#!/usr/bin/perl -w
#
# usage:
#   ./distort-stl <INPUT >OUTPUT DISTORTION [PARAMS...] ...
#
# DISTORTIONs:
#
#   project-cylinder RADIUS
#       projects the X-Z plane onto the cylinder of
#           radius RADIUS with axis [0, 0, t]
#       origin becomes [0, -RADIUS, 0]
#       other planes of the input are projected onto smaller
#           or larger cylinders accordingly
#       probably a bad idea if
#           object has any Y > RADIUS
#           object has any |X| > tau / RADIUS
#       technically, treats input as if it were
#       polar-rectangular coords:
#          Z' = Z; R' = Y + RADIUS; theta' = X / RADIUS
#       and then converts back into cartesian

use strict;
use autodie;

sub shift_arg () {
    die unless @ARGV;
    scalar shift @ARGV;
}

sub pointmap_distortion {
    my ($x,$y,$z) = @_;
    my $radius = shift_arg;
    my $r = $y + $radius;
    my $theta = $x / $radius;
    return ($r * cos($theta),
	    $r * sin($theta),
	    $z);
}

if (@ARGV && $ARGV[0] =~ m/^-/) {
    die "no options supported\n";
}

my $admesh_pipe = '--write-ascii-stl 3<&0 4>&1 >/dev/null /dev/fd/4 /dev/fd/3';

open I, "admesh $admesh_pipe |";
open O, "| admesh --normal-values $admesh_pipe";

our @saved_argv = @ARGV;

while (<I>) {
    if (s/^\s+vertex\s+//) {
	my $lhs = $&;
	s/\s+$//;
	my @xyz = split /\s+/, $_;
	while (@ARGV) {
	    my $op = shift_arg;
	    @xyz = &{ $::{"pointmap_$op"} }( @xyz );
	}
	@xyz = map { sprintf "%.18g", $_ } @xyz;
	$_ = "$lhs@xyz\n";
    }
    print O;
}

<I>,<O> if 0; # suppresses Name "main::I" used only once

close I;
close O;