-sub pointmap_project_cylinder {
- my ($x,$y,$z) = @_;
- my $radius = shift_arg;
- my $r = $radius - $y;
- my $theta = $x / $radius;
- return ($r * sin($theta),
- -$r * cos($theta),
- $z);
+sub subdivide_triangle ($$) {
+ my ($it, $fn) = @_;
+ my @mids;
+ foreach my $ix (0..2) {
+ my $jx = ($ix+1) % 3;
+ my @midp;
+ foreach my $ci (0..2) {
+ push @midp, 0.5 * ($it->[$ix][$ci] + $it->[$jx][$ci]);
+ }
+ push @mids, @midp;
+ }
+ foreach my $ix (0..2) {
+ my $kx = ($ix+2) % 3;
+ $fn->([ $it->[$ix], $mids[$ix], $it->[$kx] ]);
+ }
+ $fn->(\@mids);
+}
+
+#---------- project-cylinder ----------
+
+our $project_cylinder_radius;
+our $project_cylinder_max_d_theta;
+
+sub project_cylinder_tri {
+ my ($it) = @_;
+
+ my $radius = project_cylinder_radius;
+
+ my @thetas = map { $_->[0] / $radius } @$it;
+
+ foreach my $ix (0..2) {
+ if (abs($thetas[$ix] - $thetas[($ix+1)%3])
+ > $project_cylinder_max_d_theta) {
+ subdivide_triangle $it, \&project_cylinder_tri;
+ return;
+ }
+ }
+
+ my @ot;
+ foreach my $p (@it) {
+ my ($x,$y,$z) = @$p;
+ my $r = $radius - $y;
+ my $theta = $x / $radius;
+ push @ot, [ $r * sin($theta),
+ -$r * cos($theta),
+ $z ];
+ }
+ push @triangles, \@ot;
+}
+
+sub op__project_cylinder () {
+ $project_cylinder_radius = shift_arg;
+ $project_cylinder_max_d_theta = $fa * TAU/360;
+
+ my @input = (@triangles);
+ @triangles = ();
+
+ project_cylinder_tri $_ foreach @input;