[ новости /+++ | форум | теги | ]

NAME
     clip - Clip an OOGL object against planes or other surfaces

SYNOPSIS
     clip [-v axisx,y,z,...]
         [-g value-or-point] [-l value-or-point]
         [-s nstrips[,fraction]] [-e]
         [-sph centerx,y,z,...] [-cyl centerx,y,z,...]
         [ooglfile]

DESCRIPTION
     Clip, adapted from Daeron Meyer's ginsu module, allows clip-
     ping  an  OOGL  object against planes, spheres, or cylinders
     from the UNIX command line.  Its input can come from a  file
     or standard input; output is written to standard output.

     Options specify a function of space position; the output  is
     the  portion  of the object where the function is greater or
     less than some given value, or the portion lying between two
     values.    Alternatively,  an  object  can  be  sliced  into
     equally-spaced strips.  Objects may be of any dimension (but
     see the BUGS section).

     Options are:

     -g value-or-point

     -l value-or-point
          Select the portion of the object where the function  is
          greater  than  (-g)  or less than (-l) the given value.
          If both are specified, the result is the portion of the
          object satisfying both conditions.

          If, rather than a single number, the argument to -l  or
          -g  is  a point (a series of x,y,z,... values separated
          by commas, with no embedded blanks), then the  clipping
          surface is one chosen to pass through that point.

     -v axisx,y,z,...
          Specifies a direction in space.   For  planar  clipping
          (the  default),  it's  the  plane normal direction; the
          clipping function is  the  inner  product  between  the
          direction  vector  and  the  point  on the object.  For
          cylindrical clipping, -v specifies the direction of the
          cylinder's  axis; the clipping function is the distance
          from the axis.

     -sph centerx,y,z,...
          Clip against spheres centered on x,y,z,....  The  clip-
          ping  function  is  the distance from the given center.
          Coordinates must be separated by commas without  inter-
          vening spaces.

     -cyl centerx,y,z,...
          Clip against cylinders with  an  axis  passing  through
          centerx,y,z,...,  with  axis  direction given by the -v
          option.  The clipping function is the distance from the
          axis.

     -s nslices[,fraction]
          Clip an object into a series of nslices  ribbons  span-
          ning  its entire extent -- the range of function-values
          over the object.  Part of each ribbon is  omitted;  the
          fraction,  default  .5,  sets  the width of the visible
          part of a ribbon compared to the ribbon period.   There
          are  a  total  of  (nslices+fraction-1)  ribbon periods
          across the object, so e.g. -s 2,.5  slices  the  object
          into equal thirds, omitting the middle third.  The out-
          put OOGL object is a LIST of OFFs, one per ribbon.

     -e   Don't emit  a  clipped  OOGL  object,  just  print  two
          numbers,  listing  the  minimum  and  maximum  function
          values for the object.  If -g or  -l  clipping  options
          are specified, the object is clipped before determining
          the function range.  If none  of  the  object  remains,
          clip prints "0 0".

EXAMPLES
     To extract the portion of an object lying below the  x+y+z=1
     plane:

       clip -l 1  -v 1,1,1  file.oogl  > portion.oogl

     To extract the portion of an object lying  in  the  positive
     octant  and  below  the  x+y+z=1 plane, we can pipe multiple
     instances of clip  together  to  find  the  intersection  of
     several half-spaces:

       clip -g 0  -v 1,0,0 file.oogl | \
          clip -g 0 -v 0,1,0 | \
          clip -g 0 -v 0,0,1 | \
          clip -l 1 -v 1,1,1 > portion.oogl

     To find the region lying between two surfaces (either  above
     one  and  below  the other, or below the first and above the
     second), say the planes 2x + y -.5z = 1 and y + 2z = 0:

          echo "{ LIST"
          clip -v 2,1,-.5 -g 1  file.oogl | clip -v 0,1,2 -l 0
          clip -v 2,1,-.5 -l 1  file.oogl | clip -v 0,1,2 -g 0
          echo "}"

     We use pipelines to compute intersections,  and  a  LIST  to
     form their union.

SEE ALSO
     ginsu(1)

BUGS
     Uses anytooff(1) to convert input data to OFF format  inter-
     nally;  this  can  lose  information.   The  only arbitrary-
     dimensional form accepted at present is nOFF, not  nSKEL  or
     nMESH.   However  the  four-dimensional  4OFF, 4QUAD, 4MESH,
     4VECT, etc. formats should work.

     Clip really only clips edges.  If a curved clipping  surface
     cuts  an  edge twice, or removes only an interior portion of
     some polygon, clip misses it entirely.  Clipping  against  a
     curved  surface yields a straight edge (a chord of the ideal
     curved edge segment).  This latter failing  might  be  fixed
     someday.

Партнёры:

Хостинг: