From 0b7257ca44cddaf016c96b1998fe34b99d1701b6 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 7 Jan 2018 21:44:52 +0000
Subject: [PATCH] distort-stl: new approach

---
 distort-stl | 122 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 103 insertions(+), 19 deletions(-)

diff --git a/distort-stl b/distort-stl
index 4820e03..eb3a7a1 100755
--- a/distort-stl
+++ b/distort-stl
@@ -18,27 +18,87 @@
 #       polar-rectangular coords:
 #          Z' = Z; R' = Y + RADIUS; theta' = X / RADIUS
 #       and then converts back into cartesian
+#       honours fa but not fs or fn
+#
+#   set-fa $FA
 
 use strict;
 use autodie;
 
 use File::Temp;
+use List::Util;
+
+our $fa = 10;
+
+our @triangles;
 
 sub shift_arg () {
     die unless @ARGV;
     scalar shift @ARGV;
 }
 
-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;
 }
 
+#---------- main program ----------
+
 if (@ARGV && $ARGV[0] =~ m/^-/) {
     die "no options supported\n";
 }
@@ -52,28 +112,52 @@ my $admesh_stdout = '--write-ascii-stl /dev/fd/3 3>&1 >/dev/null';
 
 open I, "admesh $admesh_stdout $itmp |";
 
-our @saved_argv = @ARGV;
+my $triangle;
 
 while (<I>) {
-    @ARGV = @saved_argv;
-    if (s/^\s+vertex\s+//) {
+    if (m/^\s+outer\s+loop/) {
+	die if $triangle;
+	$triangle = [];
+    } elsif (s/^\s+vertex\s+//) {
 	my $lhs = $&;
 	s/\s+$//;
 	my @xyz = split /\s+/, $_;
-	while (@ARGV) {
-	    my $op = shift_arg;
-	    $op =~ y/-/_/;
-	    @xyz = &{ ${*::}{"pointmap_$op"} }( @xyz );
-	}
-	@xyz = map { sprintf "%.18g", $_ } @xyz;
-	$_ = "$lhs@xyz\n";
+	die unless $triangle;
+	push @$triangle, \@xya;
+    } elsif (m/^\s+endloop/) {
+	die unless @$triangle == 3;
+	push @triangles, $triangle;
+    } elsif (m/^\s+(?:solid|facet\s+normal|endfacet|endsolid)\s/) {
+    } else {
+	die "$_ ?";
     }
-    print $otmp $_;
 }
 
 close I;
 <I> if 0; # suppresses Name "main::I" used only once
 
+while (@ARGV) {
+    my $op = shift_arg;
+    $op =~ y/-/_/;
+    &{ ${*::}{"op__$op"} };
+}
+
+select $otmp;
+
+print "solid distort-stl\n";
+
+foreach my $t (@triangles) {
+    print "  facet normal 0 0 0\n";
+    print "    outer loop\n";
+    print "      vertex";
+    printf " %.18g", $_ foreach @$t;
+    print "\n";
+    print "    endloop\n";
+    print "  endfacet\n";
+}
+
+print "endsolid distort-stl\n";
+
 flush $otmp;
 
 system "admesh --normal-values $admesh_stdout $otmp";
-- 
2.30.2