "\fB\-e\fP \fIedge_thresh\fP"
Merge edges where |sin(vertex_angle)| < \fIedge_thresh\fP; the default is
.01, merging edges with angles within about .5 degree of 0 or 180 degrees.
When edges are merged, the corresponding vertex is removed.
.IP "\fB\-E\fP"
Don't attempt to merge edges.  (4OFF edges are never merged.)
.IP "\fB\-f\fP \fIface_thresh\fP"
Merge faces sharing an edge where the faces are nearly coplanar: when
|sin(angle_between_face_normal_vectors)| < \fIface_thresh\fP.
The default is .03, or about two degrees.  Note that merging
can create faces which are concave polygons.
.IP "\fB\-F\fP"
Don't attempt to merge faces. (4OFF faces are never merged.)
.IP "\fB\-b\fP"
Produce an output file in .fe format for Brakke's Surface Evolver,
instead of a new OFF file.
.IP "\fB\-d\fP"
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:
.IP "# Vtx \fInnn\fP->\fImmm\fP"
Merged vertices \fInnn\fP and \fImmm\fP (both indices in the original object).
.IP "# Merged face \fInnn\fP into \fImmm\fP (vertices \fIvvv\fP \fIwww\fP) n1.n2 \fIs\fP"
Faces \fInnn\fP and \fImmm\fP in the original object were merged;
their common edge joined original vertices \fIvvv\fP and \fIwww\fP.
The cosine of the angle between the face normals was \fIs\fP.
.IP "\fIvertex coordinates\fP  # \fInewvertno\fP [\fIorder\fP] # \fIoldvertno\fP"
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).
.IP "\fIface description\fP  # \fIoldvertno ...\fP"
For each new face, with \fIN\fP vertices after reduction,
the comment indicates \fIN\fP corresponding vertices in the original object.
.SH AUTHOR
Stuart Levy, Geometry Center, University of Minnesota
.SH "SEE ALSO"
anytooff(1), offconsol(1)
.SH 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.