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.\" ========================================================================
.\"
.IX Title "TriD::Contours 3pm"
.TH TriD::Contours 3pm "2023-06-17" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
PDL::Graphics::TriD::Contours \- 3D Surface contours for TriD
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    # 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;
\&    $data=PDL::Graphics::TriD::Contours\->new($z,
\&               [$z\->xvals/$size,$z\->yvals/$size,0]);
\&    PDL::Graphics::TriD::graph_object($data)
.Ve
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "\fBnew()\fP"
.IX Subsection "new()"
Define a new contour plot for TriD.
.PP
.Vb 1
\&  $data=PDL::Graphics::TriD::Contours\->new($d,[$x,$y,$z],[$r,$g,$b],$options);
.Ve
.PP
where \f(CW$d\fR is a 2D pdl of data to be contoured. [$x,$y,$z] define a 3D
map of \f(CW$d\fR into the visualization space [$r,$g,$b] is an optional [3,1]
ndarray specifying the contour color and \f(CW$options\fR is a hash reference to
a list of options documented below.  Contours can also be colored by
value using the set_color_table function.
.PP
.Vb 6
\&  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 algorithm tries to
\&  choose values based on the data supplied.  Font can also be specified or
\&  overwritten by the addlabels() function below.
.Ve
.SS "\fBaddlabels()\fP"
.IX Subsection "addlabels()"
Add labels to a contour plot
.PP
.Vb 1
\&  $contour\->addlabels($labelint,$segint,$font);
.Ve
.PP
\&\f(CW$labelint\fR is the integer interval between labeled contours.  If you
have 8 contour levels and specify \f(CW$labelint\fR=3 addlabels will attempt
to label the 1st, 4th, and 7th contours.  \f(CW$labelint\fR defaults to 1.
.PP
\&\f(CW$segint\fR specifies the density of labels on a single contour
level.  Each contour level consists of a number of connected 
line segments, \f(CW$segint\fR defines how many of these segments get labels.
\&\f(CW$segint\fR defaults to 5, that is every fifth line segment will be labeled.
.SS "set_colortable($table)"
.IX Subsection "set_colortable($table)"
Sets contour level colors based on the color table.
.PP
\&\f(CW$table\fR is passed in as either an ndarray 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] ndarray.  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.
.SS "\fBcoldhot_colortable()\fP"
.IX Subsection "coldhot_colortable()"
A simple colortable function for use with the set_colortable function.
.PP
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.