+#no warnings qw(recursion);
+
+sub sprintf_triangle ($) {
+ my ($t) = @_;
+
+ return '' unless $debug;
+
+ if ($ps && $t->[3] =~ m/$ENV{DISTORT_PS_RE}/) {
+ printf PS <<'END',
+ %20.16g %20.16g %20.16g moveto
+ %20.16g %20.16g %20.16g lineto
+ %20.16g %20.16g %20.16g lineto
+ closepath stroke
+END
+ $t->[0][0], $t->[0][1], $t->[0][2],
+ $t->[1][0], $t->[1][1], $t->[1][2],
+ $t->[2][0], $t->[2][1], $t->[2][2],
+ or die $!;
+ flush PS or die $!;
+ }
+
+ sprintf
+ "%11.6f,%11.6f,%11.6f / ".
+ "%11.6f,%11.6f,%11.6f / ".
+ "%11.6f,%11.6f,%11.6f %-40s ",
+ $t->[0][0], $t->[0][1], $t->[0][2],
+ $t->[1][0], $t->[1][1], $t->[1][2],
+ $t->[2][0], $t->[2][1], $t->[2][2],
+ $t->[3];
+}
+
+sub maybe_subdivide_triangle ($$$$) {
+ my ($t, $ok, $changed, $edge_need_subdivide_fn) = @_;
+
+ print STDERR sprintf_triangle $t if $debug;
+
+ my (@longest) = qw(-1);
+
+ foreach my $ix (0..2) {
+ my $jx = ($ix+1) % 3;
+ next unless $edge_need_subdivide_fn->($t->[$ix], $t->[$jx]);
+ my $l2 = 0;
+ foreach my $ci (0..2) {
+ my $d = $t->[$ix][$ci] - $t->[$jx][$ci];
+ $l2 += $d*$d;
+ }
+ next unless $l2 > $longest[0];
+ @longest = ($l2, $ix, $jx);
+ }
+ if ($longest[0] < 0) {
+ push @$ok, $t;
+ printf STDERR "OK nok=%d nchanged=%d\n",
+ (scalar @$ok), (scalar @$changed)
+ if $debug;
+ print STDERR Dumper(\@$ok) if $debug>=2;
+ return;
+ }
+ my ($dummy,$ix,$jx) = @longest;
+ my $kx = ($ix+2) % 3;
+
+ printf STDERR
+ " S i=%d j=%d k=%d ",
+ $ix, $jx, $kx
+ if $debug;
+ my @midp;
+ foreach my $ci (0..2) {
+ push @midp, 0.5 * ($t->[$ix][$ci] + $t->[$jx][$ci]);
+ }
+
+ printf STDERR
+ " midp %11.6f,%11.6f,%11.6f\n",
+ @midp
+ if $debug;
+
+ # triangle i-j-k, splitting edge i-m
+ # gives i-m-k, k-m-j
+ my $gensplit = sub {
+ my ($ixjx, $xwhat) = @_;
+ my $n = [ @$t ];
+ $n->[$ixjx] = \@midp;
+ $n->[3] = "$t->[3]$xwhat";
+ printf STDERR "%s\n", sprintf_triangle $n if $debug;
+ unshift @$changed, $n;
+ };
+ $gensplit->($ix, "a$ix$jx");
+ $gensplit->($jx, "b$ix$jx");
+ return;
+}
+
+sub maybe_subdivide ($) {
+ my ($edge_need_subdivide_fn) = @_;
+
+ my @small_enough = ();
+ while (my $t = shift @$triangles) {
+ maybe_subdivide_triangle $t, \@small_enough, $triangles,
+ $edge_need_subdivide_fn;
+ }
+
+ $triangles = \@small_enough;
+}
+
+sub append_triangle ($) {
+ my ($t) = @_;
+ push @$output, $t;
+}
+
+#---------- set-fa ----------
+
+sub op__set_fa () {
+ $fa = shift_arg;
+}
+
+#---------- project-cylinder ----------
+
+our $project_cylinder_radius;
+our $project_cylinder_max_d_theta;
+
+sub project_cylinder_edge_need_subdivide ($$) {
+ my @thetas = map { $_->[0] / $project_cylinder_radius } @_;
+ return abs($thetas[0] - $thetas[1]) > $project_cylinder_max_d_theta;