From c5514926e454f2f2b56d7cf95c09b31b4580d2b1 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 7 Jan 2018 23:05:50 +0000
Subject: [PATCH] distort-stl: seems to work now

---
 distort-stl | 53 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/distort-stl b/distort-stl
index 9dab4ed..39e5a15 100755
--- a/distort-stl
+++ b/distort-stl
@@ -34,7 +34,8 @@ sub TAU () { M_PI * 2; }
 
 our $fa = 10;
 
-our @triangles;
+our $triangles;
+our $output;
 
 sub shift_arg () {
     die unless @ARGV;
@@ -66,11 +67,30 @@ sub subdivide_triangle ($$) {
     $fn->(\@mids);
 }
 
+sub append_triangle ($) {
+    my ($t) = @_;
+    push @$output, $t;
+}
+
 #---------- project-cylinder ----------
 
 our $project_cylinder_radius;
 our $project_cylinder_max_d_theta;
 
+sub project_cylinder_need_subdivide () {
+    foreach my $t (@$triangles) {
+	my @thetas = map { $_->[0] / $project_cylinder_radius } @$t;
+
+	foreach my $ix (0..2) {
+	    if (abs($thetas[$ix] - $thetas[($ix+1)%3])
+		> $project_cylinder_max_d_theta) {
+		return 1;
+	    }
+	}
+    }
+    return 0;
+}
+
 sub project_cylinder_tri {
     my ($t) = @_;
 
@@ -78,16 +98,6 @@ sub project_cylinder_tri {
 
     my $radius = $project_cylinder_radius;
 
-    my @thetas = map { $_->[0] / $radius } @$t;
-
-    foreach my $ix (0..2) {
-	if (abs($thetas[$ix] - $thetas[($ix+1)%3])
-	    > $project_cylinder_max_d_theta) {
-	    subdivide_triangle $t, \&project_cylinder_tri;
-	    return;
-	}
-    }
-
     my @ot;
     foreach my $p (@$t) {
 	my ($x,$y,$z) = @$p;
@@ -97,17 +107,26 @@ sub project_cylinder_tri {
 		    -$r * cos($theta),
 		    $z ];
     }
-    push @triangles, \@ot;
+    append_triangle \@ot;
 }
 
 sub op__project_cylinder () {
     $project_cylinder_radius = shift_arg;
     $project_cylinder_max_d_theta = $fa * TAU/360;
 
-    my @input = (@triangles);
-    @triangles = ();
+    while (project_cylinder_need_subdivide()) {
+	$output = [];
+	foreach my $t (@$triangles) {
+	    subdivide_triangle $t, \&append_triangle;
+	}
+	$triangles = $output;
+    }
 
-    project_cylinder_tri $_ foreach @input;
+    $output = [];
+    foreach my $t (@$triangles) {
+	project_cylinder_tri $t;
+    }
+    $triangles = $output;
 }
 
 #---------- main program ----------
@@ -156,7 +175,7 @@ while (<I>) {
 	push @$triangle, \@xyz;
     } elsif (m/^endloop/) {
 	die unless @$triangle == 3;
-	push @triangles, $triangle;
+	push @$triangles, $triangle;
 	undef $triangle;
     } elsif (m/^(?:solid|facet\s+normal|endfacet|endsolid)\s/) {
     } else {
@@ -177,7 +196,7 @@ select $otmp;
 
 print "solid distort-stl\n";
 
-foreach my $t (@triangles) {
+foreach my $t (@$triangles) {
     print "  facet normal 0 0 0\n";
     print "    outer loop\n";
     die unless @$t==3;
-- 
2.30.2