=head1 NAME

Math::Polygon::Surface - Polygon with exclusions

=head1 SYNOPSIS

 my $outer   = Math::Polygon->new( [1,2], [2,4], [5,7], [1,2] );
 my $surface = Math::Polygon::Surface->new($outer);

=head1 DESCRIPTION

A surface is one polygon which represents the outer bounds of an
array, plus optionally a list of polygons which represent exclusions
from that outer polygon.

=head1 METHODS

=head2 Constructors

=over 4

=item $obj-E<gt>B<new>([OPTIONS], [POLYGONS], [OPTIONS])

=item Math::Polygon::Surface-E<gt>B<new>([OPTIONS], [POLYGONS], [OPTIONS])

You may add OPTIONS after and/or before the POLYGONS.  You may also use
the "outer" and "inner" options.  POLYGONS are references to ARRAYs of points,
each an ARRAY of X and Y, but better instantiated L<Math::Polygon|Math::Polygon> objects.

 -Option--Default
  inner   []
  outer   undef

=over 2

=item inner => ARRAY-OF-POLYGONS

The inner polygons, zero or more L<Math::Polygon|Math::Polygon> objects.

=item outer => POLYGON

The outer polygon, a L<Math::Polygon|Math::Polygon>.

=back

=back

=head2 Attributes

=over 4

=item $obj-E<gt>B<inner>

Returns a list (often empty) of inner polygons.

=item $obj-E<gt>B<outer>

Returns the outer polygon.

=back

=head2 Simple calculations

=over 4

=item B<area>

Returns the area enclosed by the outer polygon, minus the areas of the
inner polygons.
See method L<Math::Polygon::area()|Math::Polygon/"Geometry">.

=item $obj-E<gt>B<bbox>

Returns a list with four elements: (xmin, ymin, xmax, ymax), which describe
the bounding box of the surface, which is the bbox of the outer polygon.
See method L<Math::Polygon::bbox()|Math::Polygon/"Geometry">.

=item $obj-E<gt>B<perimeter>

The length of the border: sums outer and inner perimeters.
See method L<Math::Polygon::perimeter()|Math::Polygon/"Geometry">.

=back

=head2 Clipping

=over 4

=item $obj-E<gt>B<fillClip1>(BOX)

Clipping a polygon into rectangles can be done in various ways.
With this algorithm, the parts of the polygon which are outside
the BOX are mapped on the borders.

All polygons are treated separately.

=item $obj-E<gt>B<lineClip>(BOX)

Returned is a list of ARRAYS-OF-POINTS containing line pieces
from the input surface.  Lines from outer and inner polygons are
undistinguishable.
See method L<Math::Polygon::lineClip()|Math::Polygon/"Clipping">.

=item $obj-E<gt>B<string>

Translate the surface structure into some string.  Use Geo::WKT if you
need a standardized format.

Returned is a single string possibly containing multiple lines.  The first
line is the outer, the other lines represent the inner polygons.

=back

=head1 DIAGNOSTICS

=over 4

=item Error: surface requires outer polygon

=back

=head1 SEE ALSO

This module is part of Math-Polygon distribution version 1.02,
built on September 19, 2011. Website: F<http://perl.overmeer.net/geo/>

=head1 LICENSE

Copyrights 2004,2006-2011 by Mark Overmeer. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://www.perl.com/perl/misc/Artistic.html>

