Thank you for your advice.
I think i can get good results creating a larger image and then scaling it down with something like this:
#this is the default example for GD::Graph3D
use GD::Graph::bars3d;
use Image::Magick;
my @data = (
["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
[ 1203, 3500, 3973, 2859, 3012, 3423, 1230]
);
my $graph = new GD::Graph::bars3d( 800, 600 ); #BIG image
$graph->set(
x_label => 'Day of the week',
y_label => 'Number of hits',
title => 'Daily Summary of Web Site',
);
my $gd = $graph->plot( \@data );
#here the interesting part
my $image=Image::Magick->new(magick=>'png');
$image->BlobToImage($gd->png);
$image->Resize(width=>400, height=>300); #small and anti-aliased one
$image->Write('graph3d.png');
gkinueliileunikg