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Faster support generation. Includes a new implementation of the Douglas-Peucker algorithm

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This commit is contained in:
Alessandro Ranellucci 2012-02-25 14:46:21 +01:00
parent 94e673e050
commit eba7c10018
9 changed files with 166 additions and 183 deletions
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109
lib/Slic3r/Geometry.pm
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@ -18,11 +18,10 @@ our @EXPORT_OK = qw(
polyline_remove_parallel_continuous_edges polyline_remove_acute_vertices
polygon_remove_acute_vertices polygon_remove_parallel_continuous_edges
shortest_path collinear scale unscale merge_collinear_lines
rad2deg_dir bounding_box_center line_intersects_any
rad2deg_dir bounding_box_center line_intersects_any douglas_peucker
polyline_remove_short_segments normal triangle_normal
);
use Slic3r::Geometry::DouglasPeucker qw(Douglas_Peucker);
use XXX;
use constant PI => 4 * atan2(1, 1);
@ -110,6 +109,19 @@ sub distance_between_points {
return sqrt((($p1->[X] - $p2->[X])**2) + ($p1->[Y] - $p2->[Y])**2);
}
sub point_line_distance {
my ($point, $line) = @_;
return distance_between_points($point, $line->[A])
if same_point($line->[A], $line->[B]);
my $n = ($line->[B][X] - $line->[A][X]) * ($line->[A][Y] - $point->[Y])
- ($line->[A][X] - $point->[X]) * ($line->[B][Y] - $line->[A][Y]);
my $d = sqrt((($line->[B][X] - $line->[A][X]) ** 2) + (($line->[B][Y] - $line->[A][Y]) ** 2));
return abs($n) / $d;
}
sub line_length {
my ($line) = @_;
return distance_between_points(@$line[A, B]);
@ -740,4 +752,97 @@ sub shortest_path {
return $result;
}
sub douglas_peucker {
my ($points, $tolerance) = @_;
my $results = [];
my $dmax = 0;
my $index = 0;
for my $i (1..$#$points) {
my $d = point_line_distance($points->[$i], [ $points->[0], $points->[-1] ]);
if ($d > $dmax) {
$index = $i;
$dmax = $d;
}
}
if ($dmax >= $tolerance) {
my $dp1 = douglas_peucker([ @$points[0..$index] ], $tolerance);
$results = [
@$dp1[0..($#$dp1-1)],
@{douglas_peucker([ @$points[$index..$#$points] ], $tolerance)},
];
} else {
$results = [ $points->[0], $points->[-1] ];
}
return $results;
}
sub douglas_peucker2 {
my ($points, $tolerance) = @_;
my $anchor = 0;
my $floater = $#$points;
my @stack = ();
my %keep = ();
push @stack, [$anchor, $floater];
while (@stack) {
($anchor, $floater) = @{pop @stack};
# initialize line segment
my ($anchor_x, $anchor_y, $seg_len);
if (grep $points->[$floater][$_] != $points->[$anchor][$_], X, Y) {
$anchor_x = $points->[$floater][X] - $points->[$anchor][X];
$anchor_y = $points->[$floater][Y] - $points->[$anchor][Y];
$seg_len = sqrt(($anchor_x ** 2) + ($anchor_y ** 2));
# get the unit vector
$anchor_x /= $seg_len;
$anchor_y /= $seg_len;
} else {
$anchor_x = $anchor_y = $seg_len = 0;
}
# inner loop:
my $max_dist = 0;
my $farthest = $anchor + 1;
for my $i (($anchor + 1) .. $floater) {
my $dist_to_seg = 0;
# compare to anchor
my $vecX = $points->[$i][X] - $points->[$anchor][X];
my $vecY = $points->[$i][Y] - $points->[$anchor][Y];
$seg_len = sqrt(($vecX ** 2) + ($vecY ** 2));
# dot product:
my $proj = $vecX * $anchor_x + $vecY * $anchor_y;
if ($proj < 0) {
$dist_to_seg = $seg_len;
} else {
# compare to floater
$vecX = $points->[$i][X] - $points->[$floater][X];
$vecY = $points->[$i][Y] - $points->[$floater][Y];
$seg_len = sqrt(($vecX ** 2) + ($vecY ** 2));
# dot product:
$proj = $vecX * (-$anchor_x) + $vecY * (-$anchor_y);
if ($proj < 0) {
$dist_to_seg = $seg_len
} else { # calculate perpendicular distance to line (pythagorean theorem):
$dist_to_seg = sqrt(abs(($seg_len ** 2) - ($proj ** 2)));
}
if ($max_dist < $dist_to_seg) {
$max_dist = $dist_to_seg;
$farthest = $i;
}
}
}
if ($max_dist <= $tolerance) { # use line segment
$keep{$_} = 1 for $anchor, $floater;
} else {
push @stack, [$anchor, $farthest];
push @stack, [$farthest, $floater];
}
}
return [ map $points->[$_], sort keys %keep ];
}
1;