NAME

       PDL::Graphics::TriD::Contours - 3D Surface contours for TriD

SYNOPSIS

           # A simple contour plot in black and white

           use PDL::Graphics::TriD;
           use PDL::Graphics::TriD::Contours;
           $size = 25;
           $x = (xvals zeroes $size,$size) / $size;
           $y = (yvals zeroes $size,$size) / $size;
           $z = (sin($x*6.3) * sin($y*6.3)) ** 3;
           $data=new PDL::Graphics::TriD::Contours($z,
                      [$z->xvals/$size,$z->yvals/$size,0]);
           PDL::Graphics::TriD::graph_object($data)

FUNCTIONS

   new()
       Define a new contour plot for TriD.

         $data=new PDL::Graphics::TriD::Contours($d,[$x,$y,$z],[$r,$g,$b],$options);

       where $d is a 2D pdl of data to be contoured. [$x,$y,$z] define a 3D map of $d into the
       visualization space [$r,$g,$b] is an optional [3,1] piddle specifying the contour color
       and $options is a hash reference to a list of options documented below.  Contours can also
       be colored by value using the set_color_table function.

         ContourInt  => 0.7  # explicitly set a contour interval
         ContourMin  => 0.0  # explicitly set a contour minimum
         ContourMax  => 10.0 # explicitly set a contour maximum
         ContourVals => $pdl # explicitly set all contour values
         Label => [1,5,$myfont] # see addlabels below
         Font =>  $font      # explicitly set the font for contour labels

         If ContourVals is specified ContourInt, ContourMin, and ContourMax
         are ignored.  If no options are specified, the algorthym tries to
         choose values based on the data supplied.  Font can also be specified or
         overwritten by the addlabels() function below.

   addlabels()
       Add labels to a contour plot

         $contour->addlabels($labelint,$segint,$font);

       $labelint is the integer interval between labeled contours.  If you have 8 contour levels
       and specify $labelint=3 addlabels will attempt to label the 1st, 4th, and 7th contours.
       $labelint defaults to 1.

       $segint specifies the density of labels on a single contour level.  Each contour level
       consists of a number of connected line segments, $segint defines how many of these
       segments get labels.  $segint defaults to 5, that is every fifth line segment will be
       labeled.

   set_colortable($table)
       Sets contour level colors based on the color table.

       $table is passed in as either a piddle of [3,n] colors, where n is the number of contour
       levels, or as a reference to a function which expects the number of contour levels as an
       argument and returns a [3,n] piddle.  It should be straight forward to use the
       PDL::Graphics::LUT tables in a function which subsets the 256 colors supplied by the look
       up table into the number of colors needed by Contours.

   coldhot_colortable()
       A simple colortable function for use with the set_colortable function.

       coldhot_colortable defines a blue red spectrum of colors where the smallest contour value
       is blue, the highest is red and the others are shades in between.