Slic3r/lib/Slic3r/ExPolygon.pm

package Slic3r::ExPolygon;
use strict;
use warnings;

# an ExPolygon is a polygon with holes

use List::Util qw(first);
use Math::Geometry::Voronoi;
use Slic3r::Geometry qw(X Y A B point_in_polygon epsilon scaled_epsilon);
use Slic3r::Geometry::Clipper qw(union_ex diff_pl);

sub wkt {
    my $self = shift;
    return sprintf "POLYGON(%s)", 
        join ',', map "($_)", map { join ',', map "$_->[0] $_->[1]", @$_ } @$self;
}

sub dump_perl {
    my $self = shift;
    return sprintf "[%s]", 
        join ',', map "[$_]", map { join ',', map "[$_->[0],$_->[1]]", @$_ } @$self;
}

sub offset {
    my $self = shift;
    return Slic3r::Geometry::Clipper::offset(\@$self, @_);
}

sub offset_ex {
    my $self = shift;
    return Slic3r::Geometry::Clipper::offset_ex(\@$self, @_);
}

sub noncollapsing_offset_ex {
    my $self = shift;
    my ($distance, @params) = @_;
    
    return $self->offset_ex($distance + 1, @params);
}

sub bounding_box {
    my $self = shift;
    return $self->contour->bounding_box;
}

# this method only works for expolygons having only a contour or
# a contour and a hole, and not being thicker than the supplied 
# width. it returns a polyline or a polygon
sub ____medial_axis {
    my ($self, $width) = @_;
    return $self->_medial_axis_voronoi($width);
}

sub _medial_axis_clip {
    my ($self, $width) = @_;
    
    my $grow = sub {
        my ($line, $distance) = @_;
        
        my $line_clone = $line->clone;
        $line_clone->clip_start(scaled_epsilon);
        return () if !$line_clone->is_valid;
        $line_clone->clip_end(scaled_epsilon);
        return () if !$line_clone->is_valid;
        
        my ($a, $b) = @$line_clone;
        my $dx = $a->x - $b->x;
        my $dy = $a->y - $b->y; #-
        my $dist = sqrt($dx*$dx + $dy*$dy);
        $dx /= $dist;
        $dy /= $dist;
        return Slic3r::Polygon->new(
            Slic3r::Point->new($a->x + $distance*$dy, $a->y - $distance*$dx), #--
            Slic3r::Point->new($b->x + $distance*$dy, $b->y - $distance*$dx), #--
            Slic3r::Point->new($b->x - $distance*$dy, $b->y + $distance*$dx), #++
            Slic3r::Point->new($a->x - $distance*$dy, $a->y + $distance*$dx), #++
        );
    };
    
    my @result = ();
    my $covered = [];
    foreach my $polygon (@$self) {
        my @polylines = ();
        foreach my $line (@{$polygon->lines}) {
            # remove the areas that are already covered from this line
            my $clipped = diff_pl([$line->as_polyline], $covered);
            
            # skip very short segments/dots
            @$clipped = grep $_->length > $width/10, @$clipped;
            
            # grow the remaining lines and add them to the covered areas
            push @$covered, map $grow->($_, $width*1.1), @$clipped;
            
            # if the first remaining segment is connected to the last polyline, append it 
            # to that -- FIXME: this assumes that diff_pl()
            # preserved the orientation of the input linestring but this is not generally true
            if (@polylines && @$clipped && $clipped->[0]->first_point->distance_to($polylines[-1]->last_point) <= $width/10) {
                $polylines[-1]->append_polyline(shift @$clipped);
            }
            push @polylines, @$clipped;
        }
        
        foreach my $polyline (@polylines) {
            # if this polyline looks like a closed loop, return it as a polygon
            if ($polyline->first_point->coincides_with($polyline->last_point)) {
                next if @$polyline == 2;
                $polyline->pop_back;
                push @result, Slic3r::Polygon->new(@$polyline);
            } else {
                push @result, $polyline;
            }
        }
    }
    
    return @result;
}

my $voronoi_lock :shared;

sub _medial_axis_voronoi {
    my ($self, $width) = @_;
    
    lock($voronoi_lock);
    
    my $voronoi;
    {
        my @points = ();
        foreach my $polygon (@$self) {
            {
                my $p = $polygon->pp;
                Slic3r::Geometry::polyline_remove_short_segments($p, $width / 2);
                $polygon = Slic3r::Polygon->new(@$p);
            }
            
            # subdivide polygon segments so that we don't have anyone of them
            # being longer than $width / 2
            $polygon = $polygon->subdivide($width/2);
            
            push @points, @{$polygon->pp};
        }
        $voronoi = Math::Geometry::Voronoi->new(points => \@points);
    }
    
    $voronoi->compute;
    my $vertices = $voronoi->vertices;
    
    my @skeleton_lines = ();
    foreach my $edge (@{ $voronoi->edges }) {
        # ignore lines going to infinite
        next if $edge->[1] == -1 || $edge->[2] == -1;
        
        my $line = Slic3r::Line->new($vertices->[$edge->[1]], $vertices->[$edge->[2]]);
        next if !$self->contains_line($line);
        
        # contains_point() could be faster, but we need an implementation that
        # reliably considers points on boundary
        #next if !$self->contains_point(Slic3r::Point->new(@{$vertices->[$edge->[1]]}))
        #     || !$self->contains_point(Slic3r::Point->new(@{$vertices->[$edge->[2]]}));
        
        push @skeleton_lines, [$edge->[1], $edge->[2]];
    }
    return () if !@skeleton_lines;
    
    # now walk along the medial axis and build continuos polylines or polygons
    my @polylines = ();
    {
        my @lines = @skeleton_lines;
        push @polylines, [ map @$_, shift @lines ];
        CYCLE: while (@lines) {
            for my $i (0..$#lines) {
                if ($lines[$i][0] == $polylines[-1][-1]) {
                    push @{$polylines[-1]}, $lines[$i][1];
                } elsif ($lines[$i][1] == $polylines[-1][-1]) {
                    push @{$polylines[-1]}, $lines[$i][0];
                } elsif ($lines[$i][1] == $polylines[-1][0]) {
                    unshift @{$polylines[-1]}, $lines[$i][0];
                } elsif ($lines[$i][0] == $polylines[-1][0]) {
                    unshift @{$polylines[-1]}, $lines[$i][1];
                } else {
                    next;
                }
                splice @lines, $i, 1;
                next CYCLE;
            }
            push @polylines, [ map @$_, shift @lines ];
        }
    }
    
    my @result = ();
    my $simplify_tolerance = $width / 7;
    foreach my $polyline (@polylines) {
        next unless @$polyline >= 2;
        
        # now replace point indexes with coordinates
        my @points = map Slic3r::Point->new(@{$vertices->[$_]}), @$polyline;
        
        if ($points[0]->coincides_with($points[-1])) {
            next if @points == 2;
            push @result, @{Slic3r::Polygon->new(@points[0..$#points-1])->simplify($simplify_tolerance)};
        } else {
            push @result, Slic3r::Polyline->new(@points);
            $result[-1]->simplify($simplify_tolerance);
        }
    }
    
    return @result;
}

package Slic3r::ExPolygon::Collection;
use Slic3r::Geometry qw(X1 Y1);

sub size {
    my $self = shift;
    return [ Slic3r::Geometry::size_2D([ map @$_, map @$_, @$self ]) ];
}

1;