# draw a skewed rectange for each data-point

#     ____
#    G p  D \
#   / o / | |
#  B_t_C  | | 
# |       | +-- $val_height
# | face  | |
# |       | /
# |       E \ 
# |      /  +-- $slant_height
# A____F/   /
#
# \-+-/ \+/
#   |    |
# $ppd   - $consts{slant}

##</code><code>##

if ($params->{dim} == 3) {
  my $face = GD::Polygon->new;
  A: $face->addPt($x_pos, $yi + $val_height - 1);
  B: $face->addPt($x_pos, $yi + $slant_height);
  C: $face->addPt($x_pos + $ppd, $yi + $slant_height);
  D: $face->addPt($x_pos + $ppd + $consts{slant}, $yi);
  E: $face->addPt($x_pos + $ppd + $consts{slant}, $yi + $val_height - $slant_height - 1);  # E
  F: $face->addPt($x_pos + $ppd, $yi + $val_height - 1);
  $image->filledPolygon($face,$hist_front{"@$cRGB"});

  my $top = GD::Polygon->new;
  B: $top->addPt($x_pos, $yi + $slant_height);
  G: $top->addPt($x_pos + $consts{slant}, $yi);
  D: $top->addPt($x_pos + $ppd + $consts{slant}, $yi);
  C: $top->addPt($x_pos + $ppd, $yi + $slant_height);
  $image->filledPolygon($top,$hist_top{"@$cRGB"});
}