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off_util - utilities for OFF files
Usage
Usage: off_util [options] input_files
Read one or more files in OFF format, combine them into a single file and
process it. Most operations manipulate elements, such as adding, deleting,
and combining elements, triangulating and orientimg faces, making an edge
skeleton, and rounding the precision of coordinates. Other miscellaneous
operations include projection onto a sphere, creating a net, truncating
vertices, and converting edges to quadrilaterals. Operations are performeded
in the order they are given on the command line. input_files is the list of
files to process, which may include 'null' as an empty geometry, or if not
given the program reads from standard input.
Options
-h,--help this help message (run 'off_util -H help' for general help)
--version version information
-M <args> Sort and merge elements whose coordinates are the same to
the number of decimal places given by option -l. args is 1 or 2
comma separated parts. The first part is the elements to merge,
which can include: v - vertices, e - edges, f - faces,
a - all (vef), b - bond (merge 've' and delete any face
coincident with another), s - sort without merging.
The second part (default 3) is the merge blend color:
first=1, last=2, rgb=3, ryb=4
-l <lim> minimum distance for unique vertex locations as negative
exponent (default: 12 giving 1e-12)
-O <opt> orient the faces first (if possible) then adjust for signed
volume, value may be: positive, negative, reverse, or flip
(which reverses the orientation of the model as it was input)
-T <rat> truncate vertices by cutting edges at a ratio from each vertex,
can also be 'rat,num' to truncate only vertices of order num
-s skeleton, write the face edges and remove the faces
-t <disp> triangulate, include face parts according to winding number
from: odd, nonzero, positive, negative, triangulate (synonym
for nonzero)
-g geometry only, remove all colours, remove all two-vertex faces
(edges) that are also a face edge
-x <elms> remove OFF face elements. The element string is processed in
order and can include v, e, f to remove OFF faces with one
vertex (vertices), two-vertices (edges) and three or more
vertices (faces), V to remove vertices that are not part
of any face or edge, E to remove two-vertex faces (edges)
that are not part of any face, D to remove two-vertex faces (edges)
that are also a face edge (decorators), F to remove faces that
do not share a vertex with another face
-e Fill in missing explicit edges
-D <list> delete a list of elements, list starts with element letter,
followed by an index number list, given as index ranges separated
by commas. range can be one number or two numbers separated by a
hyphen (default range numbers: 0 and largest index). Element
letters may also be F or E to delete compound parts by part number.
Index number list may be preceded by f, e, v, E or F to find
elements based on connectivity to another element type or part.
Compound parts may also be found by element number. Only elements
specifically specified are deleted. list can have a suffix '%' to
invert results. e or E only act on explicit edges. If some explicit
edges are missing, use -e to fill them in
special connectivity selectors: o - vertices by vertex order
s - faces by number of sides, or to select by a color...
x - vertex color, y - edge color, z - face color
-K <list> keep a list of elements using the same parameters as -D. Only
elements specifically specified are kept along with their vertex
and edge decorators if present. Implicit edges which are kept are
converted to explicit edges
-A <elem> add element, elem is element letter (v, e, f), followed by
element data, optionally followed by ':' and a colour. Data is
v: three comma separated coordinates, 0 for origin
e: a comma separated list of index numbers, joined as a ring
f: a comma separated list of index numbers
negative index numbers are relative to the end of the vertex
list, last vertex is -1 (useful to refer to added vertices.)
-c <col> close polyhedron, each hole converted to a face with colour col,
holes having a vertex with more than two open edges are not filled
-S project onto unit sphere centred at origin
-u <args> unfold a polyhedron into a net, takes up to three comma separated
values for base face index, dihedral fraction (normally 1.0 to
-1.0, default: 0.0 flat), and final option letters: 'f' centre
on centroid of face centres, 'z' align base face normal to z_axis.
-d <dgts> number of significant digits (default 16) or if negative
then the number of digits after the decimal point
-o <file> write output to file (default: write to standard output)
Examplescombine two files/models into a single fileoff_util cube oct > cube_and_oct.off Combine two files/models into a single file, and merge all elements. The first off_util command uses a default average for colouring blended elements, and the second command simply uses the colour from the first of blended elements. off_color -f red cube > red_cube.off off_color -f yellow cube > yellow_cube.off off_util -M a red_cube.off yellow_cube.off | antiview off_util -M a,first red_cube.off yellow_cube.off | antiview Combine two files/models into a single file, and merge coincident vertices only off_util -M v std_cube std_cube | antiview -n vf Add elements to a model off_util -A v0,0,1:blue -A f8,0,2:yellow -A e8,4,6:green cube | antiview Add elements to an empty geometry, to create a model from scratch off_util -A v0,0,1:blue null | poly_kscope -s O | conv_hull | antiview Delete elements from a model. The following commands: delete vertex 0, delete face 1, delete faces 1 and 5, delete faces 1 to 3, delete faces 2 and less and 4 and more (leaving face 3), delete all faces ecept for faces 0 and 1. off_util -D v0 cube | antiview off_util -D f1 cube | antiview off_util -D f1,5 cube | antiview off_util -D f1-3 cube | antiview off_util -D f-2,4- cube | antiview off_util -D f0,1% cube | antiview Delete edge or face parts of a model. The following commands: delete edge part 0, delete face part 0 off_util -D E0 uc4 | antiview off_util -D F0 uc4 | antiview Delete elements from a model which are connected to other elements. The following commands: delete faces connected to vertex 0, face parts to connected to vertex 1, vertices connected to face 3, vertices connected to face part 0 off_util -D fv0 cube | antiview off_util -D Fv1 uc4 | antiview off_util -D vf3 uc4 | antiview off_util -D vF0 uc4 | antiview Use -e to convert implicit edges to explicit edges before a delete to preserve the edges that have all their supporting faces deleted off_util -e -D fv0 cube | antiview pol_recip -a cube | off_util -e -D F0 | antiview Keep elements from a model. -K is not exactly an opposite to -D, as when it keeps elements it also keeps "decorators", considered to be any coloured vertices or edges which lie on kept elements. If it should keep implicit edges, these will be made explicit. The following commands: keep face 0, keep the edges attached to vertex 1, keep the faces attached to vertex 1, keep the edge part attached to vertex 1, keep the face part attached to vertex 1, keep the edges connected to face 1 of a cube (implicit edges converted to explicit edges) off_util -K f0 uc4 | antiview off_util -K ev1 uc4 | antiview off_util -K fv1 uc4 | antiview off_util -K Ev1 uc4 | antiview off_util -K Fv1 uc4 | antiview Keep elements from a model, inverting selection. When using % with -K, the elements that would have been kept are deleted instead. Decorators are kept, except where they are specificed by the option parameter. The following commands: invert keep of edge part 0 (the only thing deleted is the edges of edge part 0, the vertex decorators are retained as they are decorators for remaining faces), invert keep of face part 0 (face part 0 is deleted along with its decorators.) off_util -K E0% uc4 | antiview off_util -K F0% uc4 | antiview Orient the faces a model. The signed volume of the oriented model will be positive. off_util -O p cube | off_report Triangulate a model, any new internal edges and vertices will be coloured invisible off_util -t tri tr_cube | antiview -n f off_util -t tri -g tr_cube | antiview -n f Reduce a model to an uncoloured mesh. Remove any edges or vertices not on faces. Applying this to the previous triangulated model off_util -t tri -g tr_cube | antiview -n f Remove particular elements, e.g. remove edges from the previous skeleton model off_util -s ico -x e | antiview Make an edge skeleton by replacing faces with their surrounding edges off_util -s ico | antiview Close a polyhedron. The first command deletes a cube vertex and closes the opening. The second deletes two non-coplanar adjacent faces and closes the opening with a non-planar face. The third command shows that if a vertex lies on more than one opening those openings cannot be closed. off_util -D v0 -c red cube | antiview off_util -D f0,1 -c none cube | antiview -t no_tri off_util -D f0,2 -c none oct | antiview -t no_tri Truncate all vertices, or all 4-way vertices, to 1/3 along the edges off_util -T 1/3 rd | antiview off_util -T 1/3,4 rd | antiview Project a model onto a unit sphere, the resulting polyhedron may have non-planar faces off_util -S rd | antiview Truncate the number of decimal places for coordinates in the output off_util -d 3 tet Make a net of a polyhedron (very basic) off_util -u 0,0,z ico | antiview NotesDeleting ElementsDelete and keep operations work in slightly different ways.Delete, -D
Keep, -K
Other NotesOption -E is like the join operation in Conway Notation.The face sorting performed by option -M orients faces in a particular way. Option -O will generally reorient some of the sorted faces, and this will always be true if the input is a polyhedron.
The coordinates of a file can be tidied up by running off_util -d
twice, the first time with a negative number to truncate the coordinate
at a number of decimals, the second time with a positive number to
truncate the trailing zeros. For example, to tidy
pol_recip cubo | off_trans -s r
pol_recip cubo | off_trans -s r | off_util -d -1 | off_util -d 1
Next:
planar - convert overlapping coplanar polygons to tiles
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Contact: adrian@antiprism.com - Modified 27.3.2019 |