.. highlightlang:: us

.. _poly_poly_clip:

poly_poly_clip
==============

.. index:: poly_poly_clip

.. us.tag  poly_poly_clip NOTREADYENGLISH base_graph New363

:ref:`poly_poly_clip` calculates the intersections between a polygon (open polygon)
and a data hull (closed polygon).

.. function::  <rmXY, idx> = poly_poly_clip(nOpt, clip, poly)

.. us.return

**Return Value**

*rmXY*, *idx*: *rmXY* is a matrix with two columns. The first column
contains the x-coordinates and the second column the y-coordinates of the result
polygon. *idx* is an index vector with the end points of the polygons 
(see example).

.. us.params

**Parameters**

.. uparam:: nOpt

   *nOpt* specifies what result should be computed. *nOpt* can be one of the
   following values:

.. list-table::
   :header-rows: 1

   * - Value
     - Meaning
   * - 0
     - union (hull containing both polygons).
   * - 1
     - difference (part of the subject polygon that is inside the clip hull).
   * - 2
     - difference (part of the subject polygon that is inside the clip hull).
   * - 3
     - hull without subject polygon.

.. uparam:: clip

   *clip* are the x/y-coordinates of the clip polygon. The coordinates must
   be given as a complex vector (x + 1i*y) (see example).

.. uparam:: poly

   *poly* are the x/y-coordinates of the subject polygon. The coordinates must
   be given as a complex vector (x + 1i*y) (see example).

.. us.example

**Example**

.. image:: S:/uniplot-obj/images/poly_poly_clip.*

::

   def test(option)
   {
       xhull = [1, 1, 2, 2, 1];
       yhull = [1, 2, 2, 1, 1];
       nh = len(xhull)
       h = plot(xhull,yhull)
       xp = [1.3, 1.3, 1.6, 1.6, 1.3];
       yp = [0.3, 2.6, 2.6, 0.3, 0.3];    
       <xy, idx> = poly_poly_clip(option, xhull[1:nh] + 1i * yhull[1:nh], xp + 1i*yp);
       if (len(idx) == 1 && idx[1] == 0) {
           return TRUE;
       }
       nPoly = len(idx);
       if (len(xy) > 1) {
           idx = [0;idx];
           for (i in 2:nPoly+1) {
               h = plot(xy[idx[i-1]+1:idx[i]; 1], xy[idx[i-1]+1:idx[i];2], h[2]);
           }
       }
       return xy;
   }

.. seealso::
   :ref:`poly_line_clip`,
   :ref:`poly_hull`

:sub:`id-1848134`